High-performance Electrocatalysts Research Articles

Molten-Salt Electrochemical-Assisted Synthesis of the CeO2-OV@GC Composite-Supported Pt Clusters with a Pt-O-Ce Structure for the Oxygen Reduction Reaction.

Highly active and robust Pt-based electrocatalysts for an oxygen reduction reaction (ORR) are of crucial significance for the development of proton exchange membrane fuel cells (PEMFCs). Herein, the high-loading and well-dispersive Pt clusters on graphitic carbon-supported CeO2 with abundant oxygen vacancies (PtAC/CeO2-OV@GC) were successfully fabricated by a molten-salt electrochemical-assisted method. The bonding of Pt with the highly electronegative O induces charge redistribution through the Pt-O-Ce structure, thus reducing the adsorption energies of oxygen-containing species. Such a PtAC/CeO2-OV@GC electrocatalyst exhibits a greatly enhanced ORR performance with a mass activity of 0.41 ± 0.02 A·mg-1Pt at 0.9 V versus a reversible hydrogen electrode, which is 2.7 times the value of a commercial Pt/C catalyst and shows negligible activity decay after 20000 cycles of accelerated degradation tests. It is anticipated that this work will provide enlightening guidance on the controllable synthesis and rational design of high-performance Pt-based electrocatalysts for PEMFCs.

Salt-Assisted, In Situ Current Nanowelding of an Interfacial Au Nanoparticle Film for a High-Performance Electrocatalyst.

Interfacial self-assembly is a well-established method for the preparation of a two-dimensional (2D) metal nanofilm from nanoscale building blocks. However, the as-prepared nanofilm exhibits limited conductivity because of the large contact resistance at the junctions among its building blocks. Here, we report a salt-assisted, in situ current nanowelding strategy to weld an interfacial Au nanoparticle (NP) film for downstream applications, such as high-performance electrocatalysts. Particularly, we found that salt-assisted interfacial assembly can reduce the size of the nanogaps among neighboring Au NPs and, in turn, greatly improve the conductivity of the resultant Au NP film. Consequently, the Au NP film can be readily welded using current, and the welding extent can be monitored in real-time by looking at the passing current. The welding finally produces a nanoporous Au film (NPGF) with a network nanostructure, high conductivity, and abundant active sites so that it delivers a large current density of 86.96 μA·cm-2 (1.81 times higher than that from the pristine Au NP film) and shows improved cycling stability for methanol electrooxidation. Thus, these results offer a low-cost, solution-processable approach for the fabrication of a large-area, interconnected nanofilm from nanoscale building blocks beyond Au NPs, which may find diverse downstream applications.

Rational Construction of Pt Incorporated Co3O4 as High-Performance Electrocatalyst for Hydrogen Evolution Reaction

Electrocatalysts in alkaline electrocatalytic water splitting are required to efficiently produce hydrogen while posing a challenge to show excellent performances. Herein, we have successfully synthesized platinum nanoparticles incorporated in a Co3O4 nanostructure (denoted as Pt-Co3O4) that show superior HER activity and stability in alkaline solutions (the overpotentials of 37 mV to reach 10 mA cm−2). The outstanding electrocatalytic activity originates from synergistic effects between Pt and Co3O4 and increased electron conduction. Theoretical calculations show a significant decrease in the ΔGH* of Co active sites and a remarkable increase in electron transport. Our work puts forward a special and simple synthesized way of adjusting the H* adsorption energy of an inert site for application in HER.

Heterojunction engineering via in-situ electrochemical reconstruction for boosting electrocatalytic biomass upgrading-coupled hydrogen production

Rationally designing and constructing high-performance electrocatalysts is critical for environmental and sustainable electrocatalytic biomass upgrading coupled with hydrogen evolution. Herein, we developed a novel in-situ electrochemical reconstruction strategy to fabricate heterostructured electrocatalysts for efficient biomass upgrading-coupled hydrogen production. Through in-situ anodic and cathodic electrochemical reconstructions, Ni(OH)2-CuO nanorods assembled by nanosheets with abundant low-crystalline Ni(OH)2/crystalline CuO heterojunctions on Cu foam (Ni(OH)2-CuO/CF) and S-doped Ni(OH)2-Cu2O nanofoam formed by cross-linked nanoparticles on CF (Ni(OH)2-Cu2O(S)/CF) were respectively constructed for electrocatalytic 5-hydroxymethylfurfural oxidation reaction (HMFOR) and hydrogen evolution reaction (HER). For the Ni(OH)2-CuO/CF, the overall configuration of nanorods assembled by self-standing nanosheets ensures good conductivity, full exposure of active sites, and fast mass/electron transfer. The abundant Ni(OH)2/CuO heterojunctions provide dual active sites of Ni and Cu to simultaneously adsorb and activate hydroxyl and aldehyde groups in HMF. The electronic interaction between Ni(OH)2 and CuO accelerates the reversible conversion of Ni2+↔Ni3+ to generate more Ni3+ active species and enhances the intrinsic activity of dual active sites to reduce the reaction energy barrier of the rate-determining step. As a result, the Ni(OH)2-CuO/CF shows superior HMFOR performance, with a HMF conversion of 99.3%, a FDCA yield of 98.1%, and stability for 50 cycles in 10 mM HMF+1.0 M KOH medium. Meanwhile, the Ni(OH)2-Cu2O(S)/CF also exhibits remarkable HER activity with an overpotential of only 64.7 mV at 10 mA cm−2 in 1.0 M KOH solution due to its unique structure and composition. When coupling a two-electrode system, the HMFOR-HER system achieves a current density of 10 mA cm−2 at 1.44 V, 221 mV lower than that of the OER-HER system. This work provides an in-situ electrochemical reconstruction strategy for designing advanced heterojunction-rich electrocatalysts for various electrocatalytic applications.

Efficient and durable seawater electrolysis with a V2O3-protected catalyst.

The ocean, a vast hydrogen reservoir, holds potential for sustainable energy and water development. Developing high-performance electrocatalysts for hydrogen production under harsh seawater conditions is challenging. Here, we propose incorporating a protective V2O3 layer to modulate the microcatalytic environment and create in situ dual-active sites consisting of low-loaded Pt and Ni3N. This catalyst demonstrates an ultralow overpotential of 80 mV at 500 mA cm-2, a mass activity 30.86 times higher than Pt-C and maintains at least 500 hours in seawater. Moreover, the assembled anion exchange membrane water electrolyzers (AEMWE) demonstrate superior activity and durability even under demanding industrial conditions. In situ localized pH analysis elucidates the microcatalytic environmental regulation mechanism of the V2O3 layer. Its role as a Lewis acid layer enables the sequestration of excess OH- ions, mitigate Cl- corrosion, and alkaline earth salt precipitation. Our catalyst protection strategy by using V2O3 presents a promising and cost-effective approach for large-scale sustainable green hydrogen production.

Atomic Molybdenum Nanomaterials for Electrocatalysis.

As a sustainable energy technology, electrocatalytic energy conversion requires electrocatalysts, which greatly motivates the exploitation of high-performance electrocatalysts based on nonprecious metals. Molybdenum-based nanomaterials have demonstrated promise as electrocatalysts because of their unique physiochemical and electronic properties. Among them, atomic Mo catalysts, also called Mo-based single-atom catalysts (Mo-SACs), have the most accessible active sites and tunable microenvironments and are thrivingly explored in various electrochemical conversion reactions. A timely review of such rapidly developing topics is necessary to provide guidance for further exploration of optimized Mo-SACs toward electrochemical energy technologies. In this review, recent advances in the synthetic strategies for Mo-SACs are highlighted, focusing on the microenvironment engineering of Mo atoms. Then, the representative achievements of their applications in various electrocatalytic reactions involving the N2, H2O, and CO2 cycles are summarized by combining experimental and computational results. Finally, prospects for the future development of Mo-SACs in electrocatalysis are provided and the key challenges that require further investigation and optimization are highlighted.

Construction of a p-p heterojunction Co3O4/MoS2 electrocatalyst for boosting hydrogen evolution reaction

Building p-p heterojunctions with Fermi level difference, due to the motion of energy levels, band bending, and internal electric field generation, can effectively improve the electronic structure of the interface, enrich the active sites of heterojunctions, and promote the adsorption of reaction intermediates, which is an effective approach to constructing high-performance electrocatalysts. In this study, a Co3O4/MoS2 p-p heterojunction catalyst with nano-particle/nano-flower structure was designed, inducing charge transfer from Co3O4 to MoS2, thereby increasing the negative charge of MoS2, improving *H adsorption through electrostatic interaction, enhancing electrocatalytic kinetics, and reducing reaction overpotential. The catalytic performance of MoS2 for hydrogen evolution reaction was effectively enhanced. In 1 M KOH solution, the current density was 10 mA cm−2, and the overpotential was 156 mV, with good stability after 40 hours of operation. This work provides a new direction for the design of p-p heterojunction electrocatalysts and offers more choices for promoting the development of high-performance non-noble metal catalysts.

Insights into the Origin of Activity Enhancement via Tuning Electronic Structure of Cu2O towards Electrocatalytic Ammonia Synthesis.

The insight of the activity phase and reaction mechanism is vital for developing high-performance ammonia synthesis electrocatalysts. In this study, the origin of the electronic-dependent activity for the model Cu2O catalyst toward ammonia electrosynthesis with nitrate was probed. The modulation of the electronic state and oxygen vacancy content of Cu2O was realized by doping with halogen elements (Cl, Br, I). The electrocatalytic experiments showed that the activity of the ammonia production depends strongly on the electronic states in Cu2O. With increased electronic state defects in Cu2O, the ammonia synthesis performance increased first and then decreased. The Cu2O/Br with electronic defects in the middle showed the highest ammonia yield of 11.4 g h-1 g-1 at -1.0 V (vs. RHE), indicating that the pattern of change in optimal ammonia activity is consistent with the phenomenon of volcano curves in reaction chemistry. This work highlights a promising route for designing NO3-RR to NH3 catalysts.

Synthesis of Stable and Efficient Electrocatalysts for Hydrogen Evolution: Hierarchical NiMo-Based Hollow Nanotubes

Large-scale development of low-cost, efficient, and stable powder electrocatalysts for the hydrogen evolution reaction (HER) in alkaline solutions is a key step toward commercial hydrogen production. Herein, a hierarchical NiMo-MoO3-x hollow nanotube (NiMo-MoO3-x-HNT) with bifunctional groups as an efficient HER electrocatalyst was strategically invented using an MoO3 nanorod (MoO3−NR) as the precursor. The synthesis mechanism of the NiMo-MoO3-x-HNT is established based on in-depth investigations using diffraction, spectral, and microscopy results. Experimental results suggest that the NiMo-MoO3-x-HNT exhibits excellent electrocatalytic HER performance in 1 M KOH, with a low overpotential of 26.5 mV@10.0 mA cm-2 and a small Tafel slope of 32.6 mV dec–1. These values are comparable to those of cutting-edge electrocatalysts based on platinum-group metals. Moreover, it exhibits an almost unaffected cyclic stability over 50,000 cycles and robust durability over 98 h. This remarkable performance is attributed to its bifunctional groups and the porous hierarchical hollow nanotubular morphology. In summary, this study proposes a novel, efficient, and cost-effective strategy for the development of noble metal-free, high-performance HER electrocatalysts.

Lattice-dislocated bismuth nanowires formed by in-situ chemical etching on copper foam for enhanced electrocatalytic CO2 reduction

Electrochemical CO2 reduction reaction (CO2RR) to HCOOH is one of the most feasible and economical methods to achieve carbon neutrality. Bismuth (Bi), as a metal catalyst for CO2RR, is considered to have great potential for application and has been widely studied due to its high formate selectivity, low toxicity, cheapness, and abundance. Unfortunately, low current density and short electrode lifetime have hindered its progress towards practical applications. In this work, we present a method that enables the chemical etching of Bi on Cu, which is capable of spontaneously accomplishing the loading of Bi on Cu foam in the liquid phase at room temperature. Additionally, to provide more abundant catalytically active sites, twisted Bi nanowires (BiNWs) with lattice dislocations were successfully prepared on the surface of Cu foam using a three-step chemical method involving oxidation, reduction, and in-situ etching. The Cu Foam@BiNWs was found to be a highly active electrocatalyst for CO2 reduction to formate at a low applied potential, achieving a faradaic efficiency for formate (FEFormate) of 95 % and a formate partial current density of ∼ 12 mA cm−2 at −0.78 V vs. RHE (reversible hydrogen electrode). Even within such a wide potential window of −0.68 ∼ -1.08 V vs. RHE, the FEFormate is consistently above 90 %. Such exceptional CO2 reduction activity can be attributed to the distortions and lattice dislocations present in the surface BiNWs. Furthermore, the Cu Foam@BiNWs electrode demonstrated a total current density close to 100 mA cm−2 at −0.98 V in an alkaline flow cell, while maintaining excellent catalytic stability over a prolonged 30-hour period of high current density electrochemical activity, thus showing potential for advancing the industrialisation of formate production. This work emphasizes the crucial role of size-dependent catalysis and crystal defect engineering strategies in the field of electrocatalysis, elucidates the mechanism of the rate-determining step (RDS) in the electrocatalytic CO2 reduction process on the developed catalysts, which can provide valuable insights into the design and development of high performance electrocatalysts not only in CO2RR but also in other fields.

Electrocatalytic Oxygen Reduction Using Metastable Zirconium Suboxide.

Strategies for discovery of high-performance electrocatalysts are important to advance clean energy technologies. Metastable phases such as low temperature or interfacial structures that are difficult to access in bulk may offer such catalytically active surfaces. We report here that the suboxide Zr3O, which is formed at Zr-ZrO2 interfaces but does not appear in the experimental Zr-O phase diagram exhibits outstanding oxygen reduction reaction (ORR) performance surpassing that of benchmark Pt/C and most transition metal-based catalysts. Addition of Fe3C nanoparticles to give a Zr-Zr3O-Fe3C/NC catalyst (NC = nitrogen-doped carbon) gives a half-wave potential (E1/2) of 0.914 V, outperforming Pt/C and showing only a 3 mV decrease after 20,000 electrochemical cycles. A zinc-air battery (ZAB) using this cathode material has a high power density of 241.1 mW cm-2 and remains stable for over 50 days of continuous cycling, demonstrating potential for practical applications. Zr3O demonstrates that interfacial or other phases that are difficult to stabilize may offer new directions for the discovery of high-performance electrocatalysts.

Nickel-doped cobalt phosphide with phosphorus-vacancy-abundant as an efficient catalyst for non-aqueous and quasi-solid-state Li–O2 batteries

High-performance electrocatalysts are required to tackle the challenges for Li-O2 batteries. Elemental doping and vacancy engineering can modify the local electronic structure, and thus enhance the adsorption and catalytic activity. Nickel-doped cobalt phosphides, rich in phosphorus vacancies, are synthesized to boost the electrochemical efficiency in Li-O2 batteries. These nanocomposites exhibit high performance in non-aqueous Li-O2 batteries, with low overpotential and cycling stability up to 741 cycles at 500 mAh/g. Additionally, with quasi-solid-state electrolytes, the batteries can retain operation for 91 cycles. This study underscores the potential of elemental doping and vacancy engineering in transition-metal-phosphides for Li-O2 battery development.

Substantial Electrocatalytic Oxygen Evolution Performances of Activated Carbon-Decorated Vanadium Pentoxide Nanocomposites

Developing the ecofriendly and high-fidelity electrocatalysts for the oxygen evolution reaction (OER) is essential to foster effective production of environmentally friendly hydrogen. Herein, we fabricated the highly efficient OER electrocatalysts of the activated carbon-decorated vanadium pentoxide (AC-V2O5) nanocomposites using a facile hydrothermal technique. The AC-V2O5 nanocomposites displayed an aggregated structure of the AC nano-sheet-anchored orthorhombic V2O5 nanorods. When performing the OER process in an alkaline electrolyte at 10 mA/cm2, AC-V2O5 exhibited the low overpotential (~230 mV), small Tafel slope (~54 mV/dec), and excellent stability. These substantial OER performances of AC-V2O5 could be ascribed to the synergistic effects from both the electrochemically active V2O5 nanorods and the highly conductive AC nanosheets. The results infer that the AC-V2O5 nanocomposites possess a substantial aptitude as a high-performance OER electrocatalyst for production of the future green energy source—hydrogen.

Self-Ordered Anodic Porous Oxide Layers as a High Performance Electrocatalyst for Water Oxidation

Self-Ordered Anodic Porous Oxide Layers as a High Performance Electrocatalyst for Water Oxidation

Activating Inert Perovskite Oxides for CO2 Electroreduction via Slight Cu2+ Doping in B-Sites.

Perovskite oxides are proven as a striking platform for developing high-performance electrocatalysts. Nonetheless, a significant portion of them show CO2 electroreduction (CO2RR) inertness. Here a simple but effective strategy is reported to activate inert perovskite oxides (e.g., SrTiO3) for CO2RR through slight Cu2+ doping in B-sites. For the proof-of-concept catalysts of SrTi1-xCuxO3 (x=0.025, 0.05, and 0.1), Cu2+ doping (even in trace amount, e.g., x=0.025) can not only create active, stable CuO6 octahedra, increase electrochemical active surface area, and accelerate charge transfer, but also significantly regulate the electronic structure (e.g., up-shifted band center) to promote activation/adsorption of reaction intermediates. Benefiting from these merits, the stable SrTi1-xCuxO3 catalysts feature great improvements (at least an order of magnitude) in CO2RR activity and selectivity for high-order products (i.e., CH4 and C2+), compared to the SrTiO3 parent. This work provides a new avenue for the conversion of inert perovskite oxides into high-performance electrocatalysts toward CO2RR.

Metal-support interface engineering for stable and enhanced hydrogen evolution reaction

Hydrogen has emerged as a green and sustainable pathway towards achieving global decarbonization and net-zero emissions, intensely driving the need for efficient hydrogen production protocols. Electrocatalytic hydrogen evolution reaction (HER) holds great potential as a scalable, eco-friendly and safe avenue for efficient hydrogen production. However, the large-scale implementation of electrocatalytic HER is substantially challenged by the high-cost and unstable materials that are mainly fabricated from noble metals, e.g., Pt and Pd. Given this challenge, we adopted an interface engineering strategy to immobilize nanoscale Pt particles within the framework of nitrogen-doped CNTs, namely Pt@N-CNTs, where electronic metal-support interaction (EMSI) plays an important role in enabling orbital rehybridization and regulating the charge transfer through the metal-support interface, thereby considerably improving the electrocatalytic activity. With limited content of noble metals, our developed Pt@N-CNTs delivered superior HER performance with an ultralow overpotential of 5.8 mV at 10 mA cm−2 and demonstrated a high mass activity of 12.72 A mgPt−1 at an overpotential of 50 mV as well as excellent stability under harsh acidic conditions. At 500 mA cm−2, Pt@N-CNTs surprisingly exhibited an overpotential of 55.2 mV, outperforming that of commercial 20 wt% Pt/C catalysts (131.5 mV). Importantly, we established a straightforward, scalable, and time-saving microwave reduction strategy, alluding to its promising commercial viability. This work therefore sheds light on the development of high-performance electrocatalysts for hydrogen evolution and water electrolysis.

Work Function-Guided Electrocatalyst Design.

The development of high-performance electrocatalysts for energy conversion reactions is crucial for advancing global energy sustainability. The design of catalysts based on their electronic properties (e.g., work function) has gained significant attention recently. Although numerous reviews on electrocatalysis have been provided, no such reports on work function-guided electrocatalyst design are available. Herein, a comprehensive summary of the latest advancements in work function-guided electrocatalyst design for diverse electrochemical energy applications is provided. This includes the development of work function-based catalytic activity descriptors, and the design of both monolithic and heterostructural catalysts. The measurement of work function is first discussed and the applications of work function-based catalytic activity descriptors for various reactions are fully analyzed. Subsequently, the work function-regulated material-electrolyte interfacial electron transfer (IET) is employed for monolithic catalyst design, and methods for regulating the work function and optimizing the catalytic performance of catalysts are discussed. In addition, key strategies for tuning the work function-governed material-material IET in heterostructural catalyst design are examined. Finally, perspectives on work function determination, work function-based activity descriptors, and catalyst design are put forward to guide future research. This work paves the way to the work function-guided rational design of efficient electrocatalysts for sustainable energy applications.

Single-cluster anchored on PC6 monolayer as high-performance electrocatalyst for carbon dioxide reduction reaction: First principles study

Tremendous challenges remain to develop high-efficient catalysts for carbon dioxide reduction reaction (CO2RR) owing to the poor activity and low selectivity. However, the activity of catalyst with single active site is limited by the linear scaling relationship between the adsorption energy of intermediates. Motivated by the idea of multiple activity centers, triple metal clusters (M = Cr, Mn, Fe, Co, Ni, Cu, Pd, and Rh) doped PC6 monolayer (M3@PC6) were constructed in this study to investigate the CO2RR catalytic performance via density functional theory calculations. Results shows Mn3@PC6, Fe3@PC6, and Co3@PC6 exhibit high activity and selectivity for the reduction of CO2 to CH4 with limiting potentials of −0.32, −0.28, and −0.31 V, respectively. Analysis on the high-performance origin shows the more binding sites in M3@PC6 render the triple-atom anchored catalysts (TACs) high ability in regulating the binding strength with intermediates by self-adjusting the charges and conformation, leading to the improved performance of M3@PC6 than dual-atom doped PC6. This work manifests the huge application of PC6 based TACs in CO2RR, which hope to prove valuable guidance for the application of TACs in a broader range of electrochemical reactions.

Surface nitrided CuBi2O4 electrocatalysts with excellent selectivity for CO2 reduction to methanol

Developing a high-performance electrocatalyst for converting CO2 into methanol is of utmost importance. However, poor selectivity, and unavoidable competitive hydrogenolysis reaction (HER) are still challenges to be solved. In this study, a surface nitrided strategy was designed to synthesize a series N-copper-bismuth bimetallic oxide electrocatalysts (NCBO-t, t = 1, 2, 4 h) for CO2RR. The electrocatalyst NCBO-2 demonstrated a selectivity for methanol reaching 86.43 %, along with an impressive long-term stability lasting for 11 h, all achieved at a relatively low potential of −0.9 V. Experimental results and density functional theory (DFT) calculations indicated the introduction of nitrogen facilitates methanol production by optimizing binding of the reaction intermediate *OCH while promotes Faradaic efficiency of methanol products by suppressing the competitive HER, resulting in high Faradaic efficiency, current density, and stability of CO2RR at low overpotentials. This study offers a feasible idea for synthesis of high-performance CO2 methanol by electroreduction.

Facile synthesis of coral-like nitrogen and sulfur co-doped carbon-encapsulated FeS2 for efficient electroreduction of nitrate to ammonia

Electro-reduction of nitrate (NO3–) to ammonia is a promising method to transform the environmental contaminant NO3– to value-added ammonia. Since diverse end-products might be formed and a convenient material preparation process is preferable, it is of great importance to facilely synthesize a high-performance electro-catalyst towards ammonia generation with high selectivity. Herein, a coral-like nitrogen (N) and sulfur (S) co-doped carbon-encapsulated FeS2 composite material (FeS2@NSC) was successfully fabricated for effective electro-reduction of high-concentration of NO3– to ammonia through a simple one-step pyrolysis method. The FeS2@NSC-400 material exhibited remarkable electrocatalytic NH3 production performance with the NH3 yield of 4428.35 μg h−1 cm−2 and NH3 Faraday efficiency of 84.75 % at −1.4 V vs. Ag/AgCl, which outperforms many of the reported electrocatalysts. The unique small cluster coral-like core–shell structure, N, S co-doping and the interaction between inner FeS2 and the outer carbon layer greatly enhanced the electrical conductivity and stability of the material and the adsorption of NO3– and intermediate products, thereby facilitating the electrocatalytic performance of nitrate-to-ammonia. The FeS2@NSC material induced the electrocatalytic reduction of NO3– mainly through direct electron transfer instead of the indirect atomic H* mediation, and the main reduction product NH3 was speculated to derive from the pathway of NO3–* → NO2–* → NO* → HNO* → H2NO* → H2NOH* → NH3.