Bifunctional Electrocatalysts Research Articles

Taking Advantage of Potential Coincidence Region: Insights into Gas Production Behavior in Advanced Self-Activated Hydrazine-Assisted Alkaline Seawater Electrolysis.

Water electrolysis assisted by hydrazine has emerged as a prospective energy conversion method for achieving efficient hydrogen generation. Due to the potential coincidence region (PCR) between the hydrogen evolution reaction (HER) and the electro-oxidation of hydrazine, the hydrazine oxidation reaction (HzOR) offers distinct advantages in terms of strategy amalgamation, device architecture, and the broadening of application horizons. Herein, we report a bifunctional electrocatalyst of interfacial heterogeneous Fe2P/Co2P microspheres supported on Ni foam (FeCoP/NF). Benefiting from the strong interfacial coupling effect between Fe2P and Co2P and the three-dimensional microsphere structure, FeCoP/NF exhibits outstanding bifunctional electrocatalytic performance, achieving 10 mA cm-2 with low overpotentials of 10 and 203 mV for HER and HzOR, respectively. Utilizing FeCoP/NF for both electrodes in HzOR-assisted water electrolysis results in significantly reduced potentials of 820 mV for 1 A cm-2 in contrast to the electro-oxidation of alternative chemical substrates. The presence of a potential coincidence region makes the application of self-activated seawater electrolysis realistic. The gas production behavior at different current densities in this interesting hydrogen production system is discussed, and some rules that are distinguished from conventional water electrolysis are summarized. Furthermore, a new self-powered hydrogen production system with a direct hydrazine fuel cell, rechargeable Zn-hydrazine battery, and hydrazine-assisted seawater electrolysis is proposed, emphasizing the distinct benefits of HzOR and its potential role in electrochemical energy conversion technologies powered by renewable sources.

Multiple strategies regulating the d-band center of Ni2P/NiFe2O4 @N-GTs hierarchical nanoarchitecture as efficient electrocatalyst for overall water splitting

The rational design of highly active electrocatalysts for water electrolysis remains challenging for green hydrogen utilization. Herein, guided by the correlation between the electroactivity and the d-band center (Ed), a novel hierarchical nanoarchitecture (Ni2P/NiFe2O4-VO@N-GTs) was fabricated, in which, Ni2P nanoparticles are grown on the oxygen vacancy-rich NiFe2O4 nanosheet arrays anchoring on N-doping graphene tubes. The results reveal that the multiple strategies including the vacancies and heterogeneous interface construction effectively induce the charge redistribution, and further adjust the Ed to the appropriate energy level, which endows the optimal balance between the adsorption and desorption ability of the catalyst to reaction intermediates, thus leading to the conspicuous electrocatalytic activity. Additionally, the hierarchical nanoarchitecture contributes to the exposure of more active sites, the efficiency of electron transfer, and the release of generated gas. Hence, Ni2P/NiFe2O4-VO@N-GTs presents superior bifunctional activity, especially a low overpotential of 194 mV at 10 mA cm−2 for OER. The corresponding overall water electrolyzer owns a lower cell voltage and long-term durability with continuously operating over 330 h at 100 mA cm−2, outperforming the most reported bifunctional electrocatalysts. This work presents an effective pathway for regulating the Ed through multiple strategies to improve the catalytic performance of catalysts.

CuNi alloy anchored on dual-substrate TiOx/N-doped carbon nanofibers as a bifunctional electrocatalyst for rechargeable zinc-air batteries

Development of non-noble metal-based electrocatalysts to enhance the performance of zinc-air batteries (ZABs) is of great significance, but it remains a formidable challenge due to their poor stability and activity. Herein, a bifunctional CuNi-TiOx/NCNFS electrocatalyst, featuring with electron-rich copper-nickel (CuNi) alloy nanoparticles anchored on titanium oxide/N-doped carbon nanofibers (TiOx/NCNFS), is constructed by a dual-substrate loading strategy. The introduction of TiOx has led to a significant increase in the stability of the dual-substrate. The strong electronic interaction between CuNi and TiOx strengthens the anchoring of active metal sites, thus accelerating the electron transfer. Theoretical calculations unclose that NCNFS can regulate the charge distribution of TiOx, inducing the charge transfer from NCNFS → TiOx → CuNi, thereby reducing the d-band center of Cu and Ni, which is beneficial to the desorption of intermediate oxide species of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Therefore, CuNi-TiOx/NCNFS delivers a remarkable bifunctional performance with a low OER overpotential of 258 mV at 10 mA cm−2 and an ORR half-wave potential of 0.85 V. When assembled into ZABs, CuNi-TiOx/NCNFS shows a low potential gap of 0.64 V, a higher power density of 149.6 mW cm−2 at 330 mA cm−2, and an outstanding stability for 250 h at 5mA cm−2. This study provides a novel approach by constructing dual-substrate to tune the electronic structure of active metal sites for efficient rechargeable ZABs.

Controlled Synthesis of MoNi4 Ultrathin Nanosheet Arrays as an Efficient Bifunctional Electrocatalyst for Urea-Assisted Hydrogen Production

Controlled Synthesis of MoNi₄ Ultrathin Nanosheet Arrays as an Efficient Bifunctional Electrocatalyst for Urea-Assisted Hydrogen Production

ZIF-67-derived Co-N-C supported nickel cobalt sulfide as a bifunctional electrocatalyst for sustainable hydrogen production via alkaline electrolysis.

As non-renewable resources are finite and cannot be utilized indefinitely, hydrogen (H2) has emerged as a promising alternative for clean and sustainable energy. The cost-effective hydrogen production to meet large-scale commercial demand poses a significant challenge. Water electrolysis, powered by electricity derived from renewable resources, stands out as a viable route towards sustainable hydrogen production, with electrocatalysis playing a pivotal role in this process. Notably, materials derived from metal-organic frameworks (MOFs) exhibit excellent physicochemical properties, making them promising candidates for electrocatalysis. In this study, we synthesized zeolitic imidazolate framework-67 (ZIF-67) and its derived Co-N-doped carbon (Co-N-C) supported NiCo2S4 on nickel foam (NF), namely NF@ZIF-67@NiCo2S4 and NF@Co-N-C@NiCo2S4, using a hydrothermal method. The electrocatalytic activity of these synthesized materials for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) was systematically evaluated using various electrochemical techniques. The NF@ZIF-67@NiCo2S4 material demonstrates overpotentials of 248 and 359 mV for OER and HER at the current density of 50 mA cm-2, whereas, NF@Co-N-C@NiCo2S4 exhibits overpotentials of 239 and 351 mV, respectively. Furthermore, the catalysts exhibit excellent stability in both OER and HER even under high applied potentials. Moreover, to assess their catalytic performance in a full-cell configuration, two alkaline electrolyzer cells were assembled: NF@ZIF-67@NiCo2S4(+)∥NF@ZIF-67@NiCo2S4(-) and NF@Co-N-C@NiCo2S4(+)∥NF@Co-N-C@NiCo2S4(-). These two electrolyzers demonstrated cell potentials of 1.62 V and 1.59 V at 10 mA cm-2, respectively, showcasing their efficacy in overall water-splitting.

A Multi‐Active Site Subnano Heterostructures Catalyst Grown In situ POM and Fe0.2Ni0.8Co2O4 onto Nickel Foam Toward Efficient Electrocatalytic Overall Water Splitting

AbstractDesigning efficient, durable, and cheap bifunctional electrocatalysts is a challenging goal in water splitting. Herein, trivanadium‐substituted Keggin‐type polyoxometalate H6PV3Mo9O40 (POM) and Fe0.2Ni0.8Co2O4 (FNCO) are in situ grown onto nickel foam (NF) yielding a self‐supporting nanoflower‐like heterojunction via convenient hydrothermal reaction. The POM‐Fe0.2Ni0.8Co2O4/NF as HER and OER electrocatalyst, displays low overpotential (89 and 259 mV) and high electrode stability at 10 mA cm−2. POM‐FNCO/NF as the cathode and anode requires a lower voltage (1.58 V) to provide 10 mA cm−2 for overall water splitting (OWS), which is better than that of commercial catalysts. The electronic sponge characteristics of POM provide more active sites and fast reaction kinetics for HER and OER. The synergy of POM and FNCO optimizes the electron distribution at the interface and enhances the intrinsic activity of HER/OER. Density Functional Theory (DFT) calculations show that water molecules preferentially bind to Co sites on POM‐FNCO. Additionally, POM has proton‐coupled electron transfer properties and its modified FNCO exhibits thermodynamic advantages. The synergistic effect of these two factors enables the efficient overall water splitting of POM‐FNCO. This study offers a novel pathway for the construction of self‐supporting efficient catalysts by in situ growth of POM nanoclusters and spinel oxide sub‐nanometer heterojunctions on NF.

The defect chemistry and machine learning study 5d transition metal doped on graphitic carbon nitride for bifunctional oxygen electrocatalyst with low overpotential

Searching for highly efficient bifunctional oxygen evolution reaction/oxygen reduction reaction (OER/ORR) electrocatalysts for sustainable and renewable clean energy is vital. However, these electrocatalyst designs remain cost-prohibitive for both experimental and computational studies. This paper systematically investigates 5d transition metal (5d TM) doped into graphitic carbon nitride (g-C3N3) as potential bifunctional OER/ORR electrocatalysts by considering the defect charge states through the defect chemistry study. Our formation energies results show that 33 kinds of 5d TM doped g-C3N3 have better stabilities in the different charge states. Among them, IrN×@C54N53 (Ir occupation N), IrN•@C54N53, PtN×@C54N53 (Pt occupation N), and Iri•@C54N54 (Ir interstitial sites) exhibit lower overpotentials. They are great candidates for bifunctional OER/ORR electrocatalysts. This is because adjusting the charge states of 5d-TM@g-C3N3 can tune the interaction strength of the oxygenated intermediates. Furthermore, machine learning shows that the charge transfer of TM atoms (Qe) and total magnetic moment (μB0) are the two most essential descriptors for OER and ORR overpotential, respectively. The charged defect adjusting of the bifunctional OER/ORR activity would develop the potential electrocatalysts for energy conversion applications.

Surfactant-free CuPd nano-alloy for N2H4 oxidation-assisted H2 evolution and H2O2 detection

The utilization of hydrazine oxidation reaction (HzOR) with a lower thermodynamic oxidation potential has been regarded as an efficient strategy for H2 generation through electrolysis. However, a highly efficient and stable bifunctional electrocatalyst for overall hydrazine (N2H4) splitting was scarce. This work verified promising CuPd nano-alloy as a bifunctional electrocatalys for energy-efficient electrolytic hydrogen production, with hydrazine assistance. It is demonstrated that the CuPd nano-alloy exhibited enhanced electrocatalytic activity for both cathodic and anodic reactions compared to pure Cu and Pd nanocrystals, benefiting from its favorable electronic structure. Under 1.0 M KOH electrolyte with 0.1 M N2H4, the surfactant-free CuPd nano-alloy only required a potential of 0.648 V to achieve the N2H4 splitting (OHzS). The surfactant-free surface maximized exposed active sites, which facilitated the adsorption and desorption of reactants, resulting in enhanced electrocatalytic activity. And working potential for HzOR by surfactant-free CuPd was only 50.4 % compared to the CuPd nano-alloy with surfactant. This work provided an efficient electrocatalyst for OHzS. The enhanced electro-catalytic performances resulting from the electronic structure of alloy and the surfactant-free interface effect have been thoroughly discussed and verified, which would be invaluable for the design of efficient electrocatalysts for H2 production.

π‐d Conjugated Copper Chloranilate with Distorted Cu‐O4 Site for Efficient Electrocatalytic Ammonia Production

AbstractUnderstanding the relationship between electrocatalytic performance and local structure at the molecular level is of great significance. Herein, a bifunctional electrocatalyst CuCA (CA = chloranilate) is constructed for both nitrogen reduction reaction (NRR) and nitrate reduction reaction (NO3RR). Combined structural analyses using Rietveld refinement, extended X‐ray adsorption fine structure (EXAFS), and pair distribution function (PDF) revealed a significant distortion of the Cu‐O4 structure. Benefitting from the unique local structure, Cu‐CA shows an impressive NH3 yield rate of 286.00 ug h−1 mg−1 (FE = 18.25%, ‐0.85 V vs RHE), 3180.00 ug h−1 mg−1 (FE = 90.3%, ‐0.9 V vs RHE) for NRR and NO3RR, respectively. In contrast, the pyrazine (Pyz) decorated compound Cu‐CA‐Pyz with a less distorted Cu‐O4 structure and fewer active sites show much lower activity. Density functional theory (DFT) calculations shed light on that the distorted nature can effectively regulate the electron density distribution, which can lower the energy barrier of adsorption and activation of the intermediate species, leading to the enhanced activity. These findings may give new insight into the structural‐property relationship and open up opportunities for the exploration of efficient electrocatalysts.

Enhanced activity of electrodeposited WO3 thin films as bi-functional electrocatalysts for water splitting

The ultimate goal of the hydrogen economy is to develop an efficient and cost-effective electrocatalyst that can accelerate hydrogen synthesis from water without or with little additional energy. This study describes a unique surface modified electrodeposited nano-sized tungsten oxide (WO3) as an intriguing bi-functional electrocatalyst for OER in alkaline and HER in acidic conditions. The nano-WO3 was synthesized hydrothermally and electrodeposited on a fluorinated tin oxide (FTO) electrode. The highly uniform distribution of the WO3@FTO catalyst results in negligible charge transfer resistance, a large electroactive surface area, and increased water-splitting potential. During oxygen evolution reaction (OER), electrodeposited WO3@FTO initiates water splitting at an overpotential (η) of just 240 mV and represents a turnover frequency (TOF) of 0.59 sec−1. These results are comparable to previously reported electrocatalysts. Under an alkaline electrolyte, a current density of 15 mA/cm2 remained constant for several hours, indicating the high stability and durability of the electrodeposited WO3@FTO electrode. The electrode also performed well in hydrogen evolution reactions (HER). A Tafel slope of 46 mV/dec and −28 mV/dec was found for OER and HER, respectively, indicating an enhanced kinetics rate of reaction taking place at the electrode surface. Furthermore, in acidic conditions, the electrode represents a lower HER overpotential of 104 mV. The work provides a significant understanding of electrodeposited WO3@FTO electrodes and their role in electrochemical water splitting.

Synergistic effect of iron phthalocyanine and ultrafine cobalt nanoparticles for efficient CO2 electroreduction to syngas

Developing efficient electrocatalysts for CO2 electroreduction to syngas with a specific H2/CO ratio over a wide potential window is desperately required but still challenging. In this work, a series of dual-site catalysts composed of iron phthalocyanine (FePc) and ∼18 nm Cobalt nanoparticles (Co NPs) anchored on N-doped carbon matrix has been constructed from zeolitic imidazolate framework-67 (ZIF-67). Benefiting from the synergistic effect of FePc and Co NPs, the derived FePc/Co@N–C catalyst shows impressive capability for CO2 electrolysis to syngas. By varying the pyrolysis temperatures (600–800 °C) of ZIF-67 and the mass ratio of Co@N–C to FePc (1–3), an adjustable H2/CO ratio of 2–4 is obtained, and the value can be maintained stable within a potential window of −0.66 to −0.86 V vs. RHE in an H-type cell. Moreover, this electrocatalyst exhibits favorable stability without distinct performance decay. When conducted in a flow cell, an enhanced catalytic activity is demonstrated with an industrial current density (>100 mA cm−2) at −0.8 V vs. RHE and a steady H2/CO ratio of 2 from −0.4 to −0.6 V vs. RHE. This work provides a promising strategy of designing bifunctional electrocatalysts for syngas generation with stable H2/CO ratio across a wide potential range.

Bifunctional Chiral Electrocatalysts Enable Enantioselective α-Alkylation of Aldehydes.

Herein, we describe an innovative approach to theasymmetric electrochemical α-alkylation of aldehydes facilitated by a newly designed bifunctional chiral electrocatalyst. The highly efficient bifunctional chiral electrocatalyst combines a chiral aminocatalyst with a redox mediator. It plays a dual role as a redox mediator for electrooxidation, whilesimultaneously providingremarkable asymmetric induction for the stereoselective α-alkylation of aldehydes. Additionally, this novel catalyst exhibits enhanced catalytic activity and excellent stereoselective control comparable to conventional catalytic systems. As a result, this strategyprovides a new avenue for versatile asymmetric electrochemistry. Theelectrooxidationof diverse phenols enablesthe C-H/C-H oxidative α-alkylation of aldehydes in a highly chemo- and stereoselective fashion. Detailed mechanistic studies by control experiments and cyclic voltammetryanalysis demonstrate possible reaction pathways and the origin of enantio-induction.

Bifunctional Chiral Electrocatalysts Enable Enantioselective α‐Alkylation of Aldehydes

Bifunctional Chiral Electrocatalysts Enable Enantioselective α‐Alkylation of Aldehydes

Cobalt Nanoparticles Encapsulated in the Biomass-Derived Carbon: An Efficient and Bifunctional Electrocatalyst for Overall Water Splitting

Cobalt Nanoparticles Encapsulated in the Biomass-Derived Carbon: An Efficient and Bifunctional Electrocatalyst for Overall Water Splitting

Advancements in Rechargeable Zn-Air Batteries with Transition-Metal Dichalcogenides as Bifunctional Electrocatalyst.

Zinc-air batteries are promising energy storage devices owing to their high energy density, low cost, and environmental friendliness. However, the development of durable and efficient bifunctional electrocatalysts is a major concern for Zn-air batteries. In this review, we summarize the recent progress on transition metal dichalcogenides (TMDs) as bifunctional electrocatalysts for Zn-air batteries. We discuss the advantages of TMDs, such as high activity, good stability, and tunable electronic structure, as well as the challenges, such as low conductivity, poor durability, and limited active sites. We also highlight the strategies for fine-tuning the properties of TMDs, such as defect engineering, doping, hybridization, and structural engineering, to enhance their catalytic performance and stability. We provide a comprehensive and in-depth analysis of the applications of TMDs in Zn-air batteries, demonstrating their potential as low-cost, abundant, and environmentally friendly alternatives to noble metal catalysts. We also suggest future directions like exploring new TMDs materials and compositions, developing novel synthesis and modification techniques, investigating the interfacial interactions and charge transfer processes, and integrating TMDs with other functional materials. This review aims to illuminate the path forward for the development of efficient and durable Zn-air batteries, aligning with the broader objectives of sustainable energy solutions.

Hybridization of bimetallic cobalt-molybdenum oxide multihole nanosheets with selenium adulteration as advanced bifunctional electrocatalysts for boosting overall water splitting

Electrocatalytic water splitting produces green and pollution-free hydrogen as a clean energy carrier, which can effectively alleviate energy crisis. In this paper, bimetallic and selenium doped cobalt molybdate (Se-CoMoO4) nanosheets with rough surface are resoundingly prepared. The multihole Se-CoMoO4 nanosheets display ultrathin and rectangular architecture with the dimensions of ∼ 3.5 μm and 700 nm for length and width, respectively. The Se-CoMoO4 electrocatalyst shows remarkable water electrolysis activity and stability. The overpotentials of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are 270 and 63.3 mV at 10 mA cm−2, along with low Tafel slopes of 51.6 and 62.0 mV dec-1. Furthermore, the Se-CoMoO4 couple electrolyzer merely requires a cell voltage of 1.48 V to achieve 10 mA cm−2 current density and presents no apparent attenuation for 30 h. This investigation declares that the hybridization of transition bimetallic oxide with nonmetallic adulteration can afford a tactic for the preparation of bifunctional non-precious metal-based electrocatalysts.

Tailoring the composition of a non-noble, Cubic Shaped MnSn(OH)6 Bi-functional electrocatalysts for methanol and urea oxidation reactions in alkaline solutions

A systematic study of the effect of Sn-precursor concentration on the composition of (MnSn(OH)6) is carried out, and the samples' structural, morphological, and electrochemical variations are investigated. Four different SnCl2·5H2O precursor concentrations (5, 10, 20, and 40 mM) are varied to synthesize MnSn(OH)6 electrocatalysts, denoted as MS-1, MS-2, MS-3, and MS-4, respectively, using a hydrothermal method. All four samples' crystal structure and chemical states are identified using X-ray diffraction analysis and X-ray photoelectron microscopy. Morphological studies are carried out using scanning electron and transmission electron microscopy studies. The electrocatalytic performance and the stability of the synthesized samples are evaluated using cyclic voltammetry and chronoamperometry. Among the samples, MS-3, which has an optimized ratio of Mn/Sn, displayed the highest current density values of 80.3 mA g−1 and 84.7 mA g−1 at a higher potential of 0.7 V for the urea oxidation reaction in the presence of 0.33 M urea + 1.0 M KOH and for the methanol oxidation reaction in the presence of 0.5 M methanol + 1.0 M KOH, respectively. This intrinsic activity of MS-3 samples is due to its more significant electrochemically active surface area value of 208 mF cm−2, primarily because of the dominance of Mn3+ on the surface. Furthermore, MS-3 displayed reduced overpotential, as evidenced by the onset potential of 1.45 (V vs RHE) @ 10 mA cm−2, indicating enhanced electrocatalytic performance. These findings highlight the importance of tuning the Mn/Sn metal ratio to design and develop cost-effective non-precious electrocatalysts for urea and methanol oxidation reactions.

High-Performance Bifunctional Electrocatalysts for Flexible and Rechargeable Zn-Air Batteries: Recent Advances.

Flexible rechargeable Zn-air batteries (FZABs) exhibit high energy density, ultra-thin, lightweight, green, and safe features, and are considered as one of the ideal power sources for flexible wearable electronics. However, the slow and high overpotential oxygen reaction at the air cathode has become one of the key factors restricting the development of FZABs. The improvement of activity and stability of bifunctional catalysts has become a top priority. At the same time, FZABs should maintain the battery performance under different bending and twisting conditions, and the design of the overall structure of FZABs is also important. Based on the understanding of the three typical configurations and working principles of FZABs, this work highlights two common strategies for applying bifunctional catalysts to FZABs: 1) powder-based flexible air cathode and 2) flexible self-supported air cathode. It summarizes the recent advances in bifunctional oxygen electrocatalysts and explores the various types of catalyst structures as well as the related mechanistic understanding. Based on the latest catalyst research advances, this paper introduces and discusses various structure modulation strategies and expects to guide the synthesis and preparation of efficient bifunctional catalysts. Finally, the current status and challenges of bifunctional catalyst research in FZABs are summarized.

Ultralow palladium doped C4N as a potential bifunctional electrocatalyst for zinc-air battery

It is an important task for designing a facile bifunctional electrocatalyst that is applied to a zinc-air battery (ZAB). Herein, the 2D C4N is synthesized by hydrothermal method, and ultralow noble metal palladium (Pd) is doped into the C4N to form Pd-C4N. The Pd-C4N has a low ΔE of 0.76 V in 0.1 M KOH, which is a good candidate as the bifunctional electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the ZABs. This work provides a design idea of modified carbon-based material for bifunctional electrocatalysts.

Fe nanoparticles assembled on N-doped porous carbon for superior overall water splitting

In traditional electrocatalysis research, the large size of transition metal particles often leads to self-aggregation, significantly impairing their conductivity and electrocatalytic performance. In this work, the advanced electrocatalysts have been developed by assembling high-content Fe nanoparticles on N-doped porous carbon (named as Fe/NPC-X) using a hydrothermal process combined with in situ reduction treatment. The synergistic interaction between Fe nanoparticles and N-doped carbon enhances electron transfer and increases the adsorption capacity for water molecules. The hierarchical porous structure of the material also enlarges the surface area available for reactants, optimizing both diffusion and catalytic efficiency. As a result, the developed bifunctional electrocatalysts, Fe/NPC-2 and Fe/NPC-3, demonstrate overpotentials of 80 mV and 255 mV for hydrogen and oxygen evolution reactions, respectively, at a current density of 10 mA/cm². Moreover, the overall water splitting device (Fe/NPC-2 (+)||Fe/NPC-3 (-)) exhibits outstanding water-splitting performance, achieving a voltage of 1.553 V at 10 mA/cm². Overall, this work presents a promising strategy to address the challenges associated with low content and large particle size of transition metals in bifunctional electrocatalysts, leading to highly efficient bifunctional electrocatalysts with enhanced catalytic activity and excellent cycling stability.