Bimetallic Electrocatalysts Research Articles

Efficient biobased carboxylic acids synthesis by synergistic electrocatalysis of multi-active sites on bimetallic Cu-Co oxide/oxyhydroxide

In this study, we reported a low-cost and highly efficient bimetallic Cu-Co oxide/oxyhydroxide electrocatalyst (CuOCoOOH) for synthesizing bio-based carboxylic acids. The incorporation of Cu in CuOCoOOH enhanced substrate absorption, defect construction, and the formation of high valence active species, thus significantly improving the electrooxidation performance of the catalyst. The electrooxidation of 5-hydroxymethylfurfural with CuOCoOOH exhibited an excellent yield (98%) of 2,5-furandicarboxylic acid with a Faradaic efficiency of 98%. Density functional theory calculations revealed the effectiveness of substrate adsorption ability and oxygen vacancy formation of CuOCoOOH in improving the electrooxidation performance. Additionally, 12 carboxylic acids were successfully produced from bio-based alcohols/aldehydes with excellent yields of 96.4–99%. In summary, non-noble bimetallic electrocatalyst was successfully developed for synthesizing value-added bio-based platform chemicals in practical. This study provides a tandem valorization route of electrocatalysis and biorefinery toward a more carbon-neutral and sustainable industry.

A pyrolysis-free Ni/Fe bimetallic electrocatalyst for overall water splitting

Catalysts capable of electrochemical overall water splitting in acidic, neutral, and alkaline solution are important materials. This work develops bifunctional catalysts with single atom active sites through a pyrolysis-free route. Starting with a conjugated framework containing Fe sites, the addition of Ni atoms is used to weaken the adsorption of electrochemically generated intermediates, thus leading to more optimized energy level sand enhanced catalytic performance. The pyrolysis-free synthesis also ensured the formation of well-defined active sites within the framework structure, providing ideal platforms to understand the catalytic processes. The as-prepared catalyst exhibits efficient catalytic capability for electrochemical water splitting in both acidic and alkaline electrolytes. At a current density of 10 mA cm−2, the overpotential for hydrogen evolution and oxygen evolution is 23/201 mV and 42/194 mV in 0.5 M H2SO4 and 1 M KOH, respectively. Our work not only develops a route towards efficient catalysts applicable across a wide range of pH values, it also provides a successful showcase of a model catalyst for in-depth mechanistic insight into electrochemical water splitting.

C‐Bound or O‐Bound Surface: Which One Boosts Electrocatalytic Urea Synthesis?

AbstractThe electrocatalytic C−N coupling from carbon dioxide and nitrate under ambient conditions is kind of sustainable and promising alternative method for urea synthesis. To date, the influence of catalyst surface properties on molecular adsorption configuration and electrocatalytic urea synthesis activity is unclear. In this work, we proposed that the urea synthesis activity is closely linked with the localized surface charge on bimetallic electrocatalysts, it is found that a negatively charged surface induces C‐bound path and boosts urea synthesis. The urea yield rate can reach 13.1 mmol g−1 h−1 on negatively charged Cu97In3‐C, which is about 13 times that of positively charged Cu30In70‐C counterpart with O‐bound surface. This conclusion also applies to Cu−Bi and Cu−Sn systems. The molecular modification shifts the surface of Cu97In3‐C to positively charged state, which leads to a sharp decline in urea synthesis performance. We demonstrated that the C‐bound surface is more favorable than O‐bound one to boost electrocatalytic urea synthesis.

C-Bound or O-Bound Surface: Which One Boosts Electrocatalytic Urea Synthesis?

The electrocatalytic C-N coupling from carbon dioxide and nitrate under ambient conditions is kind of sustainable and promising alternative method for urea synthesis. To date, the influence of catalyst surface properties on molecular adsorption configuration and electrocatalytic urea synthesis activity is unclear. In this work, we proposed that the urea synthesis activity is closely linked with the localized surface charge on bimetallic electrocatalysts, it is found that a negatively charged surface induces C-bound path and boosts urea synthesis. The urea yield rate can reach 13.1 mmol g-1 h-1 on negatively charged Cu97 In3 -C, which is about 13 times that of positively charged Cu30 In70 -C counterpart with O-bound surface. This conclusion also applies to Cu-Bi and Cu-Sn systems. The molecular modification shifts the surface of Cu97 In3 -C to positively charged state, which leads to a sharp decline in urea synthesis performance. We demonstrated that the C-bound surface is more favorable than O-bound one to boost electrocatalytic urea synthesis.

Polysulfide-Induced Synthesis of Coral-Like MoS2/NiS2 Nanostructures for Overall Water Splitting

The development of multifunctional electrocatalysts with rich resources, excellent performance, and stability is necessary for water splitting to achieve sustainable hydrogen and oxygen production. Herein, we report the preparation of a bifunctional coral-like nanostructured electrocatalyst (p-MoS2/NiS2) by in situ vulcanization of polymeric sulfur with a MoO3/Ni as the precursor. It is exciting that the whole preparation process of the electrocatalyst can be completed in a few hours. The as-fabricated multimetallic sulfide not only exhibits well-defined heterointerfaces and the defect-rich two-dimensional (2D) nanoconfiguration with high conductivity to overcome the poor hydrogen evolution reaction (HER) activity, but also promotes the formation of the 1T phase. The obtained p-MoS2/NiS2 nanostructures exhibit low overpotentials of −115 mV at −10 mA cm–2 and 337 mV at 100 mA cm–2 toward the HER and oxygen evolution reaction (OER), respectively, which surpass most of the previously reported bimetallic sulfide-based electrocatalysts. Benefiting from the stability of the hierarchical heterostructure and the coupling effect between the inner layer of NiS2 and outer layers of MoS2, the p-MoS2/NiS2 catalyst is endowed with high activity for water splitting. It can be used as a bifunctional electrocatalyst for water splitting with a cell voltage of 1.51 V at a current density of 10 mA cm–2. Overall, this work proposes a simple in situ vulcanization method to synthesize MoS2, which expands the interlayer spacing and realizes the coexistence of a metastable structure and metal doping.

Regulating the Synergistic Effect in Bimetallic Two-Dimensional Polymer Oxygen Evolution Reaction Catalysts by Adjusting the Coupling Strength Between Metal Centers.

Bimetallic electrocatalysts with its superior performance has a broad application prospect in oxygen evolution reaction (OER), but the fundamental understanding of the mechanism of synergistic effect is still limited since there lacks a practical way to decouple the influence factors on the intrinsic activity of active sites from others. Herein, a series of bimetallic Co-Ni two-dimensional polymer (2DP) model OER catalysts with well-defined architecture, monolayer characteristic, were designed and synthesized to explore the influence of the coupling strength between metal centers on OER performance. The coupling strength was regulated by adjusting the spacing between metal centers or the conjugation degree of bridge skeleton. Among the examined 2DPs, CoTAPP-Ni-MF-2DP, which has the strongest coupling strength between metal centers exhibited the best OER performance. These model systems can help to explore the precise structure-performance relationships, which is important for the rational catalyst design at the atomic/molecular levels.

Study on the Structure vs Activity of Designed Non-Precious Metal electrocatalysts for CO2 Conversion

This work investigates Cu and Cu-Sn nanocatalysts with controlled composition and morphology for the electrochemical CO2 reduction reaction to value-added chemicals, showing that bimetallic materials possess active sites with increased specific activity toward activation and reduction of CO2 compared to monometallic ones. While Cu showed high selectivity for the competitive hydrogen evolution reaction, bimetallic Cu-Sn electrocatalysts were selective towards CO and formates. Nanoparticles were prepared via a straightforward chemical process, leading to small, well-define and crystalline nanoparticles, either mono or bimetallic, where Cu and Sn precursors are blended in one step to achieve alloyed or core–shell structures.

Nanostructured NiFe (oxy)hydroxide fabricated on nickel foams by laser-induced water plasma for enhanced alkaline oxygen evolution reaction

Hydrogen production from water electrolysis is hindered by the sluggish reaction kinetics, especially the anodic oxygen evolution reaction (OER). Dynamic surface structures and high valence metal sites are usually required in the development of highly efficient OER electrocatalysts, which are hardly realized using conventional preparation method. Here, we propose a novel and facile method to fabricate nickel-based OER electrocatalysts with non-thermal laser-induced water plasma. Using nickel foams (NFs) as the initial substrates, the NFs or Fe-doped FeOx/NFs treated with laser-induced water plasma own abundant Ni(Fe) hydroxide and oxyhydroxide nanostructures,labeled as Ni(Fe) (oxy)hydroxide thereafter, formed on the skeleton of NFs, which are characterized in detail by SEM, TEM, XPS and Raman spectra. The as-prepared Ni(Fe) (oxy)hydroxide/NFs electrocatalysts show greatly enhanced OER activity and stability. The optimized NiFe (oxy)hydroxide/NFs bimetallic electrocatalysts achieve a current density of 10 mA cm−2 at the overpotential of only 268 mV with a small Tafel slope of 53.6 mV dec-1. During 28 h long term stability test at 10 mA cm−2, there is negligible increase in the required overpotential. These findings demonstrate that non-thermal laser-induced water plasma is a promising and efficient way to prepare highly efficient electrocatalysts with dynamic surface structures and high valence metal sites.

Interface-Rich Highly Oxophilic Copper/Tin–Oxide Nanocomposite on Reduced Graphene Oxide for Efficient Electroreduction of CO2 to Formate

In recent days, it has been reported that bimetallic electrocatalysts can increase the activity for electrochemical formate (HCOO–) production during CO2 reduction. However, they still have some apparent drawbacks such as poor selectivity and durability. In the current work, notable improvements in the electrochemical CO2 reduction (CO2RR) to formate production were accomplished by incorporation of reduced graphene oxide (rGO) into nanostructured bimetallic CuSnOx electrocatalysts (CuxSnOx/rGO). The interface-rich mixed crystalline–amorphous nanostructured Cu0.33SnOx/rGO nanocomposite is able to enhance the electrocatalytical activity, resulting in conversion of CO2 to formate with lower overpotential of 590 mV vs RHE. The control experiments show that the presence of SnOx in the catalyst considerably increased electrocatalytic activity and product selectivity toward formate production. Further, the increased oxophilicity of the Cu0.33SnOx/rGO nanocomposite supports the plausible CO2 reduction mechanism through the formation of bicarbonate intermediate, as demonstrated by CO stripping studies. The Cu0.33SnOx/rGO had maximum formate faradaic efficiency (80.62%) at lower potential of −0.69 V (RHE), which is 2.09 and 1.85 times better than those of CuSnOx/rGO and Cu3SnOx/rGO nanocomposites, respectively. The catalytic performance may be attributed to synergistic interaction, the presence of interfaces, higher electrochemical surface area, and the mixed crystalline–amorphous nature of Cu0.33SnOx/rGO nanocomposite. Thus, the obtained results gave rise to a practical method for boosting the activity and product selectivity of electrocatalysts for efficient CO2 conversion.

High-performance bimetallic In-Pb for electrocatalytic hydrogenation of levulinic acid

The challenge in the electrochemical reduction of levulinic acid (LA) lies in designing highly selective, energy-efficient, and non-precious-metal electrocatalysts that minimize the competitive hydrogen evolution reaction during LA conversion. Herein, we reported a facile pulsed electrodeposition strategy to fabricate bimetallic electrocatalysts with different combinations of lead (Pb), indium (In), tin, and cadmium supported by free-standing carbon felts (CFs). The as-prepared bimetallic self-supporting electrodes were examined for the electrochemical hydrogenation (ECH) of LA. The resulting InPb/CF electrocatalysts showed superior performance among the bimetallic catalysts. In addition, it was demonstrated that the catalytic performance of bimetallic samples was better than that of the corresponding monometallic samples. Notably, the In72.4Pb27.6/CF exhibited the best performance for ECH of LA, leading to 86.1 % of LA conversion, 99.7 % of selectivity towards valeric acid and 60.8 % of Faradaic efficiency at −1.5 V vs RHE. The excellent performance is mainly attributed to the modification of the electronic structures by the ligand and strain effects. Meanwhile, the relatively high electrochemically active surface area and the low charge transfer resistance are also conducive to improving the catalytic performance.

Evaluation of Pd-Co Bimetallic Electrocatalysts in the Formic Acid Oxidation Reaction

The main focus of this research is the synthesis and evaluation of Pd-Co bimetallic catalysts, in the formic acid electrochemical oxidation reaction (FAOR). The catalysts used were synthesized by electrodeposition using a choline chloride and urea Deep Eutectic Solvent (DES) termed reline, as electrolytic medium. Electrodeposition potentials were previously selected after analysis by Cyclic Voltammetry (CV) and used in Chronoamperometry (CA). The electrode modified with bimetallic nanoparticles (NPs) was used for FAOR, which is a key reaction in direct formic acid fuel cells (DFAFCs). Electrodeposits were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) to determine diameters, morphology and analysis of elements that make up the bimetallic NPs.

Copper-based bimetallic electrocatalysts for CO2 reduction: From mechanism understandings to product regulations

Copper-based bimetallic electrocatalysts for CO2 reduction: From mechanism understandings to product regulations

Efficient Pt-based nanostructured electrocatalysts for fuel cells: One-pot preparation, gradient structure, effect of alloying, electrochemical performance

This paper proposes an environmentally friendly one-pot synthesis approach for the PtCu and PtNi nanoparticles with the gradient structure on the carbon support. This method offers exceptional advantages over other approaches. Among them there is a surfactant-free synthesis, being low-temperature, simple, fast, and one-pot. The bimetallic electrocatalysts with a reduced platinum content for proton-exchange membrane fuel cells have been obtained. The proposed method is promising in terms of scaling and transition to commercial production. In this study, we first attempted to apply the gradient synthesis strategy to the PtNi/C catalysts in order to make this method versatile. We obtained the high-performance PtNi/C and PtCu/C catalysts, exhibiting the specific ORR activity higher than that of the commercial Pt/C catalyst by 3 and 4.6 times, respectively.

Studies on the effect of solvent for the synthesis of low‐cost and efficient Pt‐Co/CAB cathode electrocatalyst to enhance the performance of a hydrogen‐based PEMFC

AbstractHighly efficient and low‐cost Pt‐Co/CAB bimetallic cathode electrocatalysts were synthesized for hydrogen‐based proton exchange membrane fuel cell (PEMFC) using three different types of solvent, namely, dimethyl sulphoxide (DMSO), dimethylformamide (DMF), and ethylene glycol (EG). The physical characterization of synthesized cathode electrocatalysts Pt‐Co/CAB‐DMSO, Pt‐Co/CAB‐DMF and Pt‐Co/CAB‐EG was performed by scanning electron microscope–energy‐dispersive X‐ray (SEM–EDX), X‐ray diffraction (XRD), and transmission electron microscopy (TEM) techniques, whereas the electrochemical investigation of all three Pt‐Co/CAB electrocatalysts was performed by CV and EIS studies. The synthesized Pt‐Co/C‐EG electrocatalyst produced the highest power density of 19.61 mW/cm2 at a room temperature of 33°C. The power density increased to 26.11 mW/cm2, that is, 133%, when the cell operating temperature was raised from 33 to 70°C. The excellent performance of the Pt‐Co/CAB‐EG cathode electrode proves that it can be recommended as a commercial electrocatalyst for PEMFC cathode. In addition, the EG/EG was identified as the best solvent for the synthesis of Pt‐Co/CAB cathode electrocatalysts.

Cation Dissolution-Induced Structural Transformation and Enhanced Stability for Ni–Ir Bimetallic Electrocatalysts during the Oxygen Evolution Reaction in Acid

To develop stable electrocatalysts for the oxygen evolution reaction (OER) in acid, it is essential to understand the degradation mechanisms on the catalyst surface. In this work, we compare the OER performance of two Ni–Ir bimetallic oxides (Li2Ir1–xNixO3−δ with x = 0.25 and 0.75) in sulfuric acid. A dynamic structure transformation is observed on LINO-0.25 due to fast delithiation from the layered structure. The resulting catalyst demonstrates ∼10 times enhanced electrochemical activity but 70% less Ir dissolution compared to that of LINO-0.75 oxide. We propose that creating dynamic Li+/H+ exchange channels in structure may be beneficial for achieving a stable OER performance in acid.

Asymmetrical electrohydrogenation of CO2 to ethanol with copper–gold heterojunctions

Copper is distinctive in electrocatalyzing reduction of CO2 into various energy-dense forms, but it often suffers from limited product selectivity including ethanol in competition with ethylene. Here, we describe systematically designed, bimetallic electrocatalysts based on copper/gold heterojunctions with a faradaic efficiency toward ethanol of 60% at currents in excess of 500 mA cm-2. In the modified catalyst, the ratio of ethanol to ethylene is enhanced by a factor of 200 compared to copper catalysts. Analysis by ATR-IR measurements under operating conditions, and by computational simulations, suggests that reduction of CO2 at the copper/gold heterojunction is dominated by generation of the intermediate OCCOH*. The latter is a key contributor in the overall, asymmetrical electrohydrogenation of CO2 giving ethanol rather than ethylene.

Electrochemical Activation and Its Prolonged Effect on the Durability of Bimetallic Pt-Based Electrocatalysts for PEMFCs

The present study, concerned with high-performance ORR catalysts, may be a valuable resource for a wide range of researchers within the fields of nanomaterials, electrocatalysis, and hydrogen energy. The objects of the research are electrocatalysts based on platinum–copper nanoparticles with onion-like and solid-solution structures. To evaluate the functional characteristics of the catalysts, the XRD, XRF, TEM, HAADF-STEM, and EDX methods, as well as the voltammetry method on a rotating disk electrode have been used. This work draws the attention of researchers to the significance of applying a protocol of electrochemically activating bimetallic catalysts in terms of the study of their functional characteristics on the rotating disk electrode. The choice of the potential range during the pre-cycling stage has been shown to play a crucial role in maintaining the durability of the catalysts. The activation of the PtCu/C catalyst during cycling of up to 1.0 V allows for an increase in the durability of the catalysts with onion-like and solid-solution structures of nanoparticles by 28% and 23%, respectively, as compared with activation of up to 1.2 V.

Construction of CoFe bimetallic phosphide microflowers electrocatalyst for highly efficient overall water splitting

In this study, CoFe bimetallic phosphide microflowers electrocatalyst are supported on nickel foam. The bimetallic composition and phosphating can effectively improve the OER and HER performances and realize optimized overall water splitting performance. It requires only an overpotential of 68 mV in 1 M KOH to reach a current density of 10 mA·cm−2 for HER and only 227 mV for OER. When optimal sample (CoFe10%-P/NF) was used for overall water splitting, a low cell voltage of 1.610 V is required at 10 mA·cm−2 in alkaline solution. The stability was also good. This study provides feasible proposals for overall water splitting.

Iron-doped bimetallic boride Fe-Ni2B/NF-x nanoparticles toward efficient oxygen evolution reaction at a large current density.

Transition metal borides are seen as potential candidates for oxygen evolution reaction (OER) electrocatalysts due to their superconductivity and rich surface-active sites, but monometallic borides only display generic OER catalytic performance. Hence, iron-doped bimetallic boride nanoparticles (Fe-Ni2B/NF-x) on Ni foam are reported and applied as superior OER electrocatalysts with high catalytic activities. Such bimetallic boride electrocatalysts require overpotentials of only 194 and 336 mV to afford current densities of 10 and 500 mA cm-2 toward the OER in 1 M KOH electrolyte, and Fe-Ni2B/NF-3 can retain this catalytic stability for at least 100 h at 1.456 V. The performance of the improved catalyst Fe-Ni2B/NF-3 matches the best nickel-based OER electrocatalysts reported so far. Analysis of X-ray photoelectron spectroscopy (XPS) and Gibbs free energy calculations show that Fe-doping essentially acts to modulate the electronic density of Ni2B and lower the free energy of O adsorption in the OER. The charge density differences and d-band theory proved that Fe sites have a high charge state and can be taken as catalytic sites for the OER. This proposed synthesis strategy provides a different view for preparing efficient bimetallic boride electrocatalysts.

Nitridation-free preparation of bimetallic oxide-nitride bifunctional electrocatalysts for overall water splitting.

A novel one-pot surfactant-free synthesis is presented for designing bimetallic oxide-nitride electrocatalysts with tunable morphologies using metal salts and nitrogen-rich precursors. This innovative approach eliminates the need for a distinct nitridation process. Bifunctional electrode Co3O4/MoO3/MoxNy achieved a current density of 10 mA cm-2 while maintaining a cell voltage of 1.52 V, outperforming many bimetallic oxide-nitride catalysts in the scientific literature.