Non-precious Metal Research Articles

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.

Hierarchical Superhydrophilic/Superaerophobic Ni3S2/VS2 Nanorod-Based Bifunctional Electrocatalyst Supported on Nickel Foam for Overall Urea Electrolysis.

The design and preparation of effective nonprecious metal-based catalysts for the urea oxidation reaction (UOR) coupled with the hydrogen evolution reaction (HER) are of great significance to solve both energy shortage and environmental pollution problems. In this study, a novel hierarchical superhydrophilic and superaerophobicity three-dimensional nanorod-like bifunctional catalyst with a heterostructure (Ni3S2/VS2) was prepared on nickel foam via a simple one-step hydrothermal method, serving as an excellent electrocatalyst for both UOR and HER. The formed heterostructure significantly alters the electronic structure, optimizing charge transfer and increasing the number of active sites, which enhances the electrocatalytic performance of Ni3S2/VS2. As a result, this catalyst requires an extremely low potential of 1.396 V at the current density of 100 mA cm-2 for UOR and only 164 mV overpotential at -10 mA cm-2 for HER. Notably, a constructed two-electrode electrolyzer system (Ni3S2/VS2∥Ni3S2/VS2) demonstrates extraordinary activity and long-term stability, achieving a current density of 10 mA cm-2 at a low cell voltage of 1.48 V, which is superior to majority of the reported catalysts. This work demonstrates that the formation of heterostructures can effectively enhance the catalytic activity of nanomaterials toward UOR and HER and provides a feasible strategy for fabricating highly efficient nonprecious metal overall urea electrocatalysts.

NiCoMn phosphides-based 3D nanoflowers as universal electrocatalyst towards hydrogen evolution reaction at all pH values

In addressing the pH constraints encountered in real-world electrolyte environments, it is of great practical significance to establish a universal electrocatalyst capable of facilitating the hydrogen production reaction (HER) across all pH levels. Herein, non-precious metals NiCoMn were incorporated into a nickel foam skeleton and subjected to phosphorization treatment, yielding the NiCoMn-O-P@NF catalyst suitable for HER across the entire pH spectrum. Leveraging the synergistic effects of these three metals and phosphating regulation, the synthesized NiCoMn-O-P@NF demonstrates efficient HER catalytic performance in acidic (−0.05 VRHE at 10 mA cm−2), alkaline (−0.17 VRHE at 10 mA cm−2), and neutral (−0.25 VRHE at 10 mA cm−2) electrolytes, with exceptional stability. This study presents a cost-effective electrocatalyst with robust and enduring catalytic performance for HER over the full pH range, offering an environmentally friendly solution to the challenges of practical hydrogen generation.

The Role of Frustrated Lewis Pair in Catalytic Transfer Hydrogenation of Furfural using Nickel Single-Atom Catalysts: A Theoretical Study.

The burgeoning field of frustrated Lewis pair (FLP) heterogeneous catalysts has garnered significant interest in recent years, primarily due to their inherent ability to activate H-source molecules, such as H2, thereby facilitating hydrogenation reactions. However, the application of single metal atom catalysts incorporating FLP sites has been relatively under-explored. In this study, non-precious transition metal atoms were anchored onto a C2N framework with an intrinsic cavity and a defective N-C sheet. Theoretical calculations substantiated energy barriers as low as 0.10 eV for isopropanol activation, thereby positioning these catalysts as highly promising candidates for catalytic transfer hydrogenation of furfural. Electronic structure analyses revealed that the H-O bond breakage in isopropanol molecules was significantly facilitated by the presence of FLP sites within the catalysts. Notably, both Ni-C2N and Ni-N6-C demonstrated exceptional potential as selective catalysts for the hydrogenation of furfural into furfuryl alcohol, exhibiting remarkably low barriers of only 0.65-0.72 eV for the rate-determining steps, which are notably lower than those observed in many traditional catalysts. Theoretical investigations strongly imply that the construction of single atom catalysts with FLP sites could significantly enhance the activity and selectivity for hydrogenation reactions, thus stimulating the experimental synthesis of such catalysts.

A core-shell structured catalyst for enhanced oxygen evolution: NiFe double hydroxide coating over phosphorus -modified NiMoO4 nanorod cores

In this paper, we innovatively employed low-temperature phosphorization technology to successfully incorporate P doping into NiMoO4 nanorods. Subsequently, utilizing the electrodeposition method with a solution rich in Ni²⁺ and Fe³⁺ as the electrolyte, we delicately tuned the process to identify the optimal deposition time, achieving a uniform coating of NiFe LDH on the surface of the P-doped NiMoO4 nanorods. This led to the construction of a three-dimensional core-shell structured NiFe LDH@P-NiMoO4 composite material. To validate the performance of this composite, we conducted thorough structural characterization and electrochemical oxygen evolution reaction (OER) performance tests. The experimental results revealed that in a 1 M KOH electrolyte environment, when the current density reached 100 mA cm⁻², the composite exhibited exceptionally superior OER performance, with an overpotential of merely 267 mV and a Tafel slope as low as 93 mV dec⁻¹, firmly demonstrating its remarkable catalytic efficiency. Furthermore, the composite displayed good stability and durability during prolonged testing, providing a solid foundation for its practical application. In summary, this work not only paves a new way for the preparation of high-performance non-precious metal OER electrocatalysts but also provides robust support for the realization of efficient and stable energy conversion and storage technologies.

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.

Manipulating the Electronic Properties of an Fe Single Atom Catalyst via Secondary Coordination Sphere Engineering to Provide Enhanced Oxygen Electrocatalytic Activity in Zinc-Air Batteries.

Oxygen reduction and evolution reactions are two key processes in electrochemical energy conversion technologies. Synthesis of nonprecious metal, carbon-based electrocatalysts with high oxygen bifunctional activity and stability is a crucial, yet challenging step to achieving electrochemical energy conversion. Here, an approach to address this issue: synthesis of an atomically dispersed Fe electrocatalyst (Fe1/NCP) over a porous, defect-containing nitrogen-doped carbon support, is described. Through incorporation of a phosphorus atom into the second coordination sphere of iron, the activity and durability boundaries of this catalyst are pushed to an unprecedented level in alkaline environments, such as those found in a zinc-air battery. The rationale is to delicately incorporate P heteroatoms and defects close to the central metal sites (FeN4P1-OH) in order to break the local symmetry of the electronic distribution. This enables suitable binding strength with oxygenated intermediates. In situ characterizations and theoretical studies demonstrate that these synergetic interactions are responsible for high bifunctional activity and stability. These intrinsic advantages of Fe1/NCP enable a potential gap of a mere 0.65V and a high power density of 263.8mWcm-2 when incorporated into a zinc-air battery. These findings underscore the importance of design principles to access high-performance electrocatalysts for green energy technologies.

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.

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.

Construction of high‐loading WO3‐x sub‐nanometer clusters via orderly‐anchored top–down strategy boost acidic hydrogen evolution

AbstractExploring a simple, rapid, and scalable synthesis method for the synthesis of high loading nonprecious metal sub‐nanometer clusters (SNCs) electrocatalysts is one of the most promising endeavors today. Herein, an orderly‐anchored top–down strategy is proposed for fabricating a new type of high loading WO3‐x SNCs on O‐functional group‐modified Ketjen black (WO3‐x‐C(O)) to balance the high loading (49.29 wt.%) and sub‐nanometer size. By optimizing the vacancy number, WO2.71‐C(O) has extremely large electrochemically active surface area (402 m2 g−1) and high turnover frequency value of 1.722 s−1 at −50 mV (vs. reversible hydrogen electrode). The overpotential of WO2.71‐C(O) reaches 22 mV at a current density of 10 mA cm−2, which is significantly better than the commercial Pt/C level (32 mV), achieving a breakthrough in the hydrogen evolution reaction (HER) catalytic activity of nonprecious metals in acidic environment. Theoretical calculations and in situ characterization show that this material allows for the enrichment of reactants (H*) and the optimization of intermediate adsorption, which leads to the enhancement of acidic HER catalytic activity.

Bimetallic Sulfur-Doped Nickel-Cobalt Selenides as Efficient Bifunctional Electrocatalysts for the Complete Decomposition of Water.

The creation and enhancement of non-precious metal bifunctional catalysts with superior stability and stabilizing activity is necessary to achieve water splitting in alkaline media. The paper presents a method for preparing nickel-cobalt bimetallic selenides (NiCo-Sex/CF) using a combination of hydrothermal and high-temperature selenization techniques. NiCo-Sex/CF shows great potential as a catalyst for water separation. The catalyst's electronic structure and active centre can be modified by double doping with sulfur and selenium, resulting in increased selectivity and activity under varying reaction conditions. This method also offers the benefits of a simple preparation process and applicability to a wide range of catalytic reactions. Experimental results demonstrate that an overpotential of 194 mV produces a current density of 10 mA cm-2 when using this electrocatalyst as an OER catalyst. When used as a HER catalyst, the electrocatalyst required an overpotential of only 76 mV to generate a current density of 10 mA cm-2.Furthermore, a voltage of 1.5 V can drive the overall decomposition of water to achieve a current density of 10 mA cm-2. This study highlights the potential of sulfur-selenide double-doped catalysts for both scientific research and practical applications.

3D hierarchical nanostructured NiCo-LDH/Cu electrode for efficient alkaline hydrogen evolution

The development of an efficient and cost-effective electrocatalyst for the Hydrogen Evolution Reaction (HER) that can be widely applied in industrial settings poses a multifaceted challenge. This research involved fabricating a NiCo-LDH/Cu electrode as a self-supported catalyst for hydrogen evolution on nickel foam using a solvothermal method and constant potential electrodeposition. In comparison to the NiCu electrocatalyst produced through a single-step electrodeposition, the NiCo-LDH/Cu hydrogen evolution electrode prepared via this combined approach exhibited significant electrocatalytic performance for HER in an alkaline electrolyte. The NiCo-LDH/Cu catalytic electrode requires only an overpotential of 78.0 mV to achieve a current density of 10 mA·cm−2 in 1 M KOH. The current density required to catalyze the hydrogenation reaction is reduced by 64 % compared to pure nickel foam. This reduction accelerates the hydrogenation catalytic reaction and enhances electrochemical stability. The remarkable HER efficiency of the NiCo-LDH/Cu catalytic electrode primarily stems from the increased active surface area facilitated by the LDH structure and the synergistic impact generated during the NiCu co-deposition process. This work shows an economical and practical method for developing efficient non-precious metal catalytic electrodes.

NiFe-spinel oxides with nitrogen-doped carbon quantum dots for enhanced oxygen evolution activity

Designing efficient and stable electro-catalysts for non-precious metal oxygen evolution reactions (OER) is critical to solve the bottleneck of water splitting. The NiFe2O4/NCQDs composite electrode was fabricated by combining nitrogen doped carbon quantum dots (NCQDs) with NiFe2O4 spinel via a hydrothermal method, which showed brilliant OER catalytic performance by modifying on nickel foams (NF). The composites had petal-like structures, and the NiFe2O4 was epitaxially grown on the NF substrates with exposed sites, resulting in enhanced electron transport. The fluorescence quenching of NCQDs was accompanied by binding NCQDs with NiFe2O4, which indicated the energy barrier was greatly reduced during the electron transport as well as electro-catalysis. The higher intrinsic charge transfer was achieved, and the doping combination having a higher conductivity was confirmed. The electrochemical activity of NiFe2O4/NCQDs electrode in OER reaction was evaluated under alkaline conditions. The addition of NCQDs effectively enhanced the OER activity, and over-potentials were decreased from 330 mV to 270 mV at 10 mA cm−2 with Tafel slope lower (66 mV/dec) than counterparts. The NiFe2O4/NCQDs displayed long-term catalytic stability at 1.47 V. Therefore, a facile method for preparing NiFe2O4/NCQDs was developed which had characteristics of low cost, simple process and excellent OER activity.

Core-shell like rGO coated Co9S8 hollow dodecahedron for enhanced oxygen evolution reaction

The development of low-cost, high-activity, high-durability non-precious metal OER electrocatalysts is still the most critical bottleneck for the preparation of clean-energy by water splitting. In this thesis, the Co9S8@rGO heterogeneous interface was constructed to optimize the electron transport pathway and enhance the active site to improve the OER activity. The ZIF-67 dodecahedron was used as a template to prepare Co9S8 with a hollow dodecahedron structure using the hydrothermal method and annealing treatment to shorten the charge transport path and increase its specific surface area. Subsequently, a protective shell layer of rGO with good conductivity and stability was wrapped around the Co9S8 catalyst core by the construction of a Co9S8@rGO core-shell heterostructure. It was found that the 30 % Co9S8@rGO core-shell heterostructure not only reduced the overpotential (190 mV at 10 mA cm−2) and tafel slope (66.48 mV dec−1) but also improved the stability compared to Co9S8. The density of states and the Gibbs free energy of HO*, O* and HOO* intermediates of Co9S8@rGO were investigated by first-principles theoretical calculations according to density functional theory (DFT). The DFT calculation results showed that the Gibbs free energy (ΔG30) of Co9S8@rGO core-shell heterostructure was lower than that of Co9S8 in the rate-control step, which leaded to the decrease of overpotential and was beneficial to the OER reaction.

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.

Mn/CeO2 contains enriched surface lewis acid sites and pore structures accelerated catalytic oxidation of propane at low temperature

The development of highly efficient non-precious metal catalysts for the low-temperature catalytic oxidation of volatile organic compounds (VOCs) is a critical imperative in VOCs control. In this study, a series of highly active CeMnOx catalysts with Mn-doped CeO2 were investigated. The catalysts (WHSV=30,000 mL g−1 h−1) exhibited the highest catalytic propane oxidation activity (T90 = 230 °C) and excellent stability over 600 h, When the Mn:Ce ratio was 2.5. The introduction of Mn doping resulted in modifications to the pore structure of CeO2, leading to an increase in specific surface area and enhanced gas transfer kinetics. Additionally, it induced surface electronic defects and elevated the concentration of acidic sites, thereby facilitating the adsorption and activation of propane. Consequently, these improvements contributed to an enhanced catalytic performance of the catalyst. The in-situ DRIFTS infrared spectra revealed that Mn doping reduced the activation energy of the reaction and facilitated the conversion of acetone groups as well as decomposition of carboxylic acid groups.