Mesoporous PdN Alloy Nanocubes for Efficient Electrochemical Nitrate Reduction to Ammonia

Spatially Separated Cu/Ru on Ordered Mesoporous Carbon for Superior Ammonia Electrosynthesis from Nitrate over a Wide Potential Window

Nitrate (NO3-) in wastewater poses a serious threat to human health and the ecological environment. The electrocatalytic NO3- reduction to ammonia (NH3) reaction (NO3-RR) emerges as a promising carbon-free energy route for enabling NO3- removal and sustainable NH3 synthesis. However, it remains a challenge to achieve high Faraday efficiencies at a wide potential window due to the complex multiple-electron reduction process. Herein, spatially separated dual-metal tandem electrocatalysts made of a nitrogen-doped ordered mesoporous carbon support with ultrasmall and high-content Cu nanoparticles encapsulated inside and large and low-content Ru nanoparticles dispersed on the external surface (denoted as Ru/Cu@NOMC) are designed. In electrocatalytic NO3-RR, the Cu sites can quickly convert NO3- to adsorbed NO2- (*NO2-), while the Ru sites can efficiently produce active hydrogen (*H) to enhance the kinetics of converting *NO2- to NH3 on the Cu sites. Due to the synergistic effect between the Cu and Ru sites, Ru/Cu@NOMC exhibits a maximum NH3 Faradaic efficiency (FENH3) of approximately 100% at -0.1 V vs reversible hydrogen electrode (RHE) and a high NH3 yield rate of 1267 mmol gcat-1 h-1 at -0.5 V vs RHE. Finite element method (FEM) simulation and electrochemical in situ Raman spectroscopy revealed that the mesoporous framework can enhance the intermediate concentration due to the in situ confinement effect. Thanks to the Cu-Ru synergistic effect and the mesopore confinement effect, a wide potential window of approximately 500 mV for FENH3 over 90% and a superior stability for NH3 production over 156 h can be achieved on the Ru/Cu@NOMC catalyst.

Polyphosphide anion-mediated simultaneous P, Au co-alloying with Pd for anti-poisoning formic acid oxidation

An innovative polyphosphide route is developed to synthesize a series of P-doped PdAu ternary alloys. The alloying of P and Au optimizes the electronic structure and reduces the back-donation of d electrons to CO. Meanwhile, the generation of CO is largely inhibited by the highly selective direct pathway arising from the synergistic electron/ligand effect of Au and P, leading to a remarkable anti-poisoning capability for formic acid oxidation.

Homogeneously Mixed Cu-Co Bimetallic Catalyst Derived from Hydroxy Double Salt for Industrial-Level High-Rate Nitrate-to-Ammonia Electrosynthesis

Electrocatalytic nitrate reduction reaction (NO3RR) presents an innovative approach for sustainable NH3 production. However, selective NH3 production is hindered by the multiple intermediates involved in the NO3RR process and the competitive hydrogen evolution reaction. Hence, the development of highly efficient NO3RR catalysts is paramount. Herein, we report highly efficient bimetallic catalysts derived from hydroxy double salt (HDS). Under NO3RR conditions, Cu1Co1-HDS undergoes in situ reconstruction, forming nanocomposites of homogeneously distributed metallic Cu0 and Co(OH)2. Reconstruction-induced Cu0 rapidly converts NO3- to NO2-, which is further hydrogenated to NH3 by Co(OH)2. Homogeneously mixed Cu and Co species maximize this synergistic effect, achieving outstanding NO3RR performance including the highest NH3 yield rate (4.625 mmol h-1 cm-2) reported for powder-type NO3RR catalysts. Integration of Cu1Co1-HDS with a commercial Si solar cell attained 4.53% solar-to-ammonia efficiency from industrial wastewater-level concentrations of NO3- (2000 ppm), demonstrating practical application potential for solar-driven NH3 production. This study provides a strategy for enhancing the NH3 yield rate by optimizing the compositions and distributions of Cu and Co.

Efficient Electroreduction of Low Nitrate Concentration via Nitrate Self-Enrichment and Active Hydrogen Inducement on the Ce(IV)-Co3O4 Cathode

Low concentrations of nitrate (NO3-) widely exist in wastewater, post-treated wastewater, and natural environments; its further disposal is a challenge but meaningful for its discharge goals. Electroreduction of NO3- is a promising method that allows to eliminate NO3- and even generate higher-value NH3. However, the massive side reaction of hydrogen evolution has raised great obstacles in the electroreduction of low concentrations of NO3-. Herein, we present an efficient electroreduction method for low or even ultralow concentrations of NO3- via NO3- self-enrichment and active hydrogen (H*) inducement on the Ce(IV)-Co3O4 cathode. The key mechanism is that the strong oxytropism of Ce(IV) in Co3O4 resulted in two changes in structures, including loose nanoporous structures with copious dual adsorption sites of Ce-Co showing strong self-enrichment of NO3- and abundant oxygen vacancies (Ovs) inducing substantial H*. Ultimately, the bifunctional role synergistically promoted the selective conversion of NH3 rather than H2. As a result, Ce(IV)-Co3O4 demonstrated a NO3- self-enrichment with a 4.3-fold up-adsorption, a 7.5-fold enhancement of NH3 Faradic efficiency, and a 93.1% diminution of energy consumption when compared to Co3O4, substantially exceeding other reported electroreduction cathodes for NO3- concentrations lower than 100 mg·L-1. This work provides an effective treatment method for low or even ultralow concentrations of NO3-.

Electrosynthesis of Ammonia from Nitrate Using a Self-Activated Carbon Fiber Paper

While electrochemically upcycling nitrate wastes to valuable ammonia is considered a very promising pathway for tackling the environmental and energy challenges underlying the nitrogen cycle, the effective catalysts involved are mainly limited to metal-based materials. Here, we report that commercial carbon fiber paper, which is a classical current collector and is typically assumed to be electrochemically inert, can be significantly activated during the reaction. As a result, it shows a high NH3 Faradaic efficiency of 87.39% at an industrial-level current density of 300 mA cm-2 for over 90 h of continuous operation, with a NH3 production rate of as high as 1.22 mmol cm-2 h-1. Through experimental and theoretical analysis, the in situ-formed oxygen functional groups are demonstrated to be responsible for the NO3RR performance. Among them, the C-O-C group is finally identified as the active center, which lowers the thermodynamic energy barrier and simultaneously improves the hydrogenation kinetics. Moreover, high-purity NH4Cl and NH3·H2O were obtained by coupling the NO3RR with an air-stripping approach, providing an effective way for converting nitrate waste into high-value-added NH3 products.

An ultrasensitive electrochemical immunosensor based on meso-PdN NCs and Au NPs/N-CNTs for quantitative cTnI detection

Electrochemical immunosensors have gained considerable attention in detecting human disease markers due to their excellent specificity, high sensitivity, and facile operation. Herein, a rational-designed sandwich-type electrochemical immunosensor is constructed for the sensitive detection of cardiac troponin I (cTnI) using nitrogen-doped carbon nanotubes loaded with gold nanoparticles (Au NPs/N-CNTs) as substrate and highly active mesoporous palladium-nitrogen nanocubes (meso-PdN NCs) as secondary antibody markers. Benefitting from its large specific surface area (638.04 m2 g-1) and high nitrogen content, novel polydopamine (PDA)/ halloysite nanotubes (HNTs) hybrid derived one-dimensional (1D) N-CNTs can provide more binding sites for the in-situ growth of Au NPs to connect Ab1. Furthermore, as an ideal substrate material, Au NPs/N-CNTs exhibit finely tuned mesoporous structures and outstanding conductivity, which facilitate the mass and electron transfer during the electrocatalysis process. Besides, highly concave surfaces and crystalline mesopores of meso-PdN NCs expose more surfaces and crevices, providing abundant reactive sites for H2O2 reduction. Remarkably, the as-obtained immunosensor presented a wide linear range (from 10 fg mL-1 to 100 ng mL-1) and an excellent low detection limit (9.85 fg mL-1). This study may offer new insights into the precise fabrication of efficient electrochemical immunosensors for various clinical diagnosis applications.

2D PtRhPb Mesoporous Nanosheets with Surface-Clean Active Sites for Complete Ethanol Oxidation Electrocatalysis

The development of active and selective metal electrocatalysts for complete ethanol oxidation reaction (EOR) into desired C1 products is extremely promising for practical application of direct ethanol fuel cells. Despite some encouraging achievements, their activity and selectivity remain unsatisfactory. In this work, it is reported that 2D PtRhPb mesoporous nanosheets (MNSs) with anisotropic structure and surface-clean metal site perform perfectly for complete EOR electrocatalysis in both three-electrode and two-electrode systems. Different to the traditional routes, a selective etching strategy is developed to produce surface-clean mesopores while retaining parent anisotropy quasi-single-crystalline structure without the mesopore-forming surfactants. This method also allows the general synthesis of surface-clean mesoporous metals with other compositions and structures. When being performed for alkaline EOR electrocatalysis, the best PtRhPb MNSs deliver remarkably high activity (7.8 A mg-1) and superior C1 product selectivity (70% of Faradaic efficiency), both of which are much better than reported electrocatalysts. High performance is assigned to multiple structural and compositional synergies that not only stabilized key OHads intermediate by surface-clean mesopores but also separated the chemisorption of two carbons in ethanol by adjacent Pt and Rh sites, which facilitate the oxidation cleavage of stable C─C bond for complete EOR electrocatalysis.

Interstitial Boron Atoms in Pd Aerogel Selectively Switch the Pathway for Glycolic Acid Synthesis from Waste Plastics

Electro-reforming of poly(ethylene terephthalate) (PET) into valuable chemicals is garnering significant attention as it opens a mild avenue for waste resource utilization. However, achieving high activity and selectivity for valuable C2 products during ethylene glycol (EG) oxidation in PET hydrolysate on Pd electrocatalysts remains challenging. The strong interaction between Pd and carbonyl (*CO) intermediates leads to undesirable over-oxidation and poisoning of Pd sites, which hinders the highly efficient C2 products production. Herein, a nonmetallic alloying strategy is employed to fabricate a Pd-boron alloy aerogel (PdB), wherein B atoms are induced to regulate the electron structure and surface oxophilicity. This approach allows a remarkable mass activity of 6.71 A mgPd -1, glycolic acid (GA) Faradaic efficiency (FE) of 93.8%, and stable 100 h cyclic electrolysis. In situ experiments and density functional theory calculations reveal the contributions of B inserted in Pd lattice on highly effective EG-to-GA conversion. Interestingly, the heightened surface oxophilicity and regulated electronic structure by B incorporation weakened *CO intermediates adsorption and enhanced hydroxyl species affinity to accelerate oxidative *OH adspecies formation, thereby synergistically avoiding over-oxidation and boosting GA synthesis. This work provides valuable insights for the rational design of high-performance electrocatalysts for GA synthesis via an oxophilic B motifs incorporation strategy.

Charge Redistribution in High-Entropy Perovskite Oxide Porous Nanotubes Boosts Nitrate Electroreduction to Ammonia

High-entropy perovskite oxides are promising materials in the field of electrocatalysis due to their advantages such as large spatial composition regulation, entropy effects, and tunable material properties. However, the preparation of high-entropy perovskite oxides with stable and controllable structures still remains challenging. Herein, we fabricated a series of high-entropy perovskite oxide porous nanotubes (PNTs) by electrospinning as efficient electrocatalysts for the nitrate reduction reaction (NO3RR). We further revealed that the different diffusion and decomposition behaviors of metal ions and polymers during the calcination process are the key to the formation of high-entropy perovskite oxide PNTs. Especially, LaSrNiCoMnFeCuO3 PNTs show excellent performance of the NO3RR, achieving the maximum NH3 Faradaic efficiency of almost 100%, yield rate of 1657.5 μg h-1 mgcat.-1, and durable stability after successive cycling, being one of the best electrocatalysts for the NO3RR. The mechanism studies show that the charge redistribution induced by the multisite synergistic effect and abundant unsaturated sites in the high-entropy perovskite oxide PNTs favors the adsorption of NO3- and key intermediates and reduces the catalytic energy barrier, thus further achieving high NO3- conversion efficiency.

Electrocatalytic Valorization of Nitrate and Polyester Plastic for Simultaneous Production of Ammonia and Glycolic Acid

Electrochemical upcycling of nitrate and polyester plastic into valuable products is an ideal solution to realize the resource utilization. Here, the co-production of ammonia (NH3) and glycolic acid (GA) via electrochemical upcycling of nitrate and polyethylene terephthalate (PET) plastics over mesoporous Pd3Au film on Ni foam (mPd3Au/NF), which is synthesized by micelle-assisted replacement method, is proposed. The mPd3Au/NF with well-developed mesoporous structure provides abundant active sites and facilitated transfer channels and strong electronic effect. As such, the mPd3Au/NF exhibits high Faraday efficiencies of 97.28% and 95.32% at 0.9 V for the formation of NH3 and GA, respectively. Theoretical results indicate that the synergistic effect of Pd and Au can optimize adsorption energy of key intermediates *NOH and *OCH2-CH2OH on active sites and increase bond energy of C─C band, thereby improving the activity and selectivity for the formation of NH3 and GA. This work proposes a promising strategy for the simultaneous conversation of nitrate and PET plastic into high-value NH3 and GA.

Alloying and confinement effects on hierarchically nanoporous CuAu for efficient electrocatalytic semi-hydrogenation of terminal alkynes

Electrocatalytic alkynes semi-hydrogenation to produce alkenes with high yield and Faradaic efficiency remains technically challenging because of kinetically favorable hydrogen evolution reaction and over-hydrogenation. Here, we propose a hierarchically nanoporous Cu50Au50 alloy to improve electrocatalytic performance toward semi-hydrogenation of alkynes. Using Operando X-ray absorption spectroscopy and density functional theory calculations, we find that Au modulate the electronic structure of Cu, which could intrinsically inhibit the combination of H* to form H2 and weaken alkene adsorption, thus promoting alkyne semi-hydrogenation and hampering alkene over-hydrogenation. Finite element method simulations and experimental results unveil that hierarchically nanoporous catalysts induce a local microenvironment with abundant K+ cations by enhancing the electric field within the nanopore, accelerating water electrolysis to form more H*, thereby promoting the conversion of alkynes. As a result, the nanoporous Cu50Au50 electrocatalyst achieves highly efficient electrocatalytic semi-hydrogenation of alkynes with 94% conversion, 100% selectivity, and a 92% Faradaic efficiency over wide potential window. This work provides a general guidance of the rational design for high-performance electrocatalytic transfer semi-hydrogenation catalysts.

Construction of H-Doped PdB Nanocrystals as Electrocatalysts to Modulate Formic Acid Oxidation

The strong ligand effect in B-doped Pd-based (PdB) catalysts renders them a promising anode for constructing formic acid fuel cells (FAFCs) exhibiting high power density and outstanding stability. However, the enhancement of the oxidation barrier is unavoidable in this alloy system owing to the electron transfer (ET) from B to Pd. In this study, a hydrogen doping strategy is employed to open charge freedom in PdB compounds and boost their formic acid oxidation reaction (FAOR) activity by suppressing the ET process. The resulting hydrogen-doped PdB (PdBH) exhibits an ultrahigh mass activity of up to 1.2A mg-1 Pd, which is 3.23 times that of the PdB catalyst and 9.55 times that of Pd black. Detailed experimental and theoretical studies show that the interstitial hydrogen leads to enhanced orbital hybridization and reduced electron density around Pd. This optimized ligand effect weakens the carbon monoxide adsorption and increases the direct pathway preference of PdBH, resulting in its outstanding catalytic activity for the FAOR. The development of this high-performance hydrogen-doped PdB catalyst is an important step toward the construction of advanced light element co-doped metal catalysts.

Enzymatic Mesoporous Metal Nanocavities for Concurrent Electrocatalysis of Nitrate to Ammonia Coupled with Polyethylene Terephthalate Upcycling

Electrochemical upcycling of waste pollutants into high value-added fuels and/or chemicals is recognized as a green and sustainable solution that can address the resource utilization on earth. Despite great efforts, their progress has seriously been hindered by the lack of high-performance electrocatalysts. In this work, bimetallic PdCu mesoporous nanocavities (MCs) are reported as a new bifunctional enzymatic electrocatalyst that realizes concurrent electrocatalytic upcycling of nitrate wastewater and polyethylene terephthalate (PET) plastic waste. Abundant metal mesopores and open nanocavities of PdCu MCs provide the enzymatic confinement of key intermediates for the deeper electroreduction of nitrate and accelerate the transport of reactants/products within/out of electrocatalyst, thus affording high ammonia Faradic efficiency (FENH3) of 96.6% and yield rate of 5.6 mg h-1 mg-1 at the cathode. Meanwhile, PdCu MC nanozymes trigger the selective electrooxidation of PET-derived ethylene glycol (EG) into glycolic acid (GA) and formic acid with high FEs of >90% by a facile regulation of potentials at the anode. Moreover, concurrent electrosynthesis of value-added NH3 and GA is disclosed in the two-electrode coupling system, further confirming the high efficiency of bifunctional PdCu MC nanozymes in producing value-added fuels and chemicals from waste pollutants in a sustainable manner.

Built-In Positive Valence Space Shifting the Chemical Equilibrium Forward for Nitrate Reduction to Ammonia

The electrochemical conversion of nitrate pollutants into value-added ammonia (NH3) is an appealing alternative synthetic route for sustainable NH3 production. However, the development of the electrocatalytic nitrate-to-ammonia reduction reaction (NO3RR) has been hampered by unruly reactants and products at the interface and the accompanied sluggish kinetic rate. In this work, a built-in positive valence space is successfully constructed over FeCu nanocrystals to rationally regulate interfacial component concentrations and positively shift the chemical equilibrium. With positive valence Cu optimizing the active surface, the space between the stern and shear layers becomes positive, which is able to continuously attract the negatively charged NO3- reactant and repulse the positively charged NH4+ product even under high current density, thus significantly boosting the NO3RR kinetics. The system with a built-in positive valence space affords an ampere-level NO3RR performance with the highest NH3 yield rate of 150.27 mg h-1 mg-1 at -1.3 V versus RHE with an outstanding NH3 current density of 189.53 mA cm-2, as well as a superior Faradaic efficiency (FE) of 97.26% at -1.2 V versus RHE. The strategy proposed here underscores the importance of interfacial concentration regulation and can find wider applicability in other electrochemical syntheses suffering from sluggish kinetics.

Three-Dimensional Porous Cu/Cu2+1O Nanosheet Arrays Promote Electrochemical Nitrate-to-Ammonia Conversion

The efficiency of electrochemical nitrate (NO3-) reduction to ammonia (NH3) still remains a challenge due to the sluggish kinetics of the complex eight-electron reduction process and competitive hydrogen evolution reaction (HER). Herein, we designed new three-dimensional (3D) porous Cu/Cu2+1O nanosheet arrays (Cu/Cu2+1O NSA) by coupling a template-directed method with in situ electroreduction. Thanks to the 3D porous structure and in-plane heterojunctions, Cu/Cu2+1O NSA can provide abundant active sites and a good interfacial effect, obtaining the maximum Faradaic efficiency (FE) of ammonia (88.09%) and high yield rate of 0.2634 mmol h-1 cm-2, which is higher than that of CuO nanosheets (77.81% and 0.2188 mmol h-1 cm-2) and CuO nanoparticles (34.60% and 0.0692 mmol h-1 cm-2). Experimental results and DFT simulations show that the interface effect of Cu/Cu2+1O can decrease the reaction energy barrier of the key step (*NO to *NOH) and can greatly inhibit the competitive hydrogen evolution reaction, thereby achieving excellent electrocatalytic performance for nitrate-to-ammonia conversion.

Metal Doped Unconventional Phase IrNi Nanobranches: Tunable Electrochemical Nitrate Reduction Performance and Pollutants Upcycling

Electrochemical nitrate reduction (NO3RR) provides a new option to abate nitrate contamination with a low carbon footprint. Restricted by competitive hydrogen evolution, achieving satisfied nitrate reduction performance in neutral media is still a challenge, especially for the regulation of this multielectron multiproton reaction. Herein, facile element doping is adopted to tune the catalytic behavior of IrNi alloy nanobranches with an unconventional hexagonal close-packed (hcp) phase toward NO3RR. In particular, the obtained hcp IrNiCu nanobranches favor the ammonia production and suppress byproduct formation in a neutral electrolyte indicated by in situ differential electrochemical mass spectrometry, with a high Faradaic efficiency (FE) of 85.6% and a large yield rate of 1253 μg cm-2 h-1 at -0.4 and -0.6 V (vs reversible hydrogen electrode (RHE)), respectively. In contrast, the resultant hcp IrNiCo nanobranches promote the formation of nitrite, with a peak FE of 33.1% at -0.1 V (vs RHE). Furthermore, a hybrid electrolysis cell consisting of NO3RR and formaldehyde oxidation is constructed, which are both catalyzed by hcp IrNiCu nanobranches. This electrolyzer exhibits lower overpotential and holds the potential to treat polluted air and wastewater simultaneously, shedding light on green chemical production based on contaminate degradation.

Enabling Logistics Automation in Nanofactory: Cobalt Phosphide Embedded Metal-Organic Frameworks for Efficient Electrocatalytic Nitrate Reduction to Ammonia

Electrocatalytic nitrate reduction reaction (NitRR) in neutral condition offers a promising strategy for green ammonia synthesis and wastewater treatment, the rational design of electrocatalysts is the cornerstone. Inspired by modern factory design where both machines and logistics matter for manufacturing, it is reported that cobalt phosphide (CoP) nanoparticles embedded in zinc-based zeolite imidazole frameworks (Zn-ZIF) function as a nanofactory with high performance. By selective phosphorization of ZnCo bimetallic zeolite imidazole framework (ZnCo-ZIF), the generated CoP nanoparticles act as "machines" (active sites) for molecular manufacturing (NO3 - to NH4 + conversion). The purposely retained framework (Zn-ZIFs) with positive charge promotes logistics automation, i.e., the automatic delivery of NO3 - reactants and timely discharge of NH4 + products in-and-out the nanofactory due to electrostatic interaction. Moreover, the interaction between Zn-ZIF and CoP modulates the Co sites into electron insufficient state with upshifted d-band center, facilitating the reduction/hydrogenation of NO3 - to ammonia and restricting the competitive hydrogen evolution. Consequently, the assembled CoP/Zn-ZIF nanofactory exhibits superior NitRR performances with a high Faraday efficiency of ≈97% and a high ammonia yield of 0.89 mmol cm-1 h-1 in neutral condition, among the best of reported electrocatalysts. The work provides new insights into the design principles of efficient NitRR electrocatalysts.

Lattice engineering of noble metal-based nanomaterials via metal-nonmetal interactions for catalytic applications

Noble metal-based nanomaterials possess outstanding catalytic properties in various chemical reactions. However, the increasing cost of noble metals severely hinders their large-scale applications. A cost-effective strategy is incorporating noble metals with light nonmetal elements (e.g., H, B, C, N, P and S) to form noble metal-based nanocompounds, which can not only reduce the noble metal content, but also promote their catalytic performances by tuning their crystal lattices and introducing additional active sites. In this review, we present a concise overview of the recent advancements in the preparation and application of various kinds of noble metal-light nonmetal binary nanocompounds. Besides introducing synthetic strategies, we focus on the effects of introducing light nonmetal elements on the lattice structures of noble metals and highlight notable progress in the lattice strain engineering of representative core-shell nanostructures derived from these nanocompounds. In the meantime, the catalytic applications of the light element-incorporated noble metal-based nanomaterials are discussed. Finally, we discuss current challenges and future perspectives in the development of noble metal-nonmetal based nanomaterials.

Sulphur-Boosted Active Hydrogen on Copper for Enhanced Electrocatalytic Nitrate-to-Ammonia Selectivity

Electrocatalytic nitrate reduction to ammonia is a promising approach in term of pollutant appreciation. Cu-based catalysts performs a leading-edge advantage for nitrate reduction due to its favorable adsorption with *NO3. However, the formation of active hydrogen (*H) on Cu surface is difficult and insufficient, leading to the significant generation of by-product NO2 -. Herein, sulphur doped Cu (Cu-S) is prepared via an electrochemical conversion strategy and used for nitrate electroreduction. The high Faradaic efficiency (FE) of ammonia (~98.3 %) and an extremely low FE of nitrite (~1.4 %) are achieved on Cu-S, obviously superior to its counterpart of Cu (FENH3: 70.4 %, FENO2 -: 18.8 %). Electrochemical in situ characterizations and theoretical calculations indicate that a small amount of S doping on Cu surface can promote the kinetics of H2O dissociation to active hydrogen. The optimized hydrogen affinity validly decreases the hydrogenation kinetic energy barrier of *NO2, leading to an enhanced NH3 selectivity.

Ir-Doped CuPd Single-Crystalline Mesoporous Nanotetrahedrons for Ethylene Glycol Oxidation Electrocatalysis: Enhanced Selective Cleavage of C-C Bond

The development of highly efficient electrocatalysts for complete oxidation of ethylene glycol (EG) in direct EG fuel cells is of decisive importance to hold higher energy efficiency. Despite some achievements, their progress, especially electrocatalytic selectivity to complete oxidated C1 products, is remarkably slower than expected. In this work, we developed a facile aqueous synthesis of Ir-doped CuPd single-crystalline mesoporous nanotetrahedrons (Ir-CuPd SMTs) as high-performance electrocatalyst for promoting oxidation cleavage of C-C bond in alkaline EG oxidation reaction (EGOR) electrocatalysis. The synthesis relied on precise reduction/co-nucleation and epitaxial growth of Ir, Cu and Pd precursors with cetyltrimethylammonium chloride as the mesopore-forming surfactant and extra Br- as the facet-selective agent under ambient conditions. The products featured concave nanotetrahedron morphology enclosed by well-defined (111) facets, single-crystalline and mesoporous structure radiated from the center, and uniform elemental composition without any phase separation. Ir-CuPd SMTs disclosed remarkably enhanced electrocatalytic activity and excellent stability as well as superior selectivity of C1 products for alkaline EGOR electrocatalysis. Detailed mechanism studies demonstrated that performance improvement came from structural and compositional synergies, which kinetically accelerated transports of electrons/reactants within active sites of penetrated mesopores and facilitated oxidation cleavage of high-energy-barrier C-C bond of EG for desired C1 products. More interestingly, Ir-CuPd SMTs performed well in coupled electrocatalysis of anode EGOR and cathode nitrate reduction, highlighting its high potential as bifunctional electrocatalyst in various applications.

Electrochemical Nitrate Reduction: Ammonia Synthesis and the Beyond

Natural nitrogen cycle has been severely disrupted by anthropogenic activities. The overuse of N-containing fertilizers induces the increase of nitrate level in surface and ground waters, and substantial emission of nitrogen oxides causes heavy air pollution. Nitrogen gas, as the main component of air, has been used for mass ammonia production for over a century, providing enough nutrition for agriculture to support world population increase. In the last decade, researchers have made great efforts to develop ammonia processes under ambient conditions to combat the intensive energy consumption and high carbon emission associated with the Haber-Bosch process. Among different techniques, electrochemical nitrate reduction reaction (NO3RR) can achieve nitrate removal and ammonia generation simultaneously using renewable electricity as the power, and there is an exponential growth of studies in this research direction. Here, a timely and comprehensive review on the important progresses of electrochemical NO3RR, covering the rational design of electrocatalysts, emerging CN coupling reactions, and advanced energy conversion and storage systems is provided. Moreover, future perspectives are proposed to accelerate the industrialized NH3 production and green synthesis of chemicals, leading to a sustainable nitrogen cycle via prosperous N-based electrochemistry.

Crystal Phase Engineering of Ultrathin Alloy Nanostructures for Highly Efficient Electroreduction of Nitrate to Ammonia

Electrocatalytic nitrate reduction reaction (NO3RR) toward ammonia synthesis is recognized as a sustainable strategy to balance the global nitrogen cycle. However, it still remains a great challenge to achieve highly efficient ammonia production due to the complex proton-coupled electron transfer process in NO3RR. Here, the controlled synthesis of RuMo alloy nanoflowers (NFs) with unconventional face-centered cubic (fcc) phase and hexagonal close-packed/fcc heterophase for highly efficient NO3RR is reported. Significantly, fcc RuMo NFs demonstrate high Faradaic efficiency of 95.2% and a large yield rate of 32.7 mg h-1 mgcat -1 toward ammonia production at 0 and -0.1 V (vs reversible hydrogen electrode), respectively. In situ characterizations and theoretical calculations have unraveled that fcc RuMo NFs possess the highest d-band center with superior electroactivity, which originates from the strong Ru─Mo interactions and the high intrinsic activity of the unconventional fcc phase. The optimal electronic structures of fcc RuMo NFs supply strong adsorption of key intermediates with suppression of the competitive hydrogen evolution, which further determines the remarkable NO3RR performance. The successful demonstration of high-performance zinc-nitrate batteries with fcc RuMo NFs suggests their substantial application potential in electrochemical energy supply systems.

Ambient Electrochemical Ammonia Synthesis: From Theoretical Guidance to Catalyst Design

Ammonia, a vital component in the synthesis of fertilizers, plastics, and explosives, is traditionally produced via the energy-intensive and environmentally detrimental Haber-Bosch process. Given its considerable energy consumption and significant greenhouse gas emissions, there is a growing shift toward electrocatalytic ammonia synthesis as an eco-friendly alternative. However, developing efficient electrocatalysts capable of achieving high selectivity, Faraday efficiency, and yield under ambient conditions remains a significant challenge. This review delves into the decades-long research into electrocatalytic ammonia synthesis, highlighting the evolution of fundamental principles, theoretical descriptors, and reaction mechanisms. An in-depth analysis of the nitrogen reduction reaction (NRR) and nitrate reduction reaction (NitRR) is provided, with a focus on their electrocatalysts. Additionally, the theories behind electrocatalyst design for ammonia synthesis are examined, including the Gibbs free energy approach, Sabatier principle, d-band center theory, and orbital spin states. The review culminates in a comprehensive overview of the current challenges and prospective future directions in electrocatalyst development for NRR and NitRR, paving the way for more sustainable methods of ammonia production.

Unveiling Cutting-Edge Developments in Electrocatalytic Nitrate-to-Ammonia Conversion

The excessive enrichment of nitrate in the environment can be converted into ammonia (NH3) through electrochemical processes, offering significant implications for modern agriculture and the potential to reduce the burden of the Haber-Bosch (HB) process while achieving environmentally friendly NH3 production. Emerging research on electrocatalytic nitrate reduction (eNitRR) to NH3 has gained considerable momentum in recent years for efficient NH3 synthesis. However, existing reviews on nitrate reduction have primarily focused on limited aspects, often lacking a comprehensive summary of catalysts, reaction systems, reaction mechanisms, and detection methods employed in nitrate reduction. This review aims to provide a timely and comprehensive analysis of the eNitRR field by integrating existing research progress and identifying current challenges. This review offers a comprehensive overview of the research progress achieved using various materials in electrochemical nitrate reduction, elucidates the underlying theoretical mechanism behind eNitRR, and discusses effective strategies based on numerous case studies to enhance the electrochemical reduction from NO3 - to NH3. Finally, this review discusses challenges and development prospects in the eNitRR field with an aim to guide design and development of large-scale sustainable nitrate reduction electrocatalysts.

Ammonia Synthesis via Electrocatalytic Nitrate Reduction Using NiCoO2 Nanoarrays on a Copper Foam

Ammonia (NH3) plays a vital role in industrial and agricultural development. The electrocatalytic nitrate reduction reaction (eNO3RR) is an effective method to produce NH3 under environmental conditions but also requires considerably active and selective electrocatalysts. Herein, a copper foam was used as a conductive substrate for the electrode materials. Specifically, a Co metal-organic framework (Co-MOF) was in situ grown on the copper foam, etched, and calcined to form NiCoO2@Cu nanosheets, which were used as cathode electrodes for the eNO3RR. In 0.1 M Na2SO4 with 0.1 M NaNO3 electrolyte, NiCoO2@Cu nanosheets realized an NH3 yield of 5940.73 μg h-1 cm-2 at -0.9 V vs reversible hydrogen electrode (RHE), with a Faradaic efficiency of 94.2% at -0.7 V vs RHE. After 33 h of the catalytic reaction, the selectivity of NH3-N increased to 99.7%. The excellent electrocatalytic performance of NiCoO2@Cu nanosheets was attributed to the apparent synergistic effect between the Ni atoms and the Co atoms of bimetallic materials. This study shows that the Ni doping of NiCoO2@Cu nanosheets effectively facilitated the adsorption of NO3- on NiCoO2@Cu, and it promoted the eNO3RR.

Approaches to Improving the Selectivity of Nanozymes

Nanozymes mimic enzymes and that includes their selectivity. To achieve selectivity, significant inspiration for nanoparticle design can come from the geometric and molecular features that make enzymes selective catalysts. The two central features enzymes use are control over the arrangement of atoms in the active site and the placing of the active site down a nanoconfined substrate channel. The implementation of enzyme-inspired features has already been shown to both improve activity and selectivity of nanoparticles for a variety of catalytic and sensing applications. The tuning and control of active sites on metal nanoparticle surfaces ranges from simply changing the composition of the surface metal to sophisticated approaches such as the immobilization of single atoms on a metal substrate. Molecular frameworks provide a powerful platform for the implementation of isolated and discrete active sites while unique diffusional environments further improve selectivity. The implementation of nanoconfined substrate channels around these highly controlled active sites offers further ability to control selectivity through altering the solution environment and transport of reactants and products. Implementing these strategies together offers a unique opportunity to improve nanozyme selectivity in both sensing and catalysis.

N and OH-Immobilized Cu3 Clusters In Situ Reconstructed from Single-Metal Sites for Efficient CO2 Electromethanation in Bicontinuous Mesochannels

Cu-based catalysts hold promise for electrifying CO2 to produce methane, an extensively used fuel. However, the activity and selectivity remain insufficient due to the lack of catalyst design principles to steer complex CO2 reduction pathways. Herein, we develop a concept to design carbon-supported Cu catalysts by regulating Cu active sites' atomic-scale structures and engineering the carbon support's mesoscale architecture. This aims to provide a favorable local reaction microenvironment for a selective CO2 reduction pathway to methane. In situ X-ray absorption and Raman spectroscopy analyses reveal the dynamic reconstruction of nitrogen and hydroxyl-immobilized Cu3 (N,OH-Cu3) clusters derived from atomically dispersed Cu-N3 sites under realistic CO2 reduction conditions. The N,OH-Cu3 sites possess moderate *CO adsorption affinity and a low barrier for *CO hydrogenation, enabling intrinsically selective CO2-to-CH4 reduction compared to the C-C coupling with a high energy barrier. Importantly, a block copolymer-derived carbon fiber support with interconnected mesopores is constructed. The unique long-range mesochannels offer an H2O-deficient microenvironment and prolong the transport path for the CO intermediate, which could suppress the hydrogen evolution reaction and favor deep CO2 reduction toward methane formation. Thus, the newly developed catalyst consisting of in situ constructed N,OH-Cu3 active sites embedded into bicontinuous carbon mesochannels achieved an unprecedented Faradaic efficiency of 74.2% for the CO2 reduction to methane at an industry-level current density of 300 mA cm-2. This work explores effective concepts for steering desirable reaction pathways in complex interfacial catalytic systems via modulating active site structures at the atomic level and engineering pore architectures of supports on the mesoscale to create favorable microenvironments.

Wireless Photoactivated Targeted Nanosystem for Oncotherapy Via Synergistic Effects of Hyperthermia/Redox Stress Amplification/GSK-3β Activity Inhibition

Highly soluble salts and gas mediated therapies are emerging antitumor strategies. However, the therapeutic efficacy remains restricted by difficulty in delivering them to the tumor site and poorly controlled release in deep tissues. Here, an intelligent wireless photoactivated targeted nanosystem is designed for delivering LiCl and H2 to tumors for therapy. LiCl causes cell death by inhibiting the activity of GSK-3β. H2 selectively interacts with reactive oxygen species in the tumor, leading to redox stress, which induces apoptosis. The significant heat generated by the nanosystem not only kills tumor cells but also accelerates the dissolution of LiCl and the release of H2. The rapid dissolution of LiCl leads to a surge in intracellular osmotic pressure, which further intensifies the redox stress response and enhances the efficiency of therapy. The nanosystem shows efficient tumor therapeutic capability via synergistic effects of hyperthermia/redox stress amplification/GSK-3β activity inhibition.

Bimetallic synergistic catalysts based on two-dimensional carbon-rich conjugated frameworks for nitrate electrocatalytic reduction to ammonia: catalyst screening and mechanism insights

The discovery of the 'two birds, one stone' electrochemical nitrate reduction reaction (NO3RR) allows for the removal of harmful NO3-pollutants as well as the production of economically beneficial ammonia (NH3). However, current understanding of the catalytic mechanism of NO3RR is not enough, and this research is still challenging. To determine the mechanism needed to create efficient electrocatalysts, we thoroughly examined the catalytic activity of molybdenum-based diatomic catalysts (DACs) anchored on two-dimensional carbon-rich conjugated frameworks (2D CCFs) for NO3RR. Among the 23 candidate materials, after a four-step screening method and detailed mechanism studies, we discovered that NO3RR can efficiently generate NH3by following the N-end pathway on the MoTi-Pc, MoMn-Pc, and MoNb-Pc, with limiting potential of -0.33 V, -0.13 V, and -0.38 V, respectively. The activity of NO3RR can be attributed to the synergistic effect of the TM1-TM2dimer d orbital coupling to the anti-bonding orbital of NO3-. Additionally, high hybridization between the Mo-4d, TM-3d(4d), and NO3--2p orbitals on the MoTMs-Pc DACs can speed up the flow of electrons from the Mo-TM dual-site to NO3-. The research presented here paves the way for the reasonable design of effective NO3RR catalysts and offers a theoretical basis for experimental research.

Modulating the Active Hydrogen Adsorption on Fe─N Interface for Boosted Electrocatalytic Nitrate Reduction with Ultra-Long Stability

The electrocatalytic reduction of nitrate (NO3 - ) to nitrogen (N2 ) is an environmentally friendly approach for efficient N-cycle management (toward a nitrogen-neutral cycle). However, poor catalyst durability and the competitive hydrogen evolution reaction significantly impede its practical application. Interface-chemistry engineering, utilizing the close relationship between the catalyst surface/interface microenvironment and electron/proton transfer process, has facilitated the development of catalysts with high intrinsic activity and physicochemical durability. This study reports the synthesis of a nitrogen-doped carbon-coated rice-like iron nitride (RL-Fe2 N@NC) electrocatalyst with excellent electrocatalytic nitrate-reduction reaction activity (high N2 selectivity (≈96%) and NO3 - conversion (≈86%)). According to detailed mechanistic investigations by in situ tests and theoretical calculations, the strong hydrogenation ability of iron nitride and enhanced nitrate enrichment of the system synergistically contribute to the rapid hydrogenation of nitrogen-containing species, increasing the intrinsic activity of the catalyst and reducing the occurrence of the competing hydrogen-evolution side reaction. Moreover, RL-Fe2 N@NC shows excellent stability, retaining good NO3 - -to-N2 electrocatalysis activity for more than 40 cycles (one cycle per day). This paper could guide the interfacial design of Fe-based composite nanostructures for electrocatalytic nitrate reduction, facilitating a shift toward nitrogen neutrality.

A Bi-Co Corridor Construction Effectively Improving the Selectivity of Electrocatalytic Nitrate Reduction toward Ammonia by Nearly 100

Improving the selective ammonia production capacity of electrocatalytic nitrate reduction reaction (NO3 RR) at ambient conditions is critical to the future development and industrial application of electrosynthesis of ammonia. However, the reaction involves multi-proton and electron transfer as well as the desorption and underutilization of intermediates, posing a challenge to the selectivity of NO3 RR. Here the electrodeposition site of Co is modulated by depositing Bi at the bottom of the catalyst, thus obtaining the Co+Bi@Cu NW catalyst with a Bi-Co corridor structure. In 50 mm NO3 - , Co+Bi@Cu NW exhibits a highest Faraday efficiency of ≈100% (99.51%), an ammonia yield rate of 1858.2 µg h-1  cm-2 and high repeatability at -0.6 V versus the reversible hydrogen electrode. Moreover, the change of NO2 - concentration on the catalyst surface observed by in situ reflection absorption imaging and the intermediates of the NO3 RR process detected by electrochemical in situ Raman spectroscopy together verify the NO2 - trapping effect of the Bi-Co corridor structure. It is believed that the measure of modulating the deposition site of Co by loading Bi element is an easy-to-implement general method for improving the selectivity of NH3 production as well as the corresponding scientific research and applications.

Liposome-Templated Green Synthesis of Mesoporous Metal Nanostructures with Universal Composition for Biomedical Application

Porous noble metal nanoparticles have received particular attention recently for their unique optical, thermal, and catalytic functions in biomedicine. However, limited progress has been made to synthesize such porous metallic nanostructures with large mesopores (≥25 nm). Here, a green yet facile synthesis strategy using biocompatible liposomes as templates to mediate the formation of mesoporous metallic nanostructures in a controllable fashion is reported. Various monodispersed nanostructures with well-defined mesoporous shape and large mesopores (≈ 40 nm) are successfully synthesized from mono- (Au, Pd, and Pt), bi- (AuPd, AuPt, AuRh, PtRh, and PdPt), and tri-noble metals (AuPdRh, AuPtRh, and AuPdPt). Along with a successful demonstration of its effectiveness in synthesis of various mesoporous nanostructures, the possible mechanism of liposome-guided formation of such nanostructures via time sectioning of the synthesis process (monitoring time-resolved growth of mesoporous structures) and computational quantum molecular modeling (analyzing chemical interaction energy between metallic cations and liposomes at the enthalpy level) is also revealed. These mesoporous metallic nanostructures exhibit a strong photothermal effect in the near-infrared region, effective catalytic activities in hydrogen peroxide decomposition reaction, and high drug loading capacity. Thus, the liposome-templated method provides an inspiring and robust avenue to synthesize mesoporous noble metal-based nanostructures for versatile biomedical applications.

Modulating Metal-Nitrogen Coupling in Anti-Perovskite Nitride via Cation Doping for Efficient Reduction of Nitrate to Ammonia

The complexes of metal center and nitrogen ligands are the most representative systems for catalyzing hydrogenation reactions in small molecule conversion. Developing heterogeneous catalysts with similar active metal-nitrogen functional centers, nevertheless, still remains challenging. In this work, we demonstrate that the metal-nitrogen coupling in anti-perovskite Co4 N can be effective modulated by Cu doping to form Co3 CuN, leading to strongly promoted hydrogenation process during electrochemical reduction of nitrate (NO3 - RR) to ammonia. The combination of advanced spectroscopic techniques and density functional theory calculations reveal that Cu dopants strengthen the Co-N bond and upshifted the metal d-band towards the Fermi level, promoting the adsorption of NO3 - and *H and facilitating the transition from *NO2 /*NO to *NO2 H/*NOH. Consequently, the Co3 CuN delivers noticeably better NO3 - RR activity than the pristine Co4 N, with optimal Faradaic efficiency of 97 % and ammonia yield of 455.3 mmol h-1  cm-2 at -0.3 V vs. RHE. This work provides an effective strategy for developing high-performance heterogeneous catalyst for electrochemical synthesis.

Polyethylenimine-Ethylenediamine-Induced Pd Metallene toward Alkaline Oxygen Reduction

Designing two-dimensional (2D) materials functionalized with organic molecules is an effective tactic to enhance catalytic performances for the oxygen reduction reaction (ORR). Herein, we synthesize Pd metallene with in situ modification of polyethylenimine-ethylenediamine (Pd@PEI-EDA metallene), in which PEI-EDA serves as both the structure-directing agent and modifier. Pd@PEI-EDA metallene has ample active sites and tuneable electronic structures due to ultrathin nanosheets with abundant wrinkles and interfacial structure. In contrast with commercial Pd/C and Pt/C, Pd@PEI-EDA metallene displays preferable catalytic ORR performance under alkaline conditions. This work offers an in situ interface engineering tactic for the preparation of 2D polymer-metal electrocatalysts to boost the ORR performance.

Microenvironment Engineering to Promote Selective Ammonia Electrosynthesis from Nitrate over a PdCu Hollow Catalyst

The electrosynthesis of recyclable ammonia (NH₃ ) from nitrate under ambient conditions is of great importance but still full of challenges for practical application. Herein, an efficient catalyst design strategy is developed that can engineer the surface microenvironment of a PdCu hollow (PdCu-H) catalyst to confine the intermediates and thus promote selective NH₃ electrosynthesis from nitrate. The hollow nanoparticles are synthesized by in situ reduction and nucleation of PdCu nanocrystals along a self-assembled micelle of a well-designed surfactant. The PdCu-H catalyst shows a structure-dependent selectivity toward the NH₃ product during the nitrate reduction reaction (NO₃ ^- RR) electrocatalysis, enabling a high NH₃ Faradaic efficiency of 87.3% and a remarkable NH₃ yield rate of 0.551 mmol h^-1 mg^-1 at -0.30 V (vs reversible hydrogen electrode). Moreover, this PdCu-H catalyst delivers high electrochemical performance in the rechargeable zinc-NO₃ ^- battery. These results provide a promising design strategy to tune catalytic selectivity for efficient electrosynthesis of renewable NH₃ and feedstocks.

Defect engineering of two-dimensional materials for advanced energy conversion and storage

In the global trend towards carbon neutrality, sustainable energy conversion and storage technologies are of vital significance to tackle the energy crisis and climate change. However, traditional electrode materials gradually reach their property limits. Two-dimensional (2D) materials featuring large aspect ratios and tunable surface properties exhibit tremendous potential for improving the performance of energy conversion and storage devices. To rationally control the physical and chemical properties for specific applications, defect engineering of 2D materials has been investigated extensively, and is becoming a versatile strategy to promote the electrode reaction kinetics. Simultaneously, exploring the in-depth mechanisms underlying defect action in electrode reactions is crucial to provide profound insight into structure tailoring and property optimization. In this review, we highlight the cutting-edge advances in defect engineering in 2D materials as well as their considerable effects in energy-related applications. Moreover, the confronting challenges and promising directions are discussed for the development of advanced energy conversion and storage systems.