Non-precious Metal Catalysts Research Articles

Polymerizable Ionic Liquid-Derived N, S co-Doped sp3/sp2 Carbon as Electrocatalyst for H2O2 Generation.

The H2O2 generation via the green electrochemical process is of high interest. For the H2O2 electrochemical generation, the oxygen reduction reaction (ORR) is important. Unfortunately, the ORR is kinetically sluggish and catalysts are needed. However, noble metal ORR catalysts are pricy and scarcely applicable in applications. Therefore, non-precious metal catalysts are desired. Heteroatom-doped carbons show promise as metal-free ORR catalysts. The ORR catalytic activity will be enhanced by the carbon's sp2 and/or sp3 engineering. For N, S co-Cdoped and sp2/sp3 modulated carbon, a polymerizable ionic liquid of hydrolyzed vinyl imidazolium was studied. The carbon is studied as a metal-free catalyst for the ORR via the 2e- process. It is possible to get an onset potential of 0.88 V vs. RHE with approximately 50 % selectivity for the H2O2. The current study offers a simple technique for synthesizing heteroatom-doped sp2/sp3 designed carbon as catalysts for the electroreduction of O2 to produce H2O2, and a new way of tunning the sp3/sp2 carbon catalytic activity by modulating the ionic liquid.

Ultralow Ru-doped NiFe catalyst on stainless-steel fibers for enhanced oxygen evolution reaction in anion-exchange membrane water electrolysis

Designing high-performance, stable electrodes for the oxygen evolution reaction (OER) is essential for anion-exchange membrane water electrolysis (AEMWE) in industrial-scale hydrogen production. AEMWE has not yet been commercialized due to the high cost of precious metal catalysts and unsatisfactory performance of non-precious metal catalysts. Although various anodes are being developed to replace expensive Ir-based catalysts, low-cost catalysts that demonstrate a balance of performance and stability remain limited. In the present study, we fabricated a NiFe catalyst on a corrosion-resistant stainless-steel fiber paper substrate using a simple electrodeposition method and introduced small amounts of Ru via galvanic displacement. In half-cell tests, an enhanced overpotential of 229 mV was observed for the Ru-NiFe/SS anode at 10 mA/cm2. Using Ru-NiFe/SS as an anode for OER in AEMWE assembled with a commercial Pt/C cathode exhibited high performance with a current density of 8.73 A cm−2 (at 2.05 Vcell and 80℃). Long-term stability tests also showed that the Ru-NiFe/SS anode had higher stability than commercial IrO2 electrodes at 1 A cm−2 and 80℃ for 50 h. Therefore, Ru-NiFe/SS can be considered an alternative to conventional Ir-based electrodes to reduce hydrogen production costs.

Revealing OH species in situ generated on low-valence Cu sites for selective carbonyl oxidation

Catalytic oxidation through the transfer of lattice oxygen from metal oxides to reactants, namely the Mars-van Krevelen mechanism, has been widely reported. In this study, we evidence the overlooked oxidation route that features the in situ formation of surface OH species on Cu catalysts and its selective addition to the reactant carbonyl group. We observed that glucose oxidation to gluconic acid in air (21% O2) was favored on low-valence Cu sites according to X-ray spectroscopic analyses. Molecular O2 was activated in situ on Cu0/Cu+ forming localized, adsorbed hydroxyl radicals (*OH) which played the primary reactive oxygen species as confirmed by the kinetic isotope effect (KIE) study in D2O and in situ Raman experiments. Combined with DFT calculations, we proposed a mechanism of O2-to-*OH activation through the *OOH intermediate. The localized *OH exhibited higher selectivity toward glucose oxidation at C1HO to form gluconic acid (up to 91% selectivity), in comparison with free radicals in bulk environment that emerged from thermal, noncatalytic hydrogen peroxide decomposition (40% selectivity). The KIE measurements revealed a lower glucose oxidation rate in D2O than in H2O, highlighting the role of water (H2O/D2O) or its derivatives (e.g., *OH/*OD) in the rate-determining step. After proving the C1-H activation step kinetically irrelevant, we proposed the oxidation mechanism that was characterized by the rate-limiting addition of *OH to C1=O in glucose. Our findings advocate that by maneuvering the coverage and activity of surface *OH, high-performance oxidation of carbonyl compounds beyond biomass molecules can be achieved in water and air using nonprecious metal catalysts.

Review of AEM Electrolysis Research from the Perspective of Developing a Reliable Model

This review thoroughly examines recent progress, challenges, and future prospects in the field of alkaline exchange membrane (AEM) electrolysis. This emerging technology holds promise for eco-friendly hydrogen production. It blends the benefits of traditional alkaline and proton-exchange membrane technologies, enhancing affordability and operational efficiencies by utilizing non-precious metal catalysts and operating at reduced temperatures. This study discusses key developments in materials, electrode design, and performance enhancement techniques. It also highlights the strategic role of AEM electrolysis in meeting global energy transition targets, like achieving Net Zero Emissions by 2050. An in-depth exploration of the operational fundamentals of AEM water electrolysis is provided, noting the technology’s early stage development and the ongoing need for research in membrane-electrode assembly assessment, catalyst efficiency, and electrochemical ammonia production. Moreover, this review compiles results on different cell components, electrolyte types, and experimental approaches, providing insights into operational parameters critical to optimizing AEM performance. The conclusion emphasizes the necessity for continuous research and commercialization efforts to exploit AEM electrolysis’s full potential across diverse industries.

Encapsulating Transition Metal Nanoparticles inside Carbon (TM@C) Chainmail Catalysts for Hydrogen Evolution Reactions: A Review

Green hydrogen energy from electrocatalytic hydrogen evolution reactions (HERs) has gained much attention for its advantages of low carbon, high efficiency, interconnected energy medium, safety, and controllability. Non-precious metals have emerged as a research hotspot for replacing precious metal catalysts due to low cost and abundant reserves. However, maintaining the stability of non-precious metals under harsh conditions (e.g., strongly acidic, alkaline environments) remains a significant challenge. By leveraging the curling properties of two-dimensional materials, a new class of catalysts, encapsulating transition metal nanoparticles inside carbon (TM@C) chainmail, has been successfully developed. This catalyst can effectively isolate the active metal from direct contact with harsh reaction media, thereby delaying catalyst deactivation. Furthermore, the electronic structure of the carbon layer can be regulated through the transfer of electrons, which stimulates its catalytic activity. This addresses the issue of the insufficient stability of traditional non-precious metal catalysts. This review commences with a synopsis of the synthetic advancement of the engineering of TM@C chainmail catalysts. Thereafter, a critical discussion ensues regarding the electrocatalytic performance of TM@C chainmail catalysts during hydrogen production. Ultimately, a comprehensive review of the conformational relationship between the structure of TM@C chainmail catalysts and HER activity is provided, offering substantial support for the large-scale application of hydrogen energy.

Bimetallic MOF derived Cu3P/Co2P grown on coal-based carbon fibers as self-supporting electrocatalyst for enhanced hydrogen evolution

Transition metal phosphides (TMPs) are often considered as a cost-effective replacement for precious metal catalysts in hydrogen evolution reaction (HER). Herein, the fibers are produced by combining coal with electrospinning technology, and then undergoing a pre-oxidation process for transforming into pre-oxidized coal-based fibers. Subsequently, CuCo-metal organic framework (CuCo-MOF) is grown on the pre-oxidized coal-based fibers using solvothermal method, and the Cu3P/Co2P/coal-based carbon fibers (Cu3P/Co2P/C-CFs) composite catalyst is successfully fabricated by phosphating at low temperature and carbonizing at high temperature. The uniformly grown nanoparticles (NPs) on the surface of C-CFs enhance the electrochemically active area, while the electron transfer between Cu3P and Co2P effectively modulates the electronic structure, increasing the catalytic activity of the catalyst for HER. In addition, the flexible C-CFs not only serve as self-supporting electrode but also effectively inhibit the agglomeration of Cu3P/Co2P NPs. Remarkably, the overpotential of Cu3P/Co2P/C-CFs is 83 mV at 10 mA cm−2 current density for HER in 0.5 mol L−1 H2SO4 solution. This study presents promising strategies for the high value-added utilization of coal and the synthesis of highly effective non-precious metal catalysts.

Study on evaluating and optimizing surface property mechanisms of polyalloy for enhanced OER catalyses via electrodeposited technique coupled with molecular dynamics simulations

Polyalloy catalysts composed of non-precious metals exhibit considerable potentials for facilitating overall water splitting processes in alkaline environments. However, achieving evaluations and optimizations of surface property mechanisms of polyalloy for enhanced OER catalyses is the key scientific issue that urgently need to be solved. Electrodeposited technique coupled with molecular dynamics simulations (MDS) are the key to breaking through aforementioned bottlenecks. Moreover, accurately predicting selections of non-precious metal elements in these catalysts through molecular dynamics simulations poses a challenging task. Here, three distinct non-precious metal catalysts (i.e. Ni, NiCo, and NiCoFe) were successfully synthesized through a facile one-step electrodeposition approach under a three-electrode system, which were deposited onto carbon sheets. For the sake of evaluating catalytic properties, MDS were utilized to calculate contact angles on ideal surfaces, which were verified by experimental measurements. Furthermore, ternary alloy catalysts (i.e. NiCoFe) exhibited an overpotential of 254 mV at a current density of 10 mA cm2 and exhibited remarkable stability over a prolonged 150-hour testing period. Finally, main findings can further underscore potentials of utilizing electrodeposition to fabricate efficient non-precious metal catalytic electrodes for overall water splitting, as well as the feasibility of indirectly predicting electrocatalytic performances of such cost-effective catalysts via MDS.

Enhanced ammonia yield rate from nitrogen on collapsed dodecahedral-shaped Co/NC electrocatalyst

Nowadays, multi-component non-precious metal catalysts have been considered as a significant strategy for enhancing the yield of synthesizing NH3 by electrocatalytic nitrogen reduction reaction (E-NRR). In the present work, carbon composites doped with well-dispersed Co and N (Co/NC) were prepared by pyrolyzing zeolitic imidazolate framework-67 (ZIF-67) at various temperatures protected under a N2 flow. Co/NC exhibits a collapsed dodecahedral morphology with a mesoporous structure (3.5-4 nm). The chemical states of Co/N and the structural defects of C are closely related to the carbonization temperature. In a N2-saturated 0.1 M KOH electrolyte, the as-prepared catalysts exhibit an NH3 yield rate (Y(NH3)) of 60.57 μg h-1 mgcat.-1 and a Faradaic efficiency (FE) of 23.3% at -0.1 V (vs the reversible hydrogen electrode, RHE) at ambient conditions. The enhanced E-NRR activity of Co/NC may primarily originate from an associative distal pathway on the Co-N3-C sites and the carbon defects in an alkaline electrolyte. Specifically, this work presents a three-component E-NRR catalyst with excellent stability and great activity based on Co/NC.

Electrocatalysis of Co/CoxOy nanofilms supported by synchronously nitrogen-doped Ketjenblack carbon towards oxygen reduction reaction

Developing a highly active and stable non-precious metal catalyst for oxygen reduction reaction (ORR) is of great practical significance for advancing fuel cell technology. In this work, a continuous two-step hydrothermal reaction followed by high temperature pyrolysis were employed to achieve in situ N-doping preferentially into Ketjenblack carbon (KB-N) and composite of KB-N and Co/CoxOy nanofilms (Co/CoxOy-NFs) as Co/CoxOy-NFs@KB-N. The N-doped state strongly affects the ORR activity of catalyst. All prepared Co/CoxOy-NFs@KB-N catalysts exhibit observably improved ORR activity compared with the basal KB-N and N-doped Co/CoxOy-NFs, in which the optimal Co/CoxOy-NFs@KB-N catalyst demonstrate the positive Eonset (0.864 V) and E1/2 (0.788 V) vs. RHE, the low Tafel slope (69.27 mV dec−1), implying quick ORR kinetics. And, the Co/CoxOy-NFs@KB-N catalyst exhibits highly electrochemical durability. The KB-N substrate can purify Co valence in CoO component, promote amorphization of CoO crystalline structure and enhance the interaction between Co/CoxOy-NFs and KB-N in Co/CoxOy-NFs@KB-N catalyst. Thus electronic effect, structural effect and synergistic effect can strengthen O2 adsorption, provide enough adsorbed sites and accelerate electron transfer, resulting in prominent ORR performance of Co/CoxOy-NFs@KB-N catalyst.

Metal–Organic Skeleton-Derived W-Doped Ga2O3-NC Catalysts for Aerobic Oxidative Dehydrogenation of N-Heterocycles

N-heterocycles with quinoline structures hold significant importance within the chemical and pharmaceutical industries. However, achieving their efficient transformations remains a vital yet challenging endeavor. Herein, a series of W-doped Ga2O3-NC catalysts were synthesized using a Ga-MOF-derived strategy through a simple solvothermal method, with a remarkably high activity and selectivity towards the oxidative dehydrogenation of N-heterocycles. Furthermore, the MOF-derived W-doped Ga2O3-NC catalysts exhibit remarkable substrate tolerance and recyclability. The outstanding catalytic activity was attributed to the robust synergistic interaction between the W species and the Ga2O3-NC carrier, which facilitates the activation of hydrogen atoms in the C-H and C=N bonds on both the oxygen molecule and the substrate to produce H2O2. Additionally, the solvent effect of methanol can significantly enhance dehydrogenation due to its strong ability to donate and accept protons of hydrogen bonding. The present work provides a new approach to MOF-derived non-precious metal catalysts for achieving the efficient oxidation dehydrogenation of N-heterocycles.

Deciphering Anion Exchange Membrane Water Electrolysis: A Distribution of Relaxation Times Approach

Anion exchange membrane water electrolysis (AEM-WE) is a promising method for hydrogen production, offering advantages over proton exchange membrane water electrolysis (PEM-WE), such as the use of nonprecious metal catalysts and perfluorosulfonic acid free membranes. Despite achieving impressive current densities, challenges in efficiency and stability remain. This study employs electrochemical impedance spectroscopy (EIS), the equivalent circuit model (ECM) and distribution of relaxation times (DRT) analysis to investigate AEM-WE cells. DRT analysis identifies and quantifies five loss mechanisms within the AEM-WE system, including hydrogen and oxygen evolution reactions and ionic transport losses. Long-term experiments reveal catalyst degradation and its impact on performance, providing insights for targeted optimisation. The findings enhance understanding of the electrochemical processes in AEM-WE, offering pathways to improve stability and efficiency.

Deciphering Anion Exchange Membrane Water Electrolysis: A Distribution of Relaxation Times Approach

Anion exchange membrane water electrolysis (AEM-WE) is a promising method for hydrogen production, offering advantages over proton exchange membrane water electrolysis (PEM-WE), such as the use of nonprecious metal catalysts and perfluorosulfonic acid free membranes. Despite achieving impressive current densities, challenges in efficiency and stability remain. This study employs electrochemical impedance spectroscopy (EIS), the equivalent circuit model (ECM) and distribution of relaxation times (DRT) analysis to investigate AEM-WE cells. DRT analysis identifies and quantifies five loss mechanisms within the AEM-WE system, including hydrogen and oxygen evolution reactions and ionic transport losses. Long-term experiments reveal catalyst degradation and its impact on performance, providing insights for targeted optimisation. The findings enhance understanding of the electrochemical processes in AEM-WE, offering pathways to improve stability and efficiency.

Insights on the hydrogenation of furfural and its derivatives to 1,5-Pentanediol over Ni/La-substituted CeO2 catalysts

The discerning activation of specific bonds in furfural and its derivatives presents a formidable task in the realm of biomass refinement, necessitating the provision of a precisely tailored catalyst. In this work, 1,5-pentanediol was realized by direct hydrogenation of furfural over Ni/La-substituted CeO2 catalysts. The doping of La species significantly increased the oxygen vacancies, as well as leaded to expose more interfacial Niδ+-OV-LaxCe sites and optimize the metallic Ni electronic configuration. The Ni/3.0La2O3-CeO2 catalyst showcased a remarkable catalytic activity and high yield of 1,5-pentanediol (70 %), effectively reducing the activation energy required for the hydrogenation of furfural to 1,5-pentanediol (57.5 kJ mol−1). These findings surpassed the performances of Ni/La2O3, Ni/CeO2, and non-precious metal catalysts documented in existing literature. This outcome serves as a valuable reference for the controllable optimization of furfural directed hydrogenation catalysts, as well as provides theoretical support for the efficient and environmentally-friendly synthesis of 1,5-pentanediol.

Construction of high-efficiency Fe-MnO@Fe electrocatalyst for methanol and ethanol oxidation in alkaline medium

Abstract Acquiring effective, durable and economical non-precious metal electrocatalysts is crucial for the widespread utilization of fuel cells. In this work, an iron/manganese oxide nanocomposite (Fe-MnO@Fe) is synthesized as a novel electrocatalyst by direct-current (DC) arc plasma technology integrating transition metal and transition metal oxide. The Fe-MnO@Fe catalyst demonstrates excellent catalytic performance. By modulating the percentage of transition metal and transition metal oxide in the composite, the largest current density values of methanol and ethanol oxidation of the composite reach 20.18 and 7.83 mA/cm2, respectively. In addition, the composite catalyst exhibits excellent stability and conductivity, and the catalyst greatly reduces the experimental cost relative to the noble metal catalysts, indicating that the composite is a potential fuel cell catalyst candidate and provides an innovative concept for creation non-precious metal catalysts.

Nanowire arrays with abundant Cu–Ni interfaces for electroreduction of CO2 to ethylene

Electrochemical reduction of CO2 to ethylene (C2H4), driven by renewable electricity, represents a strategy for sustainable development and carbon neutrality. However, continuous production of C2H4 at high efficiency and low cost remains a significant challenge. Herein, a synergistic approach using non-precious metals was employed, and in situ construction of a nanoarray structure with abundant Cu–Ni interfaces (Ni/Cu NWs) on a gas diffusion layer (GDL) was performed. The atomic interactions at the interface significantly enhanced the efficiency of C–C coupling. The Faraday efficiency (FE) for C2H4 production reached 58.65 %, and the current density of 253.42 mA cm−2 at −1.1 V, markedly surpassing that of bare Cu nanowire (Cu NWs, 25.33 %). By virtue of the in-situ construction on the GDL, the Cu–Ni interface catalyst demonstrated excellent stability, operating under high current for more than 72 h. In situ infrared characterization and theoretical calculations demonstrate that the incorporation of Ni effectively enhanced the CO2 activation process, which is beneficial for the accumulation of key intermediate of C–C coupling. At the Cu–Ni interface, the energy barrier for C–C coupling was reduced, thereby effectively promoting the conversion of C2H4. This work presents a solution strategy for the interfacial engineering of non-precious metal catalysts.

Strong Electronic Metal-Support Interactions Enable the Increased Spin State of Co-N4 Active Sites and Performance for Acidic Oxygen Reduction Reaction.

Nonprecious metal catalysts, particularly M-N-C catalysts, are widely recognized as promising contenders for the oxygen reduction reaction (ORR). However, a notable performance gap persists between M-N-C catalysts and Pt-based catalysts under acidic conditions. In this study, hybrid catalysts comprising single Co atoms and ultralow concentrations of Pt3Co intermetallic nanoparticles (NPs) are introduced to enhance ORR performance. Under acidic conditions, these hybrid catalysts demonstrate ORR efficiency with a half-wave potential of 0.895 V, negligible decay even after 80 000 cycles, and a high maximum power density of 1.34 W cm-2 in fuel cells. This performance surpasses those of Co-N-C and Pt/Co-N-C catalysts. Both experimental findings and theoretical computations suggest that the heightened ORR activity stems from an increase in the spin density of Co sites induced by noble metal NPs, facilitating the activation of O-O bonds via side-on overlapping and enabling a transition in the reaction pathway from associative to dissociative processes. This research offers a promising avenue for the systematic design of M-N-C cathodes with an enhanced performance for acidic fuel cells.

Hydrogen production mechanism and catalytic productivity of Ni-X@g-C3N4 (X = precious and non-precious promoter metals) catalysts from KBH4 hydrolysis under stress loading and atmospheric pressure: Experimental analysis and molecular dynamics approach

In this study, the pressure effect of Ni-based catalysts added a second promoter metal to increase of catalyst performance supported a graphite carbon nitride (g-C3N4) monolayer on hydrogen release mechanisms from potassium boron hydride (KBH4) hydrolysis was investigated using molecular dynamics (MD) method based on tight-binding density functional theory (DFT). The use of the various promoters, such as transition metals (X = Cu, Ta and W) and noble metals (X = Pd, Pt and Rh) with applying a high external pressure was investigated to understand the role on catalytic performance of the Ni-based catalysts under stress loading. The g-C3N4 monolayer doped with Ni-X nano-catalysts was used for efficient H2 release from KBH4 hydrolysis. The computational results show that the number of H2 shows more increment with MD time for NiW and NiRh catalysts than other NiTa and NiCu (transition metals) and NiPd and NiPt (noble metals) under 0 GPa pressure. On the other hand, a notable increase in H2 amount is seen only NiCu and NiRh catalysts under 50 GPa. Also, the mechanism of the H2 production reaction from KBH4 hydrolysis of g-C3N4 doped NiCo catalysts was clarified. High-performance cost metal catalysts such as NiCo was investigated as both experimentally and modeling under atmospheric pressure to enhance its commercial application value. Some experimental applications and analyzes were also performed to measure the accuracy of the modeling for the relevant molecular groups in the system.

Enhancing hydrogen evolution reaction performance through defect engineering in WTeX (X= S, Se) monolayers: A first-principles study

Finding a novel material to substitute the existing noble metal catalysts for the hydrogen evolution reaction (HER) is essential for the further advancement of water electrolysis technology. Herein, we investigated the feasibility of using defect engineering to improve the hydrogen evolution reaction (HER) catalytic performance of WTeX (X = Se, S) materials in the 2H, 1 T, and 1 T′ phases. The results demonstrate that the introduction of defects significantly enhances WTeX monolayers’ HER performance. As exemplary cases, the Gibbs free energy changes for 2H WTeSe with a Te vacancy (2H WTeSe–VTe) and 2H WTeS with a Te vacancy (2H WTeS–VTe) are 0.029 eV and −0.002 eV, respectively. It was found that the active sites in 2H WTeSe–VTe and 2H WTeS–VTe have a substantial number of empty anti-bonding states, which increases the bond strength between H and the catalyst, leading to exceptional catalytic performance. This work demonstrates the feasibility of defect-engineered WTeX structures as electrocatalysts and provides a reliable reference for the study of non-precious metal catalysts.

Enhancement of electrocatalytic oxygen evolution performance for FeCrNiCoTi alloys via powder modification

The development of non-precious metal catalysts with excellent performance in the oxygen evolution reaction (OER) is crucial for large-scale and low-cost hydrogen production from water. FeCrNiCoTi multi-principal element alloy (MPEA), which is free of precious metals and possesses four specific effects, holds promise as a low-cost and efficient electrocatalyst for water electrolysis. However, further enhancing the exposure of its active sites remains a challenge. To address this issue, the FeCrNiCoTi MPEA powder was long-term mechanically milled to refine the grain size, introduce defects, and (oxygen) hydroxide species with the aim of improving OER catalytic performance. Such powder milled after 80 h exhibits an overpotential of 296 mV at 10 mA/cm2 and the Tafel slope of 41.3 mV/dec, with continuous stability for 40 h in 1.0 M KOH electrolyte, comparable to the commercial RuO2 catalyst. This work provides a simple, practical and effective approach for the preparation of high-performance, low-cost OER electrocatalysts.

Alkene Isomerization Catalyzed by a Mn(I) Bisphosphine Borohydride Complex.

An additive-free manganese-catalyzed isomerization of terminal alkenes to internal alkenes is described. This reaction is implementing an inexpensive nonprecious metal catalyst. The most efficient catalyst is the borohydride complex cis-[Mn(dippe)(CO)2(κ2-BH4)]. This catalyst operates at room temperature, with a catalyst loading of 2.5 mol %. A variety of terminal alkenes is effectively and selectively transformed into the respective internal E-alkenes. Preliminary results show chain-walking isomerization at an elevated temperature. Mechanistic studies were carried out, including stoichiometric reactions and in situ NMR analysis. These experiments are flanked by computational studies. Based on these, the catalytic process is initiated by the liberation of "BH3" as a THF adduct. The catalytic process is initiated by double bond insertion into an M-H species, leading to an alkyl metal intermediate, followed by β-hydride elimination at the opposite position to afford the isomerization product.