Alloy Electrocatalysts Research Articles

Hydrogen-Rich Pyrolysis from Ni-Fe Heterometallic Schiff Base Centrosymmetric Cluster Facilitates NiFe Alloy for Efficient OER Electrocatalysts.

Binary metal nickel-iron alloys have been proven to have great potential in oxygen evolution reaction (OER) electrocatalysis, but there are still certain challenges in how to construct more efficient nickel-iron alloy electrocatalysts and maximize their own advantages. In this work, a heterometallic nickel-iron cluster (L=C64 H66 Fe4 N8 Ni2 O19 ) of Schiff base (LH3 =2-amino-1,3-propanediol salicylaldehyde) is designed as a precursor to explore its behavior in the pyrolysis process under inert atmosphere. The combination of TG-MS, morphology, and X-ray characterization techniques shows that the Schiff base ligands in the heterometallic clusters produces a strong reductive atmosphere during pyrolysis, which enable the two 3d metals Ni and Fe to form NiFe alloys. Moreover, Fe2 O3 /Fe0.64 Ni0.36 @Cs carbon nanomaterials are formed, in which Fe2 O3 /Fe0.64 Ni0.36 is the potential active material for OER. It is also found that the centrosymmetric structure of the heterometallic Schiff base precursor is potentially related to the formation of the Fe2 O3 /Fe0.64 Ni0.36 alloy@carbon structures. The Fe2 O3 /Fe0.64 Ni0.36 @C-800 provides 274mV overpotential in 1m KOH solution at 10mAcm-2 in OER. This work provides an effective basis for further research on Schiff base bimetallic doping-derived carbon nanomaterials as excellent OER electrocatalysts.

Metal-organic framework derived FeNi alloy nanoparticles embedded in N-doped porous carbon as high-performance bifunctional air-cathode catalysts for rechargeable zinc-air battery

Developing efficient and durable bifunctional air–cathode catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is one of the key efforts promoting the practical rechargeable zinc-air batteries (ZABs). In this paper, high-performance bifunctional air–cathode catalysts by a two-step strategy: atomically dispersed Ni on N-doped carbon is first derived from MOF to form uniformly dispersed NiNC, which are pyrolyzed together with Fe source at different high-temperatures to form FeNi@NC-T (T = 800, 900, and 1000 °C) catalysts. The as-synthesized non-noble metal FeNi@NC-900 catalyst exhibits a considerably small potential gap (ΔE) of 0.72 V between ORR and OER, which is as the same as commercial noble metal Pt/C + Ir black mixed catalyst. The performance of the ZABs using FeNi@NC-900 as the air–cathode catalyst displays a power density of 119 mW·cm−2 and a specific capacity of 830.1 mAh·g−1, which is superior to that of Pt/C + Ir black mixed catalyst. This work provides a guideline for designing alloy electrocatalysts with uniform size and nanoparticle distribution for metal-air batteries with bifunctional air-cathodes.

Development of a Novel Pt3V Alloy Electrocatalyst for Highly Efficient and Durable Industrial Hydrogen Evolution Reaction in Acid Environment

AbstractAlloying platinum with early transition metals is a promising approach to optimize the adsorption behaviors of catalysts. Nevertheless, the large negative redox potential between early transition metals and Pt hinders the fabrication of such alloys. Herein, a strategy combining the thermal shock technique with electrochemical activation to prepare Pt3V alloy as a hydrogen evolution reaction catalyst is reported for the first time. Electrochemical tests show that the as‐prepared catalyst exhibits exceptional catalytic activity and durability in 0.5 m H2SO4, surpassing the state‐of‐the‐art 20 wt.% Pt/C. The catalyst can maintain its activity after 100 h tests without evident decay under the current density of 500 mA cm−2. Theoretical calculations demonstrate that the optimized hydrogen absorption and high vacancy formation energy of Pt3V contributes to the enhanced electrocatalytic activity and stability. This work may spur future research for other Pt‐based early transition metal alloy catalysts for electrocatalysis.

High-performance rechargeable metal–air batteries enabled by efficient charge transport in multielement random alloy electrocatalyst

The integration of bifunctionally active sites of multielement random alloy catalysts with other metal oxide electrocatalysts is a promising strategy for efficient electrochemical reactions. In this study, a novel combination of virtual crystal approximation and hydrothermal synthesis was used to investigate the composition-dependent structure and electrical property in a Ag1−xNix catalyst. The combination showed that a hexagonal closed-packed structure of Ag1−xNix with a compositional ratio of 6:4 (Ag:Ni) had electrical conductivity of ∼2 × 107 S∙cm−1 and an ionization potential of − 5.4 eV. Furthermore, the bifunctional oxygen electrocatalytic efficiencies of Ag0.6Ni0.4 were improved by forming a heterointerface with the CoNb2O6 electrocatalyst, resulting in a discharge-charge voltage gap of 0.81 V over 587 h, peak power density of 178.9 mW∙cm−2, and specific capacity of 806.8 mA∙h∙g−1 in a zinc–air battery. This approach was applied to pouch-type zinc–air batteries, resulting in long-term stability of over 158.6 h at 10 mA∙cm−2.

Ordered PtCoFe Ternary Alloy Electrocatalyst Derived from Pre-Synthesized CoFe Hydroxide for Oxygen Reduction Reaction

Ordered PtCoFe Ternary Alloy Electrocatalyst Derived from Pre-Synthesized CoFe Hydroxide for Oxygen Reduction Reaction

Facile electrodeposition synthesis and super performance of nano-porous Ni-Fe-Cu-Co-W high entropy alloy electrocatalyst

Establishing efficient nano-porous electrocatalysts for facilitating electron transfer is a one of the useful ways for enhance water splitting. Herein, Ni-Fe-Cu-Co-W high entropy alloy (NFCCW-HEA) electrocatalysts on the iron sheet substrate have been successfully prepared by a simple and efficient one-step electrodeposition method. High entropy alloys have a variety of active sites and unique atomic scale synergies, which makes the catalyst have good catalytic performance and stability. Meanwhile, the HEA coating like cauliflower by electrodeposition can provide more attachment sites, and significantly upgrade the OER catalytic activity. NFCCW-HEA catalysts exhibit an excellent overpotential of 247.3 mV under the current density of 10 mA·cm−2, and a low Tafel slope of 62.9 mV dec−1. The electrocatalyst shows long term stability of electrolysis for over 24 h in 1 mol·L−1 KOH alkaline solution, which shows good stability. We expect to provide a new idea for the preparation of nano porous high entropy alloy electrocatalysts by one-step electrodeposition technology.

Cl modulation on boron-rich carbon embedded with NiFe alloys for efficient oxygen evolution reaction

The rational design of cost-effective oxygen evolution reaction (OER) electrocatalysts is important for the future global energy supply but remains a formidable challenge. Herein, Cl-doped boron-rich carbon nanocomposites embedded with NiFe alloys (FexNiy@ClBC) were constructed via a facile mechanochemical-assisted strategy for use as an OER electrocatalyst. Combination of the unique Cl-doped boron-rich carbon species with the NiFe alloy optimized the electronic structure and surface properties. Meanwhile, Density flooding theory (DFT) calculations confirmed that the Fe1Ni2@ClBC catalyst weakened the strong adsorption of *O and *OOH intermediates due to the introduction of Cl, which reduced the ΔGmax of the OER process and led to a more favorable reaction kinetics. As a result, this catalyst exhibited a remarkable OER performance with a low overpotential (259 mV at 10 mA cm−2, 296 mV at 50 mA cm−2) and a small Tafel slope (49 mV dec−1). The Fe1Ni2@ClBC catalyst exhibited a considerable stability under harsh alkaline conditions for over 40 h because of its external highly robust porous carbon shell. This work contributes to the understanding of nonmetallic heteroatom-doped carbon materials and should inspire the design of low-cost alloy electrocatalysts.

Self-Circulating Adsorption–Desorption Structure of Non-Noble High-Entropy Alloy Electrocatalyst Facilitates Efficient Water Splitting

Electrochemical splitting of water is an efficient pathway to the energy revolution. The challenge of balancing excellent electrochemical performance with the high cost of existing hydrogen evolution reaction catalysts has forced the development of efficient non-noble metal catalysts. Here, we prepared a FeCoNiWMo high-entropy alloy having a rhomboidal structure with atomic random occupancy. The unique atomic random occupation facilitates the formation of a self-circulating adsorption–desorption structure with fast electron transport inside, which significantly promotes water splitting. Especially, the overpotential of the catalyst at a current density of 10 mA cm–2 is only 35 mV under alkaline conditions. This work emphasizes the importance of coordinating a self-circulating proton transport structure and a disordered high-entropy state to manipulate the adsorption energy of an intermediate for developing high-performance electrocatalysts.

Carbon dots regulate the multiple-proton-electron catalytic process and switch carbon dioxide reduction to hydrogen evolution reaction of PdCu alloy electrocatalyst

Electrocatalytic CO2 reduction reaction (ECO2RR) is a typical small molecule conversion reaction, which involves multiple-proton-electron coupling processes. As a typical competitive reaction, hydrogen evolution reaction (HER) competes with ECO2RR for protons, thus increasing the diversity of reaction paths. In this work, PdCu alloy is an effective electrocatalyst for ECO2RR. After the combination of carbon dots (CDs) with PdCu alloy, the highly efficient ECO2RR on the surfaces of PdCu alloy turns to HER for the first time. The strong adsorption of electrons and protons by CDs altered the reaction path on the PdCu for ECO2RR, as confirmed by a series of characterizations and transient photo-induced voltage tests, leading to the switch of ECO2RR to HER. This work verifies the important role of CDs in the regulation of electron transfer and proton, realizes the interference of the multi-proton and multi-electron catalytic processes on the well-defined active center (or one active center), and gives us a new insight to design the reaction paths.

Nanosized amorphous nickel-boron alloy electrocatalysts for hydrogen evolution reaction under alkaline conditions

Hydrogen production from electrolyzed water driven by sustainable energy is an effective way to achieve the hydrogen economy with zero carbon emission. Alkaline electrocatalytic hydrogen evolution reaction (HER) is one of the main energy transforming processes in the field of electrolytic water technology. The development of active and cost-effective nonprecious catalytic electrodes is of great importance to alkaline hydrogen evolution reaction. Amorphous nanosized nickel-boron alloy particles (NiB-COS) have been obtained by using chitosan oligosaccharides (COS) as a stabilizer via chemical reduction method. The as-prepared electrocatalysts have been used for the hydrogen evolution reaction (HER). The electrocatalysts have been characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma analysis (ICP) and X-ray photoelectron spectroscopy (XPS). NiB-COS displays a significant increase in hydrogen evolution reaction properties in alkaline media, affording low overpotentials of 49.4 mV at 10 mA/cm2 and 15.1 mV onset overpotential for the hydrogen evolution reaction. Tafel slope of NiB-COS is 86.1 mV/dec. Remarkably, the formation of a nickel-boron alloyed phase and the decrease of particle size are helpful to improve HER activity of NiB-COS. The experimental data indicated that the NiB-COS showed excellent long-term stability as a very active electrocatalyst.

Novel Mechanically-Alloyed Cu–La–P Ternary Alloy Electrocatalysts for the Alkaline Hydrogen Evolution Reaction

Transition metal phosphides, such as Cu3P, are of research interest as hydrogen evolution electrocatalysts due to a combination of good intrinsic activity and good stability. Rare earth-transition metal alloying is known to improve electrocatalytic performance, especially by the formation of intermetallic phases. Current transition metal phosphide electrocatalyst manufacturing methods are not capable of forming these intermetallic phases. Mechanical alloying is a promising technique to synthesize these intermetallic phases. Alloy powders of Cu3P, Cu19La5P12, and a novel multi-phase Cu74La4P22 composition were prepared using mechanical alloying and evaluated as electrocatalysts for the alkaline hydrogen evolution reaction on a geometric and intrinsic area basis. On an intrinsic basis, the novel Cu–La–P composition demonstrated excellent Tafel performance of 69.4 mV dec−1. Tafel slope, exchange current density, and overpotential data demonstrated the importance of spillover effects in multiphase Cu3P/Cu19La5P12 surface structures. These results suggest that Cu–La–P alloys are promising potential catalysts for electrochemical hydrogen production, and mechanical alloying of rare earth elements is an effective technique for improving the electrochemical performance of transition metal phosphides.

Accurate and efficient machine learning models for predicting hydrogen evolution reaction catalysts based on structural and electronic feature engineering in alloys.

Predictive materials design of high-performance alloy electrocatalysts is a grand challenge in hydrogen production via water electrolysis. The vast combinatorial space of element substitutions in alloy electrocatalysts offers a wealth of candidate materials, but presents a significant challenge in terms of experimental and computational exploration of all possible options. Recent scientific and technological developments in machine learning (ML) have offered a new opportunity to accelerate such electrocatalyst materials design. Herein, by incorporating both the electronic and structural properties of alloys, we are able to construct accurate and efficient ML models and predict high-performance alloy catalysts for the hydrogen evolution reaction (HER). We have identified the light gradient boosting (LGB) algorithm as the best-performed method, with an excellent coefficient of determination (R2) value reaching 0.921 and the corresponding root-mean-square error (RMSE) being 0.224 eV. The average marginal contributions of alloy features towards ΔGH* values are estimated to determine the importance of various features during the prediction processes. Our results indicate that both the electronic properties of constituent elements and the structural adsorption site features play the most critical roles in the ΔGH* prediction. Furthermore, 84 potential alloys with |ΔGH*| values less than 0.1 eV are successfully screened out of 2290 candidates selected from the Material Project (MP) database. It is reasonable to expect that the ML models with structural and electronic feature engineering developed in this work would provide new insights in future electrocatalyst developments for the HER and other heterogeneous reactions.

Recent developments in Pt-based alloy nanoparticles for oxygen reduction reaction in fuel cells

The significance of proton exchange membrane fuel cells (PEMFs) in economic recovery and climate action initiatives following a pandemic is growing. PEM fuel cells depend on precious-metal catalysts (often Pt or Pt-based alloys) to catalyze the reactions occurring at the electrodes. This is especially true for the cathodic oxygen reduction reaction (ORR), which is slow, represents a large source of energy loss, and brings the overall efficiency of fuel cells down. The performance, cost, and durability of these Pt-based catalysts for ORR hinder their widespread commercial application. As a realistic technique for decreasing Pt usage and related costs, researchers have concentrated intensively in recent years on producing more active and stable Pt-based alloy electrocatalysts. This review article mainly focuses on recent literature of Pt-based alloy electrocatalysts for ORR, especially the effect of nanoparticles (NPs) size, and shape and, therefore, the activity and stability of the generated electrocatalysts. The ORR activity and stability of Pt-based alloys such as Pt-Ni, Pt-Cu, and Pt-Fe, as well as other nano electrocatalysts, will be reviewed along with various synthetic approaches.

Understanding the evolution of catalytically active multi-metal sites in a bifunctional high-entropy alloy electrocatalyst for zinc–air battery application

Rechargeable zinc-air battery operations in an aqueous alkaline electrolyte were studied using a novel FCC crystalline high-entropy alloy CCMNF (Co, Cu, Mn, Ni, Fe) as a bifunctional electrocatalyst at the air electrode.

Recent progress in the development of Platinum-based electrocatalysts for the oxidation of ethanol in fuel cells

Humans have an ever-increasing and ever-insatiable need for energy. The world's energy demands are currently being met by burning nonrenewable fossil fuels. Recurring challenges for civilization include developing dynamic energy cradles for a prosperous society to lessen fossil fuel depletion and environmental issues. The energy gap in the modern era can only be closed by the discovery of vast quantities of non-conventional resources. In place of dirty and inefficient fossil fuels, fuel cells provide a powerful and environmentally friendly alternative. In the realm of fuel cells, the direct ethanol fuel cell (DEFC) has garnered a lot of attention because it is a renewable fuel, easy to handle, and safe to use. High catalytic capabilities and durability make Pt-based electrocatalysts very promising. However, widespread commercial use has been hampered by their expensive price, poor stability, and Pt shortage. The keys to DEFC's practical uses are increasing the activity and durability of Pt-based electrocatalysts while decreasing the Pt content. This article will provide a summary of the most recent results about the development of Pt-based alloy electrocatalysts for ethanol oxidation. In addition, the most significant technological challenges are recognized, as well as prospective future study fields to solve these difficulties in order to pave the way for more research and development leading to practical implementation.

Designing mixed-metal electrocatalyst systems for photoelectrochemical dinitrogen activation.

Efficient artificial photosynthesis systems are currently realized as catalyst- and surface-functionalized photovoltaic tandem-and triple-junction devices, enabling photoelectrochemical (PEC) water oxidation while simultaneously recycling CO2 and generating hydrogen as a solar fuel for storable renewable energy. Although PEC systems also bear advantages for the activation of dinitrogen - such as a high system tunability with respect to the electrocatalyst integration and a directly controllable electron flux to the anchoring catalyst through the adjustability of incoming irradiation - only a few PEC devices have been developed and investigated for this purpose. We have developed a series of photoelectrodeposition procedures to deposit mixed-metal electrocatalyst nanostructures directly on the semiconductor surface for light-assisted dinitrogen activation. These electrocatalyst compositions containing Co, Mo and Ru in different atomic ratios follow previously made recommendations of metal compositions for dinitrogen reduction and exhibit different physical properties. XPS studies of the photoelectrode surfaces reveal that our electrocatalyst films are to a large degree nitrogen-free after their fabrication, which is generally difficult to achieve with traditional magnetron sputtering or e-beam evaporation techniques. Initial chronoamperometric measurements of the p-InP photoelectrode coated with the Co-Mo alloy electrocatalyst show higher photocurrent densities in the presence of N2(g) than in the presence of Ar at -0.09 V vs. RHE. Indications of successful dinitrogen activation have also been found in consecutive XPS studies, where both N 1s and Mo 3d spectra reveal evidence of nitrogen-metal interactions.

Electrocatalytic CO 2 Reduction over Bimetallic Bi-Based Catalysts: A Review

Electrocatalytic CO ₂ Reduction over Bimetallic Bi-Based Catalysts: A Review

A critical review of research progress for metal alloy materials in hydrogen evolution and oxygen evolution reaction.

Hydrogen produced by electrolyzing water has attracted extensive attention as an effective way to generate and store new energy by using renewable energy. Electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were the core reactions in the process of hydrogen production by water electrolysis, however, due to the low efficiency of the electrolytic device caused by its slow kinetic reaction and the dependence on noble metal catalysts (platinum and iridium/ruthenium (oxide)), which limited its wide application. The preparation of high-efficiency catalysts with high catalytic activity, stability, low cost and scalability played a vital role in promoting the development of hydrogen production technology from electrolytic water and has become a current research hotspot. Metal alloy catalysts have been widely studied as high-efficiency electrocatalysts. This study introduced and analyzed the mechanism and application of metal alloy catalyst in hydrogen and oxygen evolution reaction, summarized and discussed the progress in the design, preparation and application of metal alloy electrocatalysts. Finally, the strategy and prospect of new high-efficiency electrocatalysts were proposed.

A novel MOF-derived strategy to construct Cu-doped CeO2 supported PdCu alloy electrocatalysts for hydrogen evolution reaction

Hydrogen evolution reactions (HER) via water splitting is of significance for electricity-to-fuel conversion. The pursuits of rationally design and facile synthesis method for efficient HER catalysts have long been a subject of interest. In this work, a bimetallic MOF-derived strategy was constructed to realize doping and alloying of transition metal in parallel and Pd-CuCeOx catalyst was prepared, in which Cu served as doping element in CeO2 and secondary metal in Pd-Cu alloy. For the as-synthesized Pd-CuCeOx, an overpotential of 109 mV is needed to reach a current density of 10 mA cm−2 with a Tafel slope of only 30.9 mV dec−1. With the low content of precious metal, Pd-CuCeOx exhibited a high TOF value of 6.99 s−1, which is about 3.5 times higher than that of commercial Pt/C. The improved HER performance is attributed to the d-band structure modified by alloying and the enhanced electronic coupling caused by doping.

Magnetic-field-regulated Ni-Fe-Mo ternary alloy electrocatalysts with enduring spin polarization enhanced oxygen evolution reaction

The oxygen evolution reaction (OER) constrains the efficiency of water splitting. The catalytic activity of electrocatalysts is mostly determined by the electronic structure, which is expressed as the electron transfer property and the reactant adsorption–desorption capacity. Ferromagnetic electrocatalysts exhibit promising applications in OER. However, an external magnetic field is indispensable for the electron spin polarization of ferromagnetic materials. Here, Ni-Fe-Mo ternary alloy nanowire electrocatalysts were prepared via a magnetic field-assisted self-assembly method in an aqueous-solution system at a mild temperature (65 °C). These Ni-Fe-Mo ternary alloy electrodes feature a spin polarization-dependent OER catalytic performance, which is attributed to ferromagnetic regulation. Ni0.8Fe0.15Mo0.05 possesses the maximum ferromagnetism compared to other electrodes (Ni0.8Mo0.2 and Ni0.8Fe0.2) and improved substantially OER activity. The regulated OER activity is assigned to the favorable adsorption of oxygen-containing intermediates (OH*) due to Ni-Fe-Mo composition-dependent, and the accelerated kinetics of OER with enduring spin polarization. The Ni-Fe-Mo ternary alloy nanowires with higher magnetic properties contribute to in situ spin polarization at the surface. This magnetic field-assisted synthesis approach provides a new strategy to realize electrodes with enduring spin polarized.