Rational design and synthesis of one-dimensional platinum-based nanostructures for oxygen-reduction electrocatalysis

Hydrogen Peroxide Spillover on Platinum-Iron Hybrid Electrocatalyst for Stable Oxygen Reduction

Iron-nitrogen-carbon (Fe-N-C) catalysts, although the most active platinum-free option for the cathodic oxygen reduction reaction (ORR), suffer from poor durability due to the Fe leaching and consequent Fenton effect, limiting their practical application in low-temperature fuel cells. This work demonstrates an integrated catalyst of a platinum-iron (PtFe) alloy planted in an Fe-N-C matrix (PtFe/Fe-N-C) to address this challenge. This novel catalyst exhibits both high-efficiency activity and stability, as evidenced by its impressive half-wave potential (E1/2) of 0.93 V versus reversible hydrogen electrode (vs RHE) and minimal 7 mV decay even after 50,000 potential cycles. Remarkably, it exhibits a very low hydrogen peroxide (H2O2) yield (0.07%) at 0.6 V and maintains this performance with negligible change after 10,000 potential cycles. Fuel cells assembled with this cathode PtFe/Fe-N-C catalyst show exceptional durability, with only 8 mV voltage loss at 0.8 A cm-2 after 30,000 cycles and ignorable current degradation at a voltage of 0.6 V over 85 h. Comprehensive in situ experiments and theoretical calculations reveal that oxygen species spillover from Fe-N-C to PtFe alloy not only inhibits H2O2 production but also eliminates harmful oxygenated radicals. This work paves the way for the design of highly efficient and stable ORR catalysts and has significant implications for the development of next-generation fuel cells.

Surface-structure tailoring of Dendritic PtCo nanowires for efficient oxygen reduction reaction

Platinum-based alloy nanowire catalysts demonstrates great promise as electrocatalysts to facilitate the cathodic oxygen reduction reaction (ORR) of proton exchange membrane fuel cells (PEMFCs). However, it is still challenge to further improve the Pt atom utilization of Pt based nanowires featuring inherent structural stability. Herein, a new structure of PtCo nanowire with nanodendrites was developed using CO-assistance solvent thermal method. The dendrite structure with an average length of about 7 nm are characterized by a Pt-rich surface and the high-index facets of {533}, {331} and {311}, and grows from the ultra-fine wire structure with an average diameter of about 3 nm. PtCo nanowires with nanodendrites developed in this work shows outstanding performance for ORR, in which its mass activity of 1.036 A/mgPt is 5.76 times, 1.74 times higher than that of commercial Pt/C (0.180 A/mgPt) and PtCo nanowires without nanodendrites (0.595 A/mgPt), and its mass activity loss is only 18% under the accelerated durability tests (ADTs) for 5k cycles. The significant improvement is attributed to high exposure of active sites induced by the dendrite structure with Pt-rich surface with the high-index facets and Pt-rich surface. This structure may provide a new idea for developing novel 1D Pt based electrocatalysts.

Rhombic dodecahedron nanoframes of PtIrCu with high-index faceted hyperbranched nanodendrites for efficient electrochemical ammonia oxidation via preferred NHx dimerization pathways

Ammonia has been emerging as a sustainable and environmentally friendly fuel. However, direct electrochemical ammonia oxidation reaction (AOR) in low-temperature fuel cells seriously suffers from high overpotential and deficient durability. Herein, rhombic dodecahedron nanoframe of platinum iridium copper (PtIrCu) with high-index faceted hyperbranched nanodendrites (RDNF-HNDs) was developed using a one-step self-etching solvothermal method. The framework structure with the high-index facets enables the PtIrCu nanocrystals to expose more effective active sites. They exhibit an ultra-low onset potential of 0.33 V vs. RHE and high mass activity of 26.1 A gPtIr-1 at 0.50 V, which is 140 mV lower and 7.5 times higher than that of commercial Pt/C in the AOR. In situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy verifies that AOR on PtIrCu RDNF-HNDs prefers to the NHx dimerization pathways, effectively alleviating the poison of Nads and NOx. The theoretical calculation also shows that both introducing Cu atoms into PtIr alloy and increasing the content of Ir in PtIrCu alloy can reduce the reaction energy barrier of electrochemical dehydrogenation from *NH2 to *NH. The specific structure of PtIrCu RDNF-NDs provides a new inspiration to solve the critical issue of electrocatalysts for AOR with low activity and durability.

Ni dispersed ultrathin carbon nanosheets as bi-functional oxygen electrocatalyst induced from graphite-like porous supramolecule

Excellent porosity and accessibility are key requirements during carbon-based materials design for energy conversion applications. Herein, a Ni-based porous supramolecular framework with graphite-like morphology (Ni-SOF) was rationally designed as a carbon precursor. Ultrathin carbon nanosheets dispersed with Ni nanoparticles and Ni-Nx sites (Ni@NiNx-N-C) were obtained via in-situ exfoliation during pyrolysis. Due to the hetero-porous structure succeeding from Ni-SOF, the Ni@NiNx-N-C catalyst showed outstanding bifunctional oxygen electrocatalytic activity with a narrow gap of 0.69 V between potential to deliver 10 mA cm-2 oxygen evolution and half-wave potential of oxygen reduction reaction, which even surpassed the Pt/C + IrO2 pair. Therefore, the corresponding zinc-air battery exhibited excellent power output and stability. The multiple Ni-based active sites, the unique 2D structure with a high graphitization degree and large specific surface area synergistically contributed to the excellent bifunctional electrocatalytic activity of Ni@NiNx-N-C. This work provided a novel viewpoint for the development of carbon-based electrocatalyst.

Advanced Catalyst Design and Reactor Configuration Upgrade in Electrochemical Carbon Dioxide Conversion

Electrochemical carbon dioxide reduction reaction (CO2 RR) driven by renewable energy shows great promise in mitigating and potentially reversing the devastating effects of anthropogenic climate change and environmental degradation. The simultaneous synthesis of energy-dense chemicals can meet global energy demand while decoupling emissions from economic growth. However, the development of CO2 RR technology faces challenges in catalyst discovery and device optimization that hinder their industrial implementation. In this contribution, a comprehensive overview of the current state of CO2 RR research is provided, starting with the background and motivation for this technology, followed by the fundamentals and evaluated metrics. Then the underlying design principles of electrocatalysts are discussed, emphasizing their structure-performance correlations and advanced electrochemical assembly cells that can increase CO2 RR selectivity and throughput. Finally, the review looks to the future and identifies opportunities for innovation in mechanism discovery, material screening strategies, and device assemblies to move toward a carbon-neutral society.

Spin state modulation on dual Fe center by adjacent Ni sites enabling the boosted activities and ultra-long stability in Zn-air batteries

Breakthrough in developing cost-effective Fe-based catalysts with superior oxygen reduction reaction (ORR) activities and ultra-long-term stability for application in Zn-air batteries (ZABs) remain a priority but still full of challenges. Herein, the neighboring NiN4 single-metal-atom and Fe2N5 dual-metal-atoms on the N-doped hollow carbon sphere (Fe/Ni-NHCS) were deliberately constructed as the efficient and robust ORR catalyst for ZABs. Both theory calculations and magnetic measurements demonstrate that the introduction of NiN4 provides a significant role on optimizing the electron spin state of Fe2N5 sites and reducing the energy barrier for the adsorption and conversion of the oxygen-containing intermediates, enabling the Fe/Ni-NHCS with excellent ORR performance and ultralow byproduct HO2- yield (0.5%). Impressively, the ZABs driven by Fe/Ni-NHCS exhibit unprecedented long-term rechargeable stability over 1200 h. This work paves a new venue to manipulate the spin state of active sites for simultaneously achieving superior catalytic activities and ultra-long-term stability in energy conversion technologies.

Abundant Exterior/Interior Active Sites Enable Three-Dimensional PdPtBiTe Dumbbells C-C Cleavage Electrocatalysts for Actual Alcohol Fuel Cells

Developing high-activity electrocatalysts is of great significance for the commercialization of direct alcohol fuel cells (DAFCs), but it still faces challenges. Herein, three-dimensional (3D) porous PdPtBiTe dumbbells (DBs) were successfully fabricated via the visible photoassisted method. The alloying effect, defect-rich surface/interface and nanoscale cavity, and open pores make the 3D PdPtBiTe DBs a comprehensive and remarkable electrocatalyst for the C1-C3 alcohol (ethanol, ethylene glycol, glycerol, and methanol) oxidation reaction (EOR, EGOR, GOR, and MOR, respectively) in an alkaline electrolyte, and the results of in situ Fourier transform infrared spectra revealed a superior C-C bond cleavage ability. The 3D PdPtBiTe DBs exhibit ultrahigh EOR, EGOR, GOR, and MOR mass activities of 25.4, 23.2, 16.8, and 18.3 A mgPd + Pt-1, respectively, considerably surpassing those of the commercial Pt/C and Pd/C. Moreover, the mass peak power densities of 3D PdPtBiTe DBs in actual ethanol, ethylene glycol, glycerol, or methanol fuel cells increase to 409.5, 501.5, 558.0, or 601.3 mW mgPd + Pt-1 in O2, respectively. This study provides a new class of multimetallic nanomaterials as state-of-the-art multifunctional anode electrocatalysts for actual DAFCs.

The synthesis of copper-modified biochar from Elsholtzia Harchowensis and its electrochemical activity towards the reduction of carbon dioxide

Phytoremediation techniques have been widely used in the treatment of heavy metal contaminated soils in recent years, but there is no effective post-treatment method for plant tissues containing heavy metals after remediation. Elsholtzia Harchowensis is a copper hyperaccumulator, commonly distributed in copper mining areas and often used for soil remediation of mine tailings. Moreover, copper-based catalysts are widely used in electrocatalytic reduction of carbon dioxide, which aims to convert carbon dioxide into useful fuels or chemicals. In this study, copper-modified biochar was prepared from Elsholtzia Harchowensis. Its specific surface area can reach as high as 1202.9 m2/g, with a certain porous structure and even distribution of copper on the amorphous carbon. Various products (such as carbon monoxide, methane, ethanol, and formic acid) could be obtained from the electrolytic reduction of carbon dioxide by using the as-prepared catalyst. Instantaneous current density of up to 15.3 mA/cm2 were achieved in 1.0 M KHCO3 solution at a potential of -0.82 V (vs. RHE). Electrolysis at a potential of -0.32 V (vs. RHE) for 8 h resulted in a stable current of about 0.25 mA/cm2, and the Faraday efficiency (FE) of carbon monoxide can reach as high as 74.6%. In addition, electrolysis at a potential of -0.52 V (vs. RHE) for 8 h led to a stable current of about 2.2 mA/cm2 and a FE of 8.7% for the C2 product. The rich variety of elements in plants leads to catalysts with complex structural and elemental characteristics as well, which facilitates the electrolytic reduction of carbon dioxide with a variety of useful products.

Recent advances in proton exchange membrane water electrolysis

Proton exchange membrane water electrolyzers (PEMWEs) are an attractive technology for renewable energy conversion and storage. By using green electricity generated from renewable sources like wind or solar, high-purity hydrogen gas can be produced in PEMWE systems, which can be used in fuel cells and other industrial sectors. To date, significant advances have been achieved in improving the efficiency of PEMWEs through the design of stack components; however, challenges remain for their large-scale and long-term application due to high cost and durability issues in acidic conditions. In this review, we examine the latest developments in engineering PEMWE systems and assess the gap that still needs to be filled for their practical applications. We provide a comprehensive summary of the reaction mechanisms, the correlation among structure-composition-performance, manufacturing methods, system design strategies, and operation protocols of advanced PEMWEs. We also highlight the discrepancies between the critical parameters required for practical PEMWEs and those reported in the literature. Finally, we propose the potential solution to bridge the gap and enable the appreciable applications of PEMWEs. This review may provide valuable insights for research communities and industry practitioners working in these fields and facilitate the development of more cost-effective and durable PEMWE systems for a sustainable energy future.

Ultrafast Microwave Synthesis of Ru-Doped MoP with Abundant P Vacancies as the Electrocatalyst for Hydrogen Generation in a Wide pH Range

Molybdenum phosphide (MoP) has received increasing attention for the hydrogen evolution reaction (HER) due to its Pt-like electronic structure and high electrical conductivity. In this work, a flake-like Ru-doped MoP with phosphorus vacancy (Ru-MoP-P_V) electrocatalyst is synthesized for the first time by a simple and rapid room-temperature microwave approach within 30 s. The created abundant phosphorus vacancies provide rich active sites and favor rapid electron transfer. The introduced Ru also enhances the catalytic activity of the synthesized electrocatalyst efficiently. Then, the designed Ru-MoP-P_V possesses low overpotentials for HER with 79, 100, and 161 mV in 1.0 M KOH, 0.5 M H₂SO₄, and 1.0 M phosphate-buffered saline to obtain 10 mA cm^-2. The Ru-MoP-P_V and NiFe-layered double hydroxide are used as the cathode and the anode, respectively, to drive water splitting and just need a low cell voltage of 1.6 V to achieve 10 mA cm^-2. This work provides a feasible way for the rapid production of metal phosphides for energy conversion and storage applications.

Lignin-derived iron carbide/Mn, N, S-codoped carbon nanotubes as a high-efficiency catalyst for synergistically enhanced oxygen reduction reaction and rechargeable zinc-air battery

Design of efficient and durable oxygen reduction reaction (ORR) electrocatalysts still remains challenge in sustainable energy storage and conversion devices. To achieve sustainable development, it is of importance to prepare high-quality carbon-derived ORR catalysts from biomass. Herein, Fe₅C₂ nanoparticles (NPs) were facilely entrapped in Mn, N, S-codoped carbon nanotubes (Fe₅C₂/Mn, N, S-CNTs) by a one-step pyrolysis of the mixed lignin, metal precursors and dicyandiamide. The resulting Fe₅C₂/Mn, N, S-CNTs had open and tubular structures, which exhibited positive shifts in the onset potential (E_onset = 1.04 V) and high half-wave potential (E_1/2 = 0.85 V), showing excellent ORR characteristics. Further, the typical catalyst-assembled Zn-air battery showed a high power density (153.19 mW cm^-2) and good cycling performance as well as obvious cost advantage. The research provides some valuable insights for rational construction of low-cost and environmentally sustainable ORR catalysts in clean energy field, coupled by offering some valuable insights for reusing biomass wastes.

In situ synthesis of two-dimensional graphene-like nickel-molybdenum nitride as efficient electrocatalyst towards water-splitting under large-current density

Transition metal nitride (TMNs) electrocatalysts have attracted tremendous attentions for their unique electron structure, high activity, and excellent stability. Herein, a two-dimensional (2D) graphene-like structured nickel-molybdenum nitride (Ni-MoN) on nickel foam (NF), is prepared via facile hydrothermal and following nitridation process. The as-prepared Ni-MoN-450 (pyrolysis at 450 °C) displays good hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performances in alkaline media. Only 22 mV and 117 mV are needed to achieve current densities of 10 mA cm^-2 and 500 mA cm^-2 in 1.0 M KOH, respectively, toward HER. The assembled two-electrode system, with the synthesized Ni-MoN-450 as the anode and cathode, exhibits good performance to achieve 1000 mA cm^-2 in 1.0 M KOH + 25 °C and 6.0 M KOH + 80 °C. Moreover, it also presents long-term stability under large-current density, which verified its robust property.

Coordination Engineering of Defective Cobalt-Nitrogen-Carbon Electrocatalysts with Graphene Quantum Dots for Boosting Oxygen Reduction Reaction

Developing efficient and robust metal-nitrogen-carbon electrocatalysts for oxygen reduction reaction (ORR) is of great significance for the application of hydrogen-oxygen fuel cells and metal-air batteries. Herein, a coordination engineering strategy is developed to improve the ORR kinetics and stability of cobalt-nitrogen-carbon (Co-N-C) electrocatalysts by grafting the oxygen-rich graphene quantum dots (GQDs) onto the zeolite imidazole frameworks (ZIFs) precursors. The optimized oxygen-rich GQDs-functionalized Co-N-C (G-CoNOC) electrocatalyst demonstrates an increased mass activity, nearly two times higher than that of pristine defective Co-N-C electrocatalyst, and retains a stability of 90.0% after 200 h, even superior to the commercial Pt/C. Comprehensive investigations demonstrate that the GQDs coordination can not only decrease carbon defects of Co-N-C electrocatalysts, improving the electron transfer efficiency and resistance to the destructive free radicals from H₂ O₂ , but also optimize the electronic structure of atomic Co active site to achieve a desired adsorption energy of OOH^- , leading to enhanced ORR kinetics and stability by promoting further H₂ O₂ reduction, as confirmed by theoretical calculations and experimental results. Such a coordination engineering strategy provides a new perspective for the development of highly active noble-metal-free electrocatalysts for ORR.

Cobalt Nanoparticles Anchored on N-Doped Porous Carbon Derived from Yeast for Enhanced Electrocatalytic Oxygen Reduction Reaction

Biomass-derived carbon materials have received extensive attention for use in high-performance electrocatalysts. In this study, a highly efficient electrocatalyst is developed with Co nanoparticles anchored on N-doped porous carbon material (CoNC) by using yeast as a biomass precursor through a facial activation and pyrolysis process. CoNC exhibits comparable catalytic activity with commercial 20 % Pt/C for the oxygen reduction reaction (ORR) with a half-wave potential of 0.854 V. A home-made primary Zn-air battery exhibited an open circuit potential of 1.45 V and a peak power density of 188 mW cm^-2 . Moreover, the discharge voltage of the primary battery maintained at a stable value up to 9 days. The enhanced performance of CoNC was probably ascribed to its high content of pyridinic-N and graphitic-N species, extra Co loading and porous structure, which provided sufficient active sites and channels to promote mass/electron transfer for ORR. This work provides a promising strategy to develop an efficient non-noble metal carbon-based electrocatalyst for fuel cells and metal-air batteries.

Regulating Reversible Oxygen Electrocatalysis by Built-in Electric Field of Heterojunction Electrocatalyst with Modified d-Band

Developing bifunctional catalysts for oxygen electrochemical reactions is essential for high-performance electrochemical energy devices. Here, a Mott-Schottky heterojunction composed of porous cobalt-nitrogen-carbon (Co-N-C) polyhedra containing abundant metal-phosphides for reversible oxygen electrocatalysis is reported. As a demonstration, this catalyst shows excellent activity in the oxygen electrocatalysis and thus delivers outstanding performance in rechargeable zinc-air batteries (ZABs). The built-in electric field in the Mott-Schottky heterojunction can promote electron transfer in oxygen electrocatalysis. More importantly, an appropriate d-band center of the heterojunction catalyst also endows oxygen intermediates with a balanced adsorption/desorption capability, thus enhancing oxygen electrocatalysis and consequently improving the performance of ZABs. The work demonstrates an important design principle for preparing efficient multifunctional catalysts in energy conversion technologies.

Deciphering the Superior Electronic Transmission Induced by the Li-N Ligand Pairs Boosted Photocatalytic Hydrogen Evolution

Atomic level decoration route is designated as one of the attractive methods to regulate both the charge density and band structure of photocatalysts. Moreover, to enable more efficient separation and transport of photocarriers, the construction of novel active sites can enhance both the reactivity and electrical conductivity of the crystal. Herein, an Li-N ligand is constructed via co-doping lithium and nitrogen atoms into ZnIn₂ S₄ lattice, which achieves a promoted photocatalytic H₂ evolution at 9737 µmol g^-1 h^-1 . The existence of Li-N ligand pairs and the behaviors of photocarriers on L₄₀ N₅ ZIS are determined systematically, which also provides a unique insight into the mechanism of the improved photocarrier migration rate. With the introduction of Li-N dual sites, the vacancy form of ZnIn₂ S₄ has changed and the photocatalytic stability is significantly improved. Interestingly, the change of charge density around Li-N ligand in ZnIn₂ S₄ is determined by theoretical simulations, as well as the regulated energy barrier of photocatalytic water splitting caused by Li-N dual sites, which act as both adsorption site for H₂ O and stronger reactive sites. This work helps to extend the understanding of ZnIn₂ S₄ and offers a fresh perspective for the creation of a Li-N co-doped photocatalyst.

Dynamic Reconstructed RuO2 /NiFeOOH with Coherent Interface for Efficient Seawater Oxidation

Developing efficient oxygen evolution reaction (OER) electrocatalysts for seawater electrolysis is still a big challenge. Herein, a facile one-pot approach is reported to synthesize RuO₂ -incorporated NiFe-metal organic framework (RuO₂ /NiFe-MOF) with unique nanobrick-nanosheet heterostructure as precatalyst. Driven by electric field, the RuO₂ /NiFe-MOF dynamically reconstructs into RuO₂ nanoparticles-anchored NiFe oxy/hydroxide nanosheets (RuO₂ /NiFeOOH) with coherent interface, during which the dissolution and redeposition of RuO₂ are witnessed. Owing to the synergistic interaction between RuO₂ and NiFeOOH, the as-reconstructed RuO₂ /NiFeOOH exhibits outstanding alkaline OER activity with an ultralow overpotential of 187.6 mV at 10 mA cm^-2 and a small Tafel slope of 31.9 mV dec^-1 and excellent durability at high current densities of 840 and 1040 mA cm^-2 in 1 m potassium hydroxide (KOH). When evaluated for seawater oxidation, the RuO₂ /NiFeOOH only needs a low overpotential of 326.2 mV to achieve 500 mA cm^-2 and can continuously catalyze OER at 500 mA cm^-2 for 100 h with negligible activity degradation. Density function theory calculations reveal that the presence of strong interaction and enhanced charge transfer along the coherent interface between RuO₂ and NiFeOOH ensures improved OER activity and stability.

Microwave Synthesis of Pt Clusters on Black TiO2 with Abundant Oxygen Vacancies for Efficient Acidic Electrocatalytic Hydrogen Evolution

Oxygen vacancies-enriched black TiO₂ is one promising support for enhancing hydrogen evolution reaction (HER). Herein, oxygen vacancies enriched black TiO₂ supported sub-nanometer Pt clusters (Pt/TiO₂ -O_V ) with metal support interactions is designed through solvent-free microwave and following low-temperature electroless approach for the first time. High-temperature and strong reductants are not required and then can avoid the aggregation of decorated Pt species. Experimental and theoretical calculation verify that the created oxygen vacancies and Pt clusters exhibit synergistic effects for optimizing the reaction kinetics. Based on it, Pt/TiO₂ -O_V presents remarkable electrocatalytic performance with 18 mV to achieve 10 mA cm^-2 coupled with small Tafel slope of 12 mV dec^-1 . This work provides quick synthetic strategy for preparing black titanium dioxide based nanomaterials.

Thermally constructed stable Zn-doped NiCoOx-z alloy structures on stainless steel mesh for efficient hydrogen production via overall hydrazine splitting in alkaline electrolyte

Hydrogen has a high energy density of approximately 120 to 140 MJ kg^-1, which is very high compared to other natural energy sources. However, hydrogen generation through electrocatalytic water splitting is a high electricity consumption process due to the sluggish oxygen evolution reaction (OER). As a result, hydrogen generation through hydrazine-assisted water electrolysis has recently been intensively investigated. The hydrazine electrolysis process requires a low potential compared to the water electrolysis process. Despite this, the utilization of direct hydrazine fuel cells (DHFCs) as portable or vehicle power sources necessitates the development of inexpensive and effective anodic hydrazine oxidation catalysts. Here, we prepared oxygen-deficient zinc-doped nickel cobalt oxide (Zn-NiCoO_x-z) alloy nanoarrays on stainless steel mesh (SSM) using a hydrothermal synthesis method followed by thermal treatment. Furthermore, the prepared thin films were used as electrocatalysts, and the OER and hydrazine oxidation reaction (HzOR) activities were investigated in three- and two-electrode systems. In a three-electrode system, Zn-NiCoO_x-z/SSM HzOR requires -0.116 V (vs RHE) potential to achieve a 50 mA cm^-2 current density, which is dramatically lower than the OER potential (1.493 V vs RHE). In a two-electrode system (Zn-NiCoO_x-z/SSM(-)∥Zn-NiCoO_x-z/SSM(+)), the overall hydrazine splitting potential (OHzS) required to reach 50 mA cm^-2 is only 0.700 V, which is dramatically less than the required potential for overall water splitting (OWS). These excellent HzOR results are due to the binder-free oxygen-deficient Zn-NiCoO_x-z/SSM alloy nanoarray, which provides a large number of active sites and improves the wettability of catalysts after Zn doping.

S-Species-Evoked High-Valence Ni2+ δ of the Evolved β-Ni(OH)2 Electrode for Selective Oxidation of 5-Hydroxymethylfurfural

An efficient NiS_x -modified β-Ni(OH)₂ electrode is reported for the selective oxidation reaction of 5-hydroxymethylfurfural (HMFOR) with excellent electrocatalytic 5-hydroxymethylfurfural (HMF) selectivity (99.4%), conversion (97.7%), and Faradaic efficiency (98.3%). The decoration of NiS_x will evoke high-valence Ni^{2+ δ} species in the reconstructed β-Ni(OH)₂ electrode, which are the real active species for HMFOR. The generated NiS_x /Ni(OH)O modulates the proton-coupled electron-transfer (PCET) process of HMFOR, where the electrocatalytically generated Ni(OH)O can effectively trap the protons from the CHO end in HMF to realize electron transfer. The oxygen evolution reaction (OER) competes with the HMFOR when NiS_x /Ni(OH)O continues to accumulate, to generate the NiS_x /NiO_x (OH)_y intermediate. Density functional theory (DFT) calculations and experimental results verify that the adsorption energy of HMF can be optimized through the increased NiS_x composition for more efficient capture of protons and electrons in the HMFOR.

Alumina supported copper oxide nanoparticles (CuO/Al2O3) as high-performance electrocatalysts for hydrazine oxidation reaction

Direct hydrazine liquid fuel cell (DHFC) is perceived as effectual energy generating mean owing to high conversion efficiency and energy density. However, the development of well-designed, cost effective and high performance electrocatalysts is the paramount to establish DHFCs as efficient energy generating technology. Herein, gamma alumina supported copper oxide nanocatalysts (CuO/Al₂O₃) are synthesized via impregnation method and investigated for their electrocatalytic potential towards hydrazine oxidation reaction. CuO with different weight percentages i.e., 4%, 8%, 12%, 16% and 20% are impregnated on gamma alumina support. X-ray diffraction analysis revealed the cubic crystal structure and nanosized particles of the prepared metal oxides. Transmission electron microscopy also referred to the cubic morphology and nanoparticle formation. Electrochemical oxidation potential of the CuO/Al₂O₃ nanoparticles is explored via cyclic voltammetry as the analytical tool. Optimization of conditions and electrocatalytic studies shown that 16% CuO/Al₂O₃ presented the best electronic properties towards N₂H₂ oxidation reaction. BET analysis ascertained the high surface area (131.2546 m² g¹) and large pore diameter (0.279605 cm³ g^-1) for 16% CuO/Al₂O₃. Nanoparticle formation, high porosity and enlarged surface area of the proposed catalysts resulted in significant oxidation current output (600 μA), high current density (8.2 mA cm^-2) and low charge transfer resistance (3.7 kΩ). Electrooxidation of hydrazine on such an affordable and novel electrocatalyst opens a gateway to further explore the metal oxide impregnated alumina materials for different electrochemical applications.

A New 2D Metal–Organic Framework for Photocatalytic Degradation of Organic Dyes in Water

Two–dimensional (2D) metal–organic frameworks (MOFs) are fascinating photocatalytic materials because of their unique physical and catalytic properties. Herein, we report a new (E)–4–(3–carboxyacrylamido) benzoic acid [ABA–MA] ligand synthesized under facile conditions. This ABA–MA ligand is further utilized to synthesize a copper-based 2D MOF via the solvothermal process. The resulting 2D MOF is characterized for morphology and electronic structural analysis using advanced techniques, such as proton nuclear magnetic resonance, Fourier-transform infrared spectroscopy, ultraviolet–visible spectroscopy, and scanning electron microscopy. Furthermore, 2D MOF is employed as a photocatalyst for degrading organic dyes, demonstrating the degradation/reduction of methylene blue (MeBl) dye with excellent catalytic/photodegradation activity in the absence of any photosensitizer or cocatalyst. The apparent rate constant (kap) values for the catalytic degradation/reduction of MeBl on the Cu(II)–[ABA-MA] MOF are reported to be 0.0093 min−1, 0.0187 min−1, and 0.2539 min−1 under different conditions of sunlight and NaBH4. The kinetics and stability evaluations reveal the noteworthy photocatalytic potential of the Cu(II)–[ABA–MA] MOF for wastewater treatment. This work offers new insights into the fabrication of new MOFs for highly versatile photocatalytic applications.

Magnetic Field-Assisted Construction and Enhancement of Electrocatalysts

Driven by the energy crisis and environmental pollution, developing sustainable clean energy is an effective strategy to realize carbon neutrality. Electrocatalytic reactions are crucial to sustainable energy conversion and storage technologies, and advanced electrocatalysts are required to improve the sluggish electrocatalytic reactions. The magnetic field, as a thermodynamic parameter independent of temperature and pressure, is vital in the construction of electrocatalysts and enhancement of electrocatalysis. In this Review, the recent progress of magnetic field-assisted construction of electrocatalysts and enhancement of electrocatalysis is comprehensively summarized. Originating from the structure-activity-performance relationship of electrocatalysts, the fundamentals of the magnetic field-induced construction of electrocatalysts, including the magnetocaloric effect, nucleation and growth, and phase regulation, have been illustrated. In addition, the magnetic effect on the electrocatalytic reaction, namely, the magnetothermal, magnetohydrodynamic and micro magnetohydrodynamic, Maxwell stress, Kelvin force, and spin selection effects, are discussed. Finally, the perspective and challenges for magnetic field-assisted construction of electrocatalysts and enhancement of electrocatalysis are proposed.

Pt-Based Oxygen Reduction Reaction Catalysts in Proton Exchange Membrane Fuel Cells: Controllable Preparation and Structural Design of Catalytic Layer

Proton exchange membrane fuel cells (PEMFCs) have attracted extensive attention because of their high efficiency, environmental friendliness, and lack of noise pollution. However, PEMFCs still face many difficulties in practical application, such as insufficient power density, high cost, and poor durability. The main reason for these difficulties is the slow oxygen reduction reaction (ORR) on the cathode due to the insufficient stability and catalytic activity of the catalyst. Therefore, it is very important to develop advanced platinum (Pt)-based catalysts to realize low Pt loads and long-term operation of membrane electrode assembly (MEA) modules to improve the performance of PEMFC. At present, the research on PEMFC has mainly been focused on two areas: Pt-based catalysts and the structural design of catalytic layers. This review focused on the latest research progress of the controllable preparation of Pt-based ORR catalysts and structural design of catalytic layers in PEMFC. Firstly, the design principle of advanced Pt-based catalysts was introduced. Secondly, the controllable preparation of catalyst structure, morphology, composition and support, and their influence on catalytic activity of ORR and overall performance of PEMFC, were discussed. Thirdly, the effects of optimizing the structure of the catalytic layer (CL) on the performance of MEA were analyzed. Finally, the challenges and prospects of Pt-based catalysts and catalytic layer design were discussed.

Electro-Synthesis of Organic Compounds with Heterogeneous Catalysis

Electro-organic synthesis has attracted a lot of attention in pharmaceutical science, medicinal chemistry, and future industrial applications in energy storage and conversion. To date, there has not been a detailed review on electro-organic synthesis with the strategy of heterogeneous catalysis. In this review, the most recent advances in synthesizing value-added chemicals by heterogeneous catalysis are summarized. An overview of electrocatalytic oxidation and reduction processes as well as paired electrocatalysis is provided, and the anodic oxidation of alcohols (monohydric and polyhydric), aldehydes, and amines are discussed. This review also provides in-depth insight into the cathodic reduction of carboxylates, carbon dioxide, CC, C≡C, and reductive coupling reactions. Moreover, the electrocatalytic paired electro-synthesis methods, including parallel paired, sequential divergent paired, and convergent paired electrolysis, are summarized. Additionally, the strategies developed to achieve high electrosynthesis efficiency and the associated challenges are also addressed. It is believed that electro-organic synthesis is a promising direction of organic electrochemistry, offering numerous opportunities to develop new organic reaction methods.

An integrated platinum-nanocarbon electrocatalyst for efficient oxygen reduction

Efficient and robust platinum-carbon electrocatalysts are of great significance for the long-term service of high-performance fuel cells. Here, we report a Pt alloy integrated in a cobalt-nitrogen-nanocarbon matrix by a multiscale design principle for efficient oxygen reduction reaction. This Pt integrated catalyst demonstrates an increased mass activity, 11.7 times higher than that of commercial Pt catalyst, and retains a stability of 98.7% after 30,000 potential cycles. Additionally, this integrated catalyst delivers a current density of 1.50 A cm⁻² at 0.6 V in the hydrogen-air fuel cell and achieves a power density of 980 mW cm⁻². Comprehensive investigations demonstrate that the synergistic contribution of components and structure in the platinum-carbon integrated catalyst is responsible for the high-efficiency ORR in fuel cells.

Improving fuel cell technologies based on Pt-based alloys is important for efficient fuel cells. Here, the authors report a hybrid PtCo alloy electrocatalyst for acidic oxygen reduction at high current densities and H₂/air fuel cell power densities.

Foamed Carbon-Supported Nickel-Iron Oxides Interspersed with Bamboo-Like Carbon Nanotubes for High-Performance Rechargeable Zinc-Air Batteries

The development of multi-component bi-functional electrocatalysts is necessary for commercialization of high-performance zinc-air batteries. Herein, foamed carbon-supported nickel-iron oxides interspersed with bamboo-like carbon nanotubes are prepared as bi-functional electrocatalysts for this battery type. During high temperature synthesis, edges of carbon sheets comprising the foamed carbon structure become involuted to form short carbon nanotubes. The composite of carbon nanotubes and network carbon confer high specific surface area and high electrical conductivity on the newly prepared materials. The supported NiFe₂ O₄ phase improves the oxygen reduction reaction (ORR) activity by fixing more N atoms, and high-valent Ni oxide (Ni₂ O₃ ) promotes the formation of OO bonds, which is conducive to the oxygen evolution reaction (OER). The optimized material exhibits excellent bi-functional electrocatalytic activity toward both ORR and OER, and its use in the assembled zinc-air battery cell results in a high power density of 150 mW cm^-2 with long discharge stability.

Ultrathin rhodium nanosheet-gold nanowire nanocomposites for alkaline methanol oxidation reaction

Electrostatically assembled ultrathin rhodium nanosheet-gold nanowire nanocomposites (Rh-Au CNSs) were used as an advanced electrocatalyst for the methanol oxidation reaction, which revealed a mass activity of 355 mA mg_Rh^-1 at 0.607 V potential, much higher than single metal Rh nanosheets (273 mA mg_Rh^-1) and commercial Rh nanoparticles (165 mA mg_Rh^-1).