Monodisperse Palladium Sulfide as Efficient Electrocatalyst for Oxygen Reduction Reaction

Phosphorus-Doping Enables the Superior Durability of a Palladium Electrocatalyst towards Alkaline Oxygen Reduction Reactions

The sluggish kinetics of oxygen reduction reactions (ORRs) require considerable Pd in the cathode, hindering the widespread of alkaline fuel cells (AFCs). By alloying Pd with transition metals, the oxygen reduction reaction's catalytic properties can be substantially enhanced. Nevertheless, the utilization of Pd-transition metal alloys in fuel cells is significantly constrained by their inadequate long-term durability due to the propensity of transition metals to leach. In this study, a nonmetallic doping strategy was devised and implemented to produce a Pd catalyst doped with P that exhibited exceptional durability towards ORRs. Pd3P0.95 with an average size of 6.41 nm was synthesized by the heat-treatment phosphorization of Pd nanoparticles followed by acid etching. After P-doping, the size of the Pd nanoparticles increased from 5.37 nm to 6.41 nm, and the initial mass activity (MA) of Pd3P0.95/NC reached 0.175 A mgPd-1 at 0.9 V, slightly lower than that of Pd/C. However, after 40,000 cycles of accelerated durability testing, instead of decreasing, the MA of Pd3P0.95/NC increased by 6.3% while the MA loss of Pd/C was 38.3%. The durability was primarily ascribed to the electronic structure effect and the aggregation resistance of the Pd nanoparticles. This research also establishes a foundation for the development of Pd-based ORR catalysts and offers a direction for the future advancement of catalysts designed for practical applications in AFCs.

Cyanogel-Induced Facile Synthesis of Palladium Hydride for Electrocatalytic Oxygen Reduction

Palladium hydride (PdHx) is one of the well-known electrocatalytic materials, yet its synthesis is still a challenge through an energy-efficient and straightforward method. Herein, we propose a new and facile cyanogel-assisted synthesis strategy for the preparation of PdH0.649 at a mild environment with NaBH4 as the hydrogen source. Unlike traditional inorganic Pd precursors, the unique Pd-CN-Pd bridge in Pdx[Pd(CN)4]y ⋅ aH2O cyanogel offers more favourable spatial sites for insertion of H atoms. The characteristic three-dimensional backbone of cyanogel also acts as a support scaffold resulting in the interconnected network structure of PdH0.649. Due to the incorporation of H atoms and interconnected network structure, the PdH0.649 achieves a high half-wave potential of 0.932 V, a high onset potential of 1.062 V, and a low activation energy, as well as a long-term lifetime for oxygen reduction reaction. Theoretical calculation demonstrates a downshift of the d-band centre of Pd in PdH0.649 owing to the dominant Pd-H incorporation that weakens the binding energies of the *OH intermediate species. Zn-air batteries (ZAB) based on PdH0.649 exhibits high power density, competitive open circuit voltage, and good stability, exceeding that of commercial Pt black. This work not only opens up a new avenue for the development of high-efficiency Pt-free catalysts but also provides an original approach and insight into the synthesis of PdHx.

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.

Pd "Kills Two Birds with One Stone" for the Synthesis of Catalyst: Dual Active Sites of Pd Triggers the Kinetics of O2 Electrocatalysis

Noble metal-based catalyst, despite their exorbitant cost, are the only successful catalyst for bifunctional oxygen electrocatalysis owing to their capability to drive forward the reaction rate kinetically. Therefore, it is desirable to diminish the noble metal loading without any compromise in the catalyst performance. In this study, the aim to achieve two goals with one action via a single-step route to have ultra-low loading of Pd in the catalyst. The Pd is used as a catalyst for C─C bond formation followed by complexation reactions or vice versa, in conventional Suzuki-Miyaura cross-coupling (SMCC) reaction, which yields a Pd-based porous organic polymer. Interestingly, it is found that dispersed Pd nanocluster (PdNC ) is present together with Pd single atom doped into nanocarbon (Pd-NC) matrix in the catalyst (PdNC /Pd-NC800 ) that obtained after pyrolysis of the porous polymer. The catalyst exhibits remarkable bifunctional activity and durability towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Further, it is studied that the in situ attenuated total reflection infrared (ATR-IR) spectroscopy at different electrochemical potentials during ORR and OER to observe the reaction intermediates. The homemade zinc-air battery with the catalyst displayed great performance, establishing the significance of PdNC /Pd-NC800 as a bifunctional oxygen electrocatalyst.

Reduced Tiara-like Palladium Complex for Suzuki Cross-Coupling Reactions

The design of highly active and structurally well-defined catalysts has become a crucial issue for heterogeneous catalysed reactions while reducing the amount of catalyst employed. Beside conventional synthetic routes, the employment of polynuclear transition metal complexes as catalysts or catalyst precursors has progressively intercepted a growing interest. These well-defined species promise to deliver catalytic systems where a strict control on the nuclearity allows to improve the catalytic performance while reducing the active phase loading. This study describes the development of a highly active and reusable palladium-based catalyst on alumina (Pd8 /Al2 O3 ) for Suzuki cross-coupling reactions. An octanuclear tiara-like palladium complex was selected as active phase precursor to give isolated Pd-clusters of ca. 1 nm in size on Al2 O3 . The catalyst was thoroughly characterised by several complementary techniques to assess its structural and chemical nature. The high specific activity of the catalyst has allowed to carry out the cross-coupling reaction in 30 min using only 0.12 mol % of Pd loading under very mild and green reaction conditions. Screening of various substrates and selectivity tests, combined with recycling and benchmarking experiments, have been used to highlight the great potentialities of this new Pd8 /Al2 O3 catalyst.

Versatile synthesis of nano-icosapods via cation exchange for effective photocatalytic conversion of biomass-relevant alcohols

Branched metal chalcogenide nanostructures with well-defined composition and configuration are appealing photocatalysts for solar-driven organic transformations. However, precise design and controlled synthesis of such nanostructures still remain a great challenge. Herein, we report the construction of a variety of highly symmetrical metal sulfides and heterostructured icosapods based on them, in which twenty branches were radially grown in spatially ordered arrangement, with a high degree of structure homogeneity. Impressively, the as-obtained CdS-PdxS icosapods manifest a significantly improved photocatalytic activity for the selective oxidation of biomass-relevant alcohols into corresponding aldehydes coupled with H2 evolution under visible-light irradiation (>420 nm), and the apparent quantum yield of the benzyl alcohol reforming can be achieved as high as 31.4% at 420 nm. The photoreforming process over the CdS-PdxS icosapods is found to be directly triggered by the photogenerated electrons and holes without participation of radicals. The enhanced photocatalytic performance is attributed to the fast charge separation and abundant active sites originating from the well-defined configuration and spatial organization of the components in the branched heterostructures.

Interfacial engineering of hydrophobic octadecanethiol/Pd metallene toward electrocatalytic nitrogen reduction

In this work, we propose the modification of ultrathin and wrinkled Pd metallene by hydrophobic octadecanethiol (Pdene@C18) via Pd-S bonds for the nitrogen reduction reaction. The hydrophobic self-assembled monolayer C18 can effectively capture more N₂ and inhibit the hydrogen evolution reaction. As a result, a high NH₃ yield and Faraday efficiency of 27.97 μg h^-1 mg_cat.^-1 and 14.29% are achieved for Pdene@C18 under neutral conditions, respectively, highlighting the modification of hydrophobic monolayers for efficient nitrogen electro-reduction to ammonia.

Centimeter-Scale PdS2 Ultrathin Films with High Mobility and Broadband Photoresponse

2D materials with mixed crystal phase will lead to the nonuniformity of performance and go against the practical application. Therefore, it is of great significance to develop a valid method to synthesize 2D materials with typical stoichiometry. Here, 2D palladium sulfides with centimeter scale and uniform stoichiometric ratio are synthesized via controlling the sulfurization temperature of palladium thin films. The relationship between sulfurization temperature and products is investigated in depth. Besides, the high-quality 2D PdS₂ films are synthesized via sulfurization at the temperature of 450-550 °C, which would be compatible with back-end-of-line processes in semiconductor industry with considering of process temperature. The PdS₂ films show an n-type semiconducting behavior with high mobility of 10.4 cm² V^-1 s^-1 . The PdS₂ photodetector presents a broadband photoresponse from 450 to 1550 nm. These findings provide a reliable way to synthesizing high-quality and large-area 2D materials with uniform crystal phase. The result suggests that 2D PdS₂ has significant potential in future nanoelectronics and optoelectronic applications.

Sulfur-Induced Low Crystallization of Ultrathin Pd Nanosheet Arrays for Sulfur Ion Degradation-Assisted Energy-Efficient H2 Production

The utilization of thermodynamically favorable sulfur oxidation reaction (SOR) as an alternative to sluggish oxygen evolution reaction is a promising technology for low-energy H₂ production while degrading the sulfur source from wastewater. Herein, amorphous/crystalline S-doped Pd nanosheet arrays on nickel foam (a/c S-Pd NSA/NF) is prepared by S-doping crystalline Pd NSA/NF.  Owing to the ultrathin amorphous nanosheet structure and the incorporation of S atoms, the a/c S-Pd NSA/NF provides a large number of active sitesand the optimized electronic structure, while exhibiting outstanding electrocatalytic activity in hydrogen evolution reaction (HER) and SOR. Therefore, the coupling system consisting of SOR-assisted HER can reach a current density of 100 mA cm^-2 at 0.642 V lower than conventional electrolytic water by 1.257 V, greatly reducing energy consumption. In addition, a/c S-Pd NSA/NF can generate H₂ over a long period of time while degrading S^2- in water to the value-added sulfur powder, thus further reducing the cost of H₂ production. This work proposes an attractive strategy for the construction of an advanced electrocatalyst for H₂ production and utilization of toxic sulfide wastewater by combining S-doping induced partial amorphization and ultrathin metal nanosheet arrays.

B, P-co-doped PdCu nanothorn assemblies for enhanced oxygen reduction electrolysis

Nonmetal doping is a promising strategy to improve electrocatalytic performance of noble metal based catalysts for oxygen reduction reaction (ORR). Herein, we report a facile method to fabricate PdCuBP nanothorn assemblies (PdCuBP NTAs) by co-doping B and P into pre-synthesized PdCu NTAs using NaBH₄and NaH₂PO₂as B source and P source, respectively. The metal-nonmetal structure and multi-branched morphology can optimize oxygen adsorption energy and avoid catalyst migration, agglomeration and Ostwald ripening. As such, the obtained PdCuBP NTAs exhibit efficient activity and excellent long-term stability for ORR. This research offers an excellent strategy for co-doping nonmetal elements into metal nanocrystals with controllable composition and structure to improve electrocatalytic ORR performance.

Electron delocalization triggers nonradical Fenton-like catalysis over spinel oxides

Nonradical Fenton-like catalysis offers opportunities to overcome the low efficiency and secondary pollution limitations of existing advanced oxidation decontamination technologies, but realizing this on transition metal spinel oxide catalysts remains challenging due to insufficient understanding of their catalytic mechanisms. Here, we explore the origins of catalytic selectivity of Fe-Mn spinel oxide and identify electron delocalization of the surface metal active site as the key driver of its nonradical catalysis. Through fine-tuning the crystal geometry to trigger Fe-Mn superexchange interaction at the spinel octahedra, ZnFeMnO₄ with high-degree electron delocalization of the Mn-O unit was created to enable near 100% nonradical activation of peroxymonosulfate (PMS) at unprecedented utilization efficiency. The resulting surface-bound PMS* complex can efficiently oxidize electron-rich pollutants with extraordinary degradation activity, selectivity, and good environmental robustness to favor water decontamination applications. Our work provides a molecule-level understanding of the catalytic selectivity and bimetallic interactions of Fe-Mn spinel oxides, which may guide the design of low-cost spinel oxides for more selective and efficient decontamination applications.

Emerging interstitial/substitutional modification of Pd-based nanomaterials with nonmetallic elements for electrocatalytic applications

Palladium (Pd)-based nanomaterials have been identified as potential candidates for various types of electrocatalytic reaction, but most of them typically exhibit unsatisfactory performances. Recently, extensive theoretical and experimental studies have demonstrated that the interstitial/substitutional modification of Pd-based nanomaterials with nonmetallic atoms (H, B, C, N, P, S) has a significant impact on their electronic structure and thus leads to the rapid development of one kind of promising catalyst for various electrochemical reactions. Considering the remarkable progress in this area, we highlight the most recent progress regarding the innovative synthesis and advanced characterization methods of nonmetallic atom-doped Pd-based nanomaterials and provide insights into their electrochemical applications. What's more, the unique structure- and component-dependent electrochemical performance and the underlying mechanisms are also discussed. Furthermore, a brief conclusion about the recent progress achieved in this field as well as future perspectives and challenges are provided.

Boosting the anti-poisoning ability of palladium towards electrocatalytic formic acid oxidation via polyphosphide chemistry

In this work, we reported a novel polyphosphide strategy for the synthesis of phosphorus doped Pd (P-Pd) using red phosphorus as the starting material at quasi-ambient conditions. Polyphophide anions, as the key reaction intermediates, served as the reducing agent and phosphorus source to modulate the surface electronic structure of Pd. The P-Pd obtained exhibited topmost CO tolerance and electrocatalytic activity to formic acid oxidation among the state-of-arts reports. The mass activity and turnover frequency of P-Pd reached 4413 mA mg^-1_Pd and 16.04 s^-1 at 0.8 V, which were 23.7 and 6.4 times that of commercial Pd/C respectively. After 1000 repeated cycles, 82% initial activity was reserved. Combined with the electrochemical analysis and the density functional theory calculation, the boosted electrochemical performances can be attributed to the size and electronic effects induced by the P doping, which increase the surface actives sites, inhibit the adsorption of CO and change the reaction pathway to favorable CO₂ route. A full cell was also assembled to demonstrate the practical potential of the P-Pd, which showed a maximum power density of 21.56 mW cm^-2. This polyphophide-based reaction route provides a new strategy for the preparation of efficient and durable phosphorus doped alloys for electrocatalysis.

Reusing Sulfur-Poisoned Palladium Waste as a Highly Active, Nonradical Fenton-like Catalyst for Selective Degradation of Phenolic Pollutants

Recycling of deactivated palladium (Pd)-based catalysts can not only lower the economic cost of their industrial use but also save the cost for waste disposal. Considering that the sulfur-poisoned Pd (Pd_xS_y) with a strong Pd-S bond is difficult to regenerate, here, we propose a direct reuse of such waste materials as an efficient catalyst for decontamination via Fenton-like processes. Among the Pd_xS_y materials with different poisoning degrees, Pd₄S stood out as the most active catalyst for peroxymonosulfate activation, exhibiting pollutant-degradation performance rivaling the Pd and Co²⁺ benchmarks. Moreover, the incorporated S atom was found to tune the surface electrostatic potentials and charge densities of the Pd active site, triggering a shift in catalytic pathway from surface-bound radicals to predominantly direct electron transfer pathway that favors a highly selective oxidation of phenols. The catalyst stability was also improved due to the formation of strong Pd-S bond that reduces corrosion. Our work paves a new way for upcycling of Pd-based industrial wastes and for guiding the development of advanced oxidation technologies toward higher sustainability.

Phase-Controlled Synthesis of Pd-Se Nanocrystals for Phase-Dependent Oxygen Reduction Catalysis

Searching for highly efficient oxygen reduction reaction (ORR) electrocatalysts for fuel cell technology, in which the crystal structure plays a powerful role in regulating the electrocatalysis, is urgent yet challenging. Herein, we have explored the active and stable Pd-Se alloy electrocatalysts with controlled phase toward alkaline ORR. The phase-controlled Pd-Se nanoparticles (NPs) show interesting phase-dependent electrocatalytic performance, in which the Pd₁₇Se₁₅ NPs/C exhibits much better ORR performance than its counterpart, Pd₇Se₄ NPs/C, and the commercial Pd/C and Pt/C. Based on the detailed analysis, Pd in Pd₁₇Se₁₅ possesses more Se atom coordination and a higher valence state, thus providing a stronger capacity for the absorption of oxygenated species. DFT further reveals more charge transfer from the Pd₁₇Se₁₅ surface to the *OOH intermediate, which is the reason for the activity enhancement.

Hydrogen Evolution and Oxygen Reduction Reactions in Acidic Media Catalyzed by Pd4 S Decorated N/S Doped Carbon Derived from Pd Coordination Polymer

The template-free synthesis and the characterization of an active electrocatalyst are performed for both the hydrogen evolution and oxygen reduction reactions in acidic media. In this work, the unique chelation mode of benzene-1,4-dithiocarboxamide (BDCA) is first used to synthesize a novel palladium-BDCA coordination polymer (PdBDCA) as a precursor of palladium sulfide nanoparticles-decorated nitrogen and sulfur doped carbon (Pd₄ S-SNC). The newly synthesized PdBDCA and Pd₄ S-SNC nanoparticles are characterized using chemical, electrochemical, and surface analysis methods. Notably, the nanoparticles obtained at 700 °C exhibit the remarkable catalytic property for the hydrogen evolution reaction in 0.5 m H₂ SO₄ , showing the overpotential of 32 mV (vs reversible hydrogen electrode (RHE)) and Tafel slope of 52 mV dec^-1 , which are comparable to that of Pt/C. The catalyst also shows a high oxygen reduction activity, offering the half-wave and onset potentials of 0.92 and 0.77 V (vs RHE) in 0.5 m H₂ SO₄ , with improved methanol tolerance and long-term stability compared with Pt/C. The present study gives a way for the design of excellent electrocatalyst for the energy conversion devices in the corrosive acidic environment.

Pd Nanocluster/Monolayer MoS2 Heterojunctions for Light-Induced Room-Temperature Hydrogen Sensing

Developing sensing approaches that can exploit visible light for the detection of low-concentration hydrogen at room temperatures has become increasingly important for the safe use of hydrogen in many applications. In this study, heterostructures composed of monolayer MoS₂ and Pd nanoclusters (Pd/MoS₂) acting as photo- and hydrogen-sensitizers are successfully fabricated in a facile and scalable manner. The uniform deposition of morphologically isotropic Pd nanoclusters (11.5 ± 2.2 nm) on monolayer MoS₂ produces a plethora of active heterojunctions, effectively suppressing charge carrier recombination under light illumination. The dual photo- and hydrogen-sensitizing functionality of Pd/MoS₂ can enable its use as an active sensing layer in optoelectronic hydrogen sensors. Gas-sensing examinations reveal that the sensing performance of Pd/MoS₂ is enhanced three-fold under visible light illumination (17% for 140 ppm of H₂) in comparison with dark light (5% for 140 ppm of H₂). Photoactivation is also found to enable excellent sensing reversibility and reproducibility in the obtained sensor. As a proof-of-concept, the integration of Pd nanoclusters and monolayer MoS₂ can open a new avenue for light-induced hydrogen gas sensing at room temperature.

Sulfurization-induced partially amorphous palladium sulfide nanosheets for highly efficient electrochemical hydrogen evolution

Partially amorphous PdS was synthesized by sulfurizing crystalline palladium nanosheets via a facile method, displaying excellent activity and stability towards hydrogen evolution in alkaline media.

B-Doped PdRu nanopillar assemblies for enhanced formic acid oxidation electrocatalysis

Adjusting the morphology and composition of Pd-based materials is a promising strategy to improve their performance for the electrocatalytic formic acid oxidation reaction (FAOR). In this work, we report the preparation of B-doped PdRu nanopillar assemblies (B-PdRu NPAs) by a two-step method using NaBH4 as the boron dopant. On combining the hyper-branched structure and the multi-component synergistic effect, B-PdRu NPAs achieve a high mass activity of 1.09 mA μg-1Pd for the FAOR and retain 73.19% of the initial activity after 500 cycles, which is superior to undoped counterparts. The proposed synthesis strategy provides a simple method for the synthesis of metal-nonmetal nanomaterials with desired composition and design structure for electrocatalytic fields.

Reconstruction of pH-universal atomic FeNC catalysts towards oxygen reduction reaction

Constructing of single atom catalysts that can stably exist in various energy conversion and storage devices is still in its infancy. Herein, a geometrically optimized three-dimensional hierarchically architectural single atomic FeNC catalyst with fast mass transport and electron transfer is rationally developed by post-molecule pyrolysis assisted with silicon template and reconstructs by ammonia treating. The ammonia-assisted secondary pyrolysis not only compensates for the volatilization of nitrogen species contained in organic precursors but also optimizes the surface structure of FeNC catalyst, thus increasing the content of pyridinic nitrogen and boosting the density of active sites (FeN_x) in FeNC samples. In addition, the pyridinic nitrogen adjusts the electronic distribution in Fe 3d active center and promotes the catalytic performances. Therefore, this hollow spherical atomically dispersed FeNC catalyst delivers outstanding oxygen reduction reaction (ORR) activity in pH-universal electrolyte and surpasses the most reported values.

Binary nonmetal S and P-co-doping into mesoporous PtPd nanocages boosts oxygen reduction electrocatalysis

The development of doped noble metal catalysts with nonmetal elements to improve the catalytic performance toward the oxygen reduction reaction (ORR) is significant for proton exchange membrane fuel cell technology. Here, we report a one-pot for dual-nonmetal-doping strategy for the synthesis of S and P-co-doped mesoporous PtPd nanocages (PtPdSP mNCs) by using pre-synthesized mesoporous PtPd nanocages (PtPd mNCs) as the precursor and triphenylphosphine sulphide as both S and P sources. Benefitting from the combined advantages of metal-nonmetal incorporation, hollow cavity and surface porosity, the resultant quaternary PtPdSP mNCs exhibit outstanding ORR activity and long-term stability. This research work provides a good strategy for the doping of two or more selected nonmetallic elements into metallic nanocrystals with a controllable structure and composition.

Highly active electrocatalysts of iron phthalocyanine by MOFs for oxygen reduction reaction under alkaline solution

Metal-nitrogen-carbon materials (Fe-N/C) have been extensively studied as one of the most excellent electrocatalysts with good catalytic activities and cheap price towards the oxygen reduction reaction (ORR). The rational design of metal-organic framework (MOF) derived carbon materials with rapid mass transport ability and good stability is a great challenge to achieve. Herein, intensive research of Fe-N/C catalysts prepared from assembling MOFs with cheap iron phthalocyanine (FePc) for the ORR is innovatively carried out. A series of Fe-N/C nano-architectures are simply synthesized by a convenient assembling method under different temperatures (800 to 1000 °C). The assembly method at high temperatures tunes the number of FeN x active sites and intensifies the exposure of interior active sites. The highly dispersing Fe20-N/C electrocatalyst treated at 900 °C exhibits remarkable stability and excellent ORR activities with a half-wave potential of 0.866 V (vs. RHE) in alkaline solution, which is higher than that of commercial Pt/C (0.838 V vs. RHE) under the same test conditions. X-ray photoelectron spectroscopy results illustrate that incorporated MOFs interact with the active centre of FePc, tend to enhance the electron transition and to promote the kinetics of the ORR. Overall, highly dispersed Fe-N/C MOF-based materials are excellent non-precious metal electrocatalysts for energy and environmental applications.

Three-dimensional Pd-Ag-S porous nanosponges for electrocatalytic nitrogen reduction to ammonia

Electrochemical nitrogen reduction reaction (NRR) provides a facile and sustainable route to synthesize ammonia. The preparation of efficient and high-performance catalysts is one of the most important issues in large-scale applications of the electrochemical synthesis of ammonia. Herein, we have devised a simple method to fabricate three-dimensional palladium-silver-sulphur porous nanosponges (Pd-Ag-S PNSs) under room temperature. The porous network can provide more active sites and accessible channels for the reaction species. The incorporation of sulfur reduces the energy barrier of NRR and promotes the nitrogen hydrogenation to ammonia. Intrinsically, the Pd-Ag-S PNSs demonstrates a superior NRR performance with an NH3 yield of 9.73 μg h-1 mg-1cat. and a faradaic efficiency of 18.41% at -0.2 V, superior to those of the undoped Pd-Ag PNSs. The design of the three-dimensional metallic nanosponges with the doping of nonmetallic elements is a highly valuable strategy for NRR and other electrocatalytic reactions.

Co9 S8 -Catalyzed Growth of Thin-Walled Graphite Microtubes for Robust, Efficient Overall Water Splitting

Co₉ S₈ crystals can catalyze the growth of thin-walled graphite microtubes (GMTs) through a catalytic chemical vapor deposition (CCVD) process using thiourea as the precursor. The growth of GMTs follows a tip-growth mechanism with tube diameters up to a few micrometer. The hollow interiors of the GMTs are filled with carbon nanotubes and wrinkled graphene layers, which form a unique nanotube/graphene-in-microtube structure. As-formed GMTs are N,S-codoped with lots of Co₉ S₈ nanoparticles encapsulated in their inner walls. These GMTs are room-temperature ferromagnets and can be loaded on Ni foams to work as binder-free electrocatalysts with low overpotential (310 mV at 50 mA cm^-2 for the oxygen evolution reaction (OER) and 284 mV at 50 mA cm^-2 for the hydrogen evolution reaction (HER)) and long-term durability (continuous work for 120 h without loss in performance). Our research proves that metal sulfides can catalyze the growth of graphite microtubes and as-formed GMTs may potentially be used as functional building blocks to construct new kinds of electrochemical devices for various energy-related applications.