Bifunctional Electrocatalysts Research Articles

Heterointerface engineering of yolk-shell-structured Mn2O3/RuO2 for boosting oxygen electrocatalysis in rechargeable liquid and flexible zinc-air batteries

Rational construction of high-efficient bifunctional oxygen electrocatalysts is of crucial significance for rechargeable Zn-air batteries (ZABs). Here, the yolk-shell-structured Mn2O3/RuO2 heterojunction is purposely constructed via the Kirkendall effect as a robust bifunctional oxygen electrocatalyst for simultaneously driving oxygen evolution and reduction reactions (OER and ORR). The strong interactions between Mn2O3 and RuO2 induces the surface reconstruction that brings the electronic transfer from Mn to Ru, and the changes of coordination environments of metal atoms. Meanwhile, the yolk-shell structure enables maximum contact of the active sites with the electrolyte and prevents the dissolution and peroxidation of active species. As a result, the yolk-shell-structured Mn2O3/RuO2 shows an outstanding bifunctional activity with a very low potential gap of ΔE = 0.60 V. Moreover, the ZABs assembled with Mn2O3/RuO2 render a large open circuit voltage of 1.53 V, a high specific capacity of 742.1 mA h g−1 and an exceptional cycling stability over 850 h that significantly outperforms those of Pt/C+RuO2-based ZABs. Moreover, the self-made flexible solid-state ZAB with Mn2O3/RuO2 cathode also shows good charge–discharge reversibility and flexibility at different bending angles. This work provides a feasible method for the design of efficient oxygen electrocatalysts to promote the practical application of ZABs.

Leaf-like Multiphase Metal Phosphides as Bifunctional Oxygen Electrocatalysts toward Rechargeable Zinc-Air Batteries

Leaf-like Multiphase Metal Phosphides as Bifunctional Oxygen Electrocatalysts toward Rechargeable Zinc-Air Batteries

Fe-doped phosphide nanosheet array derived from prussian blue analogues for high-efficient electrocatalytic water splitting

Doping heterogeneous atoms can modulate electronic structure, which matters for creating efficient bifunctional electrocatalysts in realizing conversion of hydrogen and electricity. This study demonstrates that Fe-doped Ni5P4 nanosheet arrays on nickel foam (Fe–Ni5P4/NF) using Prussian blue analogues as precursors are successfully synthesized by straightforward hydrothermal reactions and phosphating. Fe–Ni5P4/NF exhibits great efficiency in creating hydrogen from water under alkaline conditions. The Fe–Ni5P4/NF dual electrode just need a minimal cell voltage of 1.54 V at 10 mA cm−2 and maintain operational stability for a minimum of 50 h, demonstrating outstanding bifunctional properties. The introduction of Fe modifies the electronic configuration for Ni5P4, substantially boosting the activity of the electrocatalyst. This study offers a framework for designing splendid bifunctional electrocatalysts through synergistic doping strategies in electrochemical applications.

A "Two-Pronged" Strategy to Boost Hydrogen Evolution Kinetics on NiFe-Based (Oxy)hydroxides via Oxygen Deficient Ni-Mo-Fe Coordinate Structures for Ultra-Stable Ampere-Level Alkaline Overall Water Splitting.

NiFe (oxy)hydroxides have been regarded as one of the state-of-the-art catalysts for oxygen evolution reaction (OER). Unfortunately, the sluggish hydrogen evolution reaction (HER) kinetics limit its application as bifunctional electrocatalyst for alkaline overall water splitting (OWS). Herein, a "two-pronged" strategy is proposed to construct highly active oxygen deficient Ni-Mo-Fe coordinate structures in NiFe (oxy)hydroxide (NFM-OVR/NF), which simultaneously reduces the energy barrier of Volmer and Heyrovsky steps during alkaline HER process and significantly accelerate the reaction kinetics. Consequently, NFM-OVR/NF delivers overpotentials as low as 25 and 234mV to achieve 10 and 1000mA cm-2 in 1.0M KOH, respectively. Furthermore, benefiting from excellent HER and OER activity, NFM-OVR/NF exhibits a remarkable OWS activity with cell voltages of 1.44V and 1.77V at 10 and 1000mA cm-2 in 1.0M KOH, and displays ultralong-term stability for 600h at 500mA cm-2, while remaining durable for 300h in an alkaline water electrolyzer in 30% KOH at 80°C. The calculated price per gallon of gasoline equivalent for the produced H2 is $ 0.92, which is much lower than 2026 U.S. Department of Energy target ($ 2.00), demonstrating feasibility and practicability of NFM-OVR/NF for industrial applications.

Rapid electrodeposition synthesis of partially phosphorylated cobalt iron phosphate for application in seawater overall electrolysis

To obtain hydrogen energy from seawater, it is of utmost importance to design an efficient bifunctional electrocatalyst that can be produced on a large scale and in a rapid manner. In this work, iron cobalt phosphate (CoFe-EP/NF) for long-term efficient and stable seawater electrolysis were rapidly synthesized by a simple electrodeposition. The study showed that metal phosphides/phosphates provided additional active sites for the catalysts for hydrogen evolution reaction (HER, 160 mV at 100 mA/cm2) and oxygen evolution reaction (OER, 266 mV at 100 mA/cm2), in alkaline seawater electrolyte (1 M KOH + seawater), respectively. Notably, the presence of phosphate groups facilitates the transformation of cobalt-iron metal phosphates into the truly reactive substance CoOOH, which improves the OER kinetics. In addition, the phosphate layer formed after catalyst activation avoids the occurrence of chlorine evolution reaction (CER) by shielding the adsorption of Cl−, thus enhancing the corrosion resistance and enabling long-term stable operation in seawater. The two-electrode overall seawater electrolysis easily reaches 100 mA/cm2 at 1.68 V and exhibit a long-term durability of more than 100 h. This study offers a viable approach for the synthesis of electrocatalysts with high activity and corrosion resistance, which is vital for the practical realization of large-scale seawater electrolysis.

Highly selective interconversion of quinoxaline and 1,2,3,4-tetrahydroquinoxaline over a spinel CuCo2O4 electrocatalyst supported by Ni foam

An efficient electrocatalytic hydrogen storage system using CuCo2O4 supported by Ni foam (CuCo2O4/NF) as a bifunctional electrocatalyst and quinoxaline as a hydrogen storage carrier was developed. Electrochemical tests were conducted at room temperature and atmospheric pressure. The results showed that the conversion and selectivity of hydrogenation reached 93 % and 99 %, respectively, within 3 h at −0.18 V (vs. RHE). Meanwhile, the conversion and selectivity of dehydrogenation both reached 100 % within 20 min at 1.30 V (vs. RHE). Moreover, due to the excellent durability of CuCo2O4/NF, the hydrogenation conversion remained as high as 89 % after 8 cycles.

Co/CoOx–N–C bifunctional nanocatalyst derived from carbothermally optimized graphene networks with in-situ formed zeolitic imidazolate framework for high performance zinc-air batteries

Rechargeable zinc-air batteries are underpinned by high-performance and durable bifunctional oxygen electrocatalysts. Among the platinum-group metals (PGMs)-free catalysts, the redox-active cobalt-nitrogen-carbon (Co/CoOx–N–C) based materials are promising, however require further structural improvements. This work utilises extremely porous graphene networks (EGO) of hierarchical porosity to in-situ grow ZIF-67 nanocrystals extensively and homogeneously within the porous structure. A simple carbonization of nanoZIF-67@EGO not only generates finely dispersed redox capable Co/CoOx–N–C active sites with the help of residual oxygen functional groups of EGO, but also produces 2-3 dimensional hierarchical porous and conducting structure, readily facilitating high electrochemical surface area. This characteristic structure synergistically contributes to rapid charge and mass transfer rates along with high activity and stability for both ORR and OER. Here, it is worth mentioning that to produce equivalent catalyst material involving different graphitic or template supports requires prolonged and multi-step synthesis routes. The optimized catalyst delivers low potential difference of 0.86 V for bifucntional activity by offering superb ORR half-wave potential of 0.83 V vs RHE and limiting current density of 5.85 mA cm−2 in 0.1 M KOH electrolyte. Zinc-air battery exhibits peak power density of ∼175 mW cm−2 and specific capacity of ∼767 mAh g−1, along with durable cycling round trip efficiency of >63 % (correspond to low voltage gap of ∼0.74 V). These characteristics are better than numerous M–N–C based catalysts reported in the literature. This new strategy holds a great potential to boost the development of diverse MOFs and carbon-based electrocatalysts for a wide range of energy storage and conversion technologies.

Construction of atom-scale Co/Fe/Ni M-N-C active sites within nitrogen-doped carbon spheres for high-performance bifunctional oxygen catalysts in rechargeable zinc-air batteries

Developing carbon-based catalysts with metal‑nitrogen‑carbon (M-N-C) active sites as efficient and low-cost bifunctional catalysts to replace precious metal catalysts for rechargeable zinc-air batteries devices has garnered significant attention. Herein, nitrogen-doped submicron carbon-based spherical bifunctional electrocatalysts (CNPD-CoFeNi) with abundant atom-scale Co/Fe/Ni M-N-C active sites and defects were synthesized. The introduction of massive amounts of Zn species increases the spatial distance of Co/Fe/Ni metal sites to prevent aggregation during pyrolysis, and the evaporation of Zn at high temperatures creates defects synergizing with M-N-C. Consequently, CNPD-CoFeNi possesses a stable carbon-based spherical structure, high electrical conductivity, rich nitrogen content, abundant atom-scale Co/Fe/Ni M-N-C active sites, and defects, displaying outstanding durability, oxygen reduction reaction (ORR) activity with a half-wave potential of 0.87 V, and satisfactory OER performance, surpassing or comparable with the state-of-art Pt/C and RuO2, respectively. Notably, liquid Zn-air batteries with CNPD-CoFeNi catalyst exhibit an exceptional high peak power density of 146.5 mW cm−2 and stable charge-discharge cycling over 270 h, outperforming Pt/C-RuO2 based devices. Additionally, the all-solid-state Zn-air battery also displays satisfactory practicability and stability. The synthesis strategy and its remarkable results provide valuable guidance and inspiration for the future advancement of precious metal substitutes in ORR/OER and rechargeable zinc-air batteries.

Metal–organic framework derived RuNiMo/NC for enhanced hydrogen production and methanol reforming electrolysis

It is important to probe the effect of doping of ultratrace content of precious metal and synergistic effects of multimetals on effective electrocatalysts for water splitting. Thus, ultratrace content Ru doping NiMo-NC were acquired through simple hydrothermal technology and high-temperature pyrolysis. Benefiting from porous structure, ultratrace content Ru doping and synergistic effect of multiple metals, RuNiMo-NC-2 presents the small overpotentials of 130 and 199 mV for MOR to achieve 10 and 100mA cm−2 in 1 mol/L potassium hydroxide with 5 mol/L methanol. The assembled water electrolyzer with the RuNiMo-NC-2||RuNiMo-NC-2 couple only requires 1.49 V to realize 10mA cm−2 for the overall water splitting in 1 mol/L potassium hydroxide with 5 M methanol. This paper offers a feasible method for designing bifunctional electrocatalysts with superior electrocatalytic performance, which can be used in hydrogen production through water electrolysis.

Computational screening of transition metal atom doped ZnS and ZnSe nanostructures as promising bifunctional oxygen electrocatalysts.

The design of bifunctional oxygen electrocatalysts showing high catalytic performance for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is of great significance for developing new renewable energy storage and conversion technologies. Herein, based on the first principles calculations, we systematically explored the electrocatalytic activity of a series of transition metal atom (Fe, Co, Ni, Cu, Pd and Pt)-doped ZnS and ZnSe nanostructures for OER and ORR. The calculated results revealed that Ni- and Pt-doped ZnS and ZnSe nanostructures exhibit promising electrocatalytic performance for both OER and ORR in comparison to the pristine ZnS and ZnSe nanostructures. Especially, the OER/ORR overpotentials of Ni-doped ZnS and ZnSe nanostructures are estimated to be 0.28/0.30 and 0.31/0.31 V, respectively, disclosing their great potential as bifunctional oxygen electrocatalysts. Moreover, it is found that Ni-doped ZnS and ZnSe nanostructures for OER and ORR are on the top of the volcano plots, evincing promising catalytic performance. Our results provide theoretical insights into a feasible strategy to synthesize highly efficient ZnS- and ZnSe-based bifunctional oxygen electrocatalysts in the future.

MOF-Derived Ni/NiO-C Nanocomposites as Bifunctional Electrocatalysts Capable of Driving Both ORR and OER.

Bifunctional electrocatalysts, capable of efficiently driving both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), are crucial for advancing electrochemical processes. While noble-metal-based catalysts are widely recognized for their role in oxygen processes, current state-of-the-art designs are limited to either ORR or OER activity, presenting a notable research gap. In addressing this challenge, we have developed a novel Ni/NiO-C nanocomposite catalyst derived from a nickel-based metal-organic framework (Ni-SKU-5). For the ORR, the Ni/NiO-C catalyst exhibits an onset potential of 0.95 V vs RHE in a 1.0 M KOH solution, coupled with a Tafel slope of -99 mV dec-1 at 1600 rpm. Moreover, the catalyst displays excellent stability, maintaining a performance of over 90% after 10 h of continuous reaction. Furthermore, the catalyst proves effective in the OER, boasting an overpotential of 370 mV (at 10 mA cm-2) and a Tafel slope of 114 mV dec-1, highlighting its bifunctionality. The bifunctional overpotential of the Ni/NiO-C composite is measured at 820 mV, surpassing that of the 20% Pt/C electrocatalyst (860 mV), highlighting its potential for practical applications. Comparative experiments establish the origin of the robust bifunctional reactivity toward the conformal hybrid structure, porous framework, and the synergistic effect operating among the constituents of the nanocomposite.

Designing NiCoS/CNTs composites for highly efficient bifunctional electrocatalyst in water splitting

Designing NiCoS/CNTs composites for highly efficient bifunctional electrocatalyst in water splitting

Eco-Friendly synergistic energy generation: Co-Ni2S4 nanoparticles with S-g-C3N4 as a dual-action electrocatalyst for sustainable water splitting

The most appealing technique for producing hydrogen fuel is electrochemical water splitting, which uses natural water cycle capabilities from renewable sources. The transition metal sulfide family includes nickel sulfide (NiS), which is promising for electrochemical water splitting as an exceptionally efficient, stable, and active electrocatalyst. Nickel sulfide (NiS), a series of cobalt-doped nickel sulfide (CoNi2S4) by varying weight percentages of Co (2, 4, 6, 8, wt %) and a series of sulfur-doped graphitic carbon nitride (SGCN) composite with 6 % CoNi2S4 by varying weight percentage of SGCN (10, 30, 50, 70, 90, wt %) were all synthesized using one-pot hydrothermal method. Structural morphologies and composition of the synthesized nanoparticles (NPs) and nanocomposites (NCs) were investigated using SEM, EDX, FTIR, and XRD characterization techniques. The electrochemical performance was examined via voltammetric, electrochemical impedance, and chronoamperometric studies. Outcomes suggest that composite 70 % SGCN@6 % CNS is the best electrocatalyst with the smaller Tafel slope (107 mVdec-1), lowest overpotentials (440 mV@10 mAcm−2), and minor charge transfer resistance (15 Ω) as electrode materials for electrochemical water splitting. The present research provides a workable approach for creating efficient bifunctional electrocatalysts for total water splitting, it can be inferred from the data.

Carbon Nanofibers Encapsulated CoNiFe Bifunctional Electrocatalysts for Durable Zn-Air Batteries at Room and −40 °C Ultralow Temperatures

Carbon Nanofibers Encapsulated CoNiFe Bifunctional Electrocatalysts for Durable Zn-Air Batteries at Room and −40 °C Ultralow Temperatures

Earth-Abundant Divalent Cation High-Entropy Spinel Ferrites as Bifunctional Electrocatalysts for Oxygen Evolution and Reduction Reactions

Earth-Abundant Divalent Cation High-Entropy Spinel Ferrites as Bifunctional Electrocatalysts for Oxygen Evolution and Reduction Reactions

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.

Ru doping triggering reconstruction of cobalt phosphide for coupling glycerol electrooxidation with seawater electrolysis

Seawater electrolysis is a promising approach for sustainable energy without relying on precious freshwater. However, the large-scale seawater electrolysis is hindered by low catalytic efficiency and severe anode corrosion caused by the harmful chlorine. In contrast to the oxygen evolution reaction (OER) and chlorin ion oxidation reaction (ClOR), glycerol oxidation reaction (GOR) is more thermodynamically and kinetically favorable alternative. Herein, a Ru doping cobalt phosphide (Ru-CoP2) is proposed as a robust bifunctional electrocatalyst for seawater electrolysis and GOR, for the concurrent productions of hydrogen and value-added formate. The in situ and ex situ characterization analyses demonstrated that Ru doping featured in the dynamic reconstruction process from Ru-CoP2 to Ru-CoOOH, accounting for the superior GOR performance. Further coupling GOR with hydrogen evolution was realized by employing Ru-CoP2 as both anode and cathode, requiring only a low voltage of 1.43 V at 100 mA cm−2, which was 250 mV lower than that in alkaline seawater. This work guides the design of bifunctional electrocatalysts for energy-efficient seawater electrolysis coupled with biomass resource upcycling.

Ni and Co-based bifunctional electrocatalysts supported on TiO2@C for oxygen evolution and reduction reactions

In the search for affordable, ecofriendly, and sustainable catalysts for energy-related processes, series of Ni and Co-based bifunctional hybrid electrocatalysts supported on TiO2@C were prepared and studied in the oxygen evolution (OER) and oxygen reduction reactions (ORR). The hybrid TiO2@C supports were prepared using three biomass precursors: furfural, chitosan and saccharose. The nature and dispersion of the metallic phases on those supports was evaluated as a function of the biomass-derived precursors. The prepared materials showed electrocatalytic activity towards ORR and OER reaction, being more active for the latter. Despite a lower performance than Pt/C benchmark, these materials are clearly at much lower costs. The long-term stability and performance of the catalysts were also performed. The number of electrons involved in both processes was determined and a mechanism is proposed for the understanding of the mechanism of reactions using the present materials. It can be concluded that the Ni and mainly Co-based electrocatalysts show a remarkable potential for use as alternative catalysts in fuel cells-related reactions.

Covalently grafting a covalent organic framework onto carbon nanotubes as a bifunctional electrocatalyst for overall water splitting.

We propose a simple strategy to fabricate a composite material consisting of amino-functionalized carbon nanotubes (NCNTs) grafted with a covalently bonded Ni(II)-based covalent organic framework (COF) for electrocatalytic water splitting. The resulting electrocatalyst demonstrates remarkable catalytic efficiency in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under alkaline conditions.

Free-standing FeNiCuCoBMo high-entropy alloy bifunctional electrocatalysts for efficient pH-universal water electrolysis

Utilizing the synergistic effects of multi-components has been proven to be a feasible approach to enhance water splitting electrocatalytic activity, since developing efficient and stable bifunctional electrocatalysts within a wide pH range remains a significant challenge. Herein, we report a FeNiCuCoBMo high-entropy alloy (HEA) prepared by dealloying, showing outstanding bifunctional electrocatalytic performance for HER and OER in a pH-universal electrolyte. After dealloying for 7 h, the HER and OER overpotentials of the HEA strips in 1.0 M KOH decreased by 22 mV and 25 mV, respectively.Impressively, the free-standing strips with the optimal compositions achieve low HER (82 mV in acid and 101 mV in alkali at 10 mA·cm−2) and OER (311 mV in acid and 245 mV in alkali at 10 mA·cm−2) overpotentials. In a full hydrolysis experiment, a current of 10 mA·cm−2 can run for 100 h with only 1.58 V, which is attributed to the ample exposure of highly active sites resulting from the synergistic effect of each element. Theoretical calculations further support these findings, showing that the electronegativity differences of the metallic elements in FeNiCuCoBMo result in abnormal activity at specific locations (Fe and Mo).Additionally, charge rearrangement and enhanced electronic conduction at the interface reduce the activation energy barrier, thereby improving the performance of the electrocatalysts.