Bifunctional Electrocatalysts Research Articles

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.

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.

Interfacial engineering for the construction of iron sulfide/boride nanosheets heterostructure bifunctional electrocatalysts for high-efficiency overall water splitting

Iron-based materials have been extensively studied and applied as electrocatalysts. However, the electronic structure of iron itself is not conducive to effectively activating adsorbed intermediates, leading to slower kinetic steps. In this study, a heterogeneous composite catalyst with a nano-sheet array structure consisting of iron boron/sulfide (FeS@Fe2B/IP) was successfully prepared through a two-step process involving boriding and sulfidation of iron plates. The nanosheet array structure provides numerous catalytic active sites, promotes effective contact between electrolytes and catalytic sites, and enhances the apparent reaction rate of the catalyst. Additionally, the heterogeneous interface of FeS/Fe2B plays a crucial role in regulating the electronic structure of the metal Fe site, improving charge transfer rates, and accelerating electrocatalytic reaction kinetics. Ultimately, FeS@Fe2B/IP demonstrates outstanding water splitting performance, with only 177 and 191 mV overpotential providing 10 mA cm−2 toward HER and OER, respectively. Furthermore, it achieves a high current density of 500 mA cm−2 at 473 and 520 mV overpotentials for HER and OER, respectively. In addition to its excellent performance in water splitting applications, a bipolar alkaline cell was constructed using the FeS@Fe2B/IP bifunctional catalyst. This achieved current densities of 10 and 100 mA cm−2 at potentials of 1.63 and 1.75 V. Moreover, the catalytic stability of the FeS@Fe2B/IP system remained consistent for nearly 50 hours at current densities of 10 and 100 mA cm−2. These results confirm that FeS@Fe2B/IP is indeed a high-performance bifunctional electrocatalytic material which can significantly improve energy utilization efficiency in various applications.

Bifunctional 0D carbon quantum dot cathode electrocatalyst coupled with atomic hydrogen and hydroxyl radicals for efficient removal of oxytetracycline hydrochloride

Efficient removal of antibiotics is difficult to achieve by conventional single-oxidation or reduction processes. Herein, a bifunctional cathodic electrocatalyst coupling atomic hydrogen (H*) reduction with hydroxyl radical (·OH) oxidation in an efficient electrocatalytic process was developed for the effective degradation of oxytetracycline hydrochloride (OTC). Pd particles were dispersed on B-doped carbon quantum dots to prepare a Pd-B-doped carbon quantum dots/titanium (Pd-BCQD/Ti) electrode as a bifunctional cathode catalyst. The electrode can simultaneously generate H* through the H2O/H+ reduction process, H2O2 through the oxygen reduction process, and then generate ·OH. H* performs nucleophilic hydrogenation reduction of OTC molecules, and ·OH performs electrophilic oxidation of the carbon skeleton, and both act synergistically with the active chlorine species (HClO) generated at the anode. The experimental results showed that the electrode achieved 90.50 % removal of OTC within 60 min. In addition, the Pd-BCQD/Ti electrode reduces energy consumption while increasing current efficiency. The degradation effect was more than 85.80 % in the pH range of 3∼9, indicating fairly stable catalytic activity over a wide pH range. The degradation efficiency was basically unchanged after ten cycles, and the reactivity was still high in the actual water. Intermediates were analyzed based on LC-MS to explore the degradation pathways of OTC. The toxicity of the intermediates generated during OTC degradation was predicted based on quantitative conformational relationships. This study provides a feasible strategy for the preparation of bifunctional catalysts based on zero-dimensional BCQD for efficient green antibiotic wastewater treatment.

Nickel oxide/nickel nanohybrids for oxygen and hydrogen evolution in alkaline media

Ni-based materials are cost-efficient electrocatalysts for the oxygen and hydrogen evolution reactions (OER and HER). Specifically, high-valence nickel oxides have been recently identified as highly active for both reactions; however, the origin of their activity during operation, particularly towards the HER, is still undefined. Herein, electrodeposition was used to produce Ni-based electrocatalysts supported on carbon fiber paper, followed by UV/O3 treatment to oxidize and modify their surface chemistry. The resulting electrodes were composed of nanoclusters formed by a metallic nickel core and ultrathin sheets of a high-valence nickel oxide whose crystalline structure was similar to NiO2, with Ni2+/Ni3+ oxidation states. Upon investigating the effect of the electrochemical conditioning of these high-valence nickel oxide/nickel electrodes, confirming the formation of surface β-Ni(OH)2. This surface layer improved the performance of the electrode by providing active sites for H2O adsorption and dissociation, as indicated by detailed density functional theory (DFT) calculations. The origin of the higher HER activity of β-Ni(OH)2 (001) surface compared to NiO2 (2D), and Ni (111) surfaces is attributed to its unique electronic structure. The high valence nickel oxide/nickel electrodes possessed robust long-term OER and HER stability over 24h Finally, the potential for modifying the structural composition of these electrodes and their use as bifunctional electrocatalysts for the water-splitting reaction was demonstrated by using the resulting electrodes in an electrolyzer coupled with/without a photovoltaic cell.

Construction of bimetallic phosphide FexCo1−xP nanostructured array as a bifunctional electrocatalyst for overall water splitting

Construction of bimetallic phosphide FexCo1−xP nanostructured array as a bifunctional electrocatalyst for overall water splitting

MOF‐Derived FeCoO/N‐Doped C Bifunctional Electrode for H2 Production Through Water and Glucose Electrolysis

AbstractThe glucose oxidation reaction (GOR) is a potential alternative to water oxidation because of its relatively low thermodynamic potential and the high availability of glucose. Herein, a FeCoO/N‐doped C electrode derived from metal–organic framework (MOF) materials is applied, which is synthesized in several steps through the controlled deposition of Fe–Co oxide nanocatalysts onto Co –N‐doped C nanofibers on a Ni foam substrate and demonstrate exceptional electrocatalytic activity for both the GOR and overall water splitting. Here, a bifunctional electrocatalyst derived from MOF, FeCoO/N‐doped C is reported, for glucose oxidation reaction (GOR) and hydrogen evolution reaction (HER). The MOF‐derived FeCoO/N‐doped C (+/‐) as a bifunctional electrocatalyst exhibits a cell voltage of 1.4 V for the GOR&HER, to reach a current density of 10 mA cm−2, which is 280 mV lower than that for the oxygen evolution reaction (OER)&HER (1.68 V). This study reveals that GOR is an energy‐efficient and affordable source of H2 and value‐added chemicals.

Copper dual-doping strategy of porous carbon nanofibers and nickel fluoride nanorods as bi-functional oxygen electrocatalysis for effective zinc-air batteries

Designing and developing efficient, low-cost bi-functional oxygen electrocatalysts is essential for effective zinc-air batteries. In this study, we propose a copper dual-doping strategy, which involves doping both porous carbon nanofibers (PCNFs) and nickel fluoride nanoparticles with copper alone, successfully preparing copper-doped nickel fluoride (NiF2) nanorods and copper nanoparticles co-modified PCNFs (Cu@NiF2/Cu-PCNFs) as an efficient bi-functional oxygen electrocatalyst. When copper is doped into the PCNFs in the form of metallic nanoparticles, the doped elemental copper can improve the electronic conductivity of composite materials to accelerate electron conduction. Meanwhile, the copper doping for NiF2 can significantly promote the transformation of nickel fluoride nanoparticles into nanorod structures, thus increasing the electrochemical active surface area and enhancing mass diffusion. The Cu-doped NiF2 nanorods also possess an optimized electronic structure, including a more negative d-band center, smaller bandgap width and lower reaction energy barrier. Under the synergistic effect of these advantages, the obtained Cu@NiF2/Cu-PCNFs exhibit outstanding bi-functional catalytic performances, with a low overpotential of 0.68 V and a peak power density of 222 mW cm−2 in zinc-air batteries (ZABs) and stable cycling for 800 h. This work proposes a one-step way based on the dual-doping strategy, providing important guidance for designing and developing efficient catalysts with well-designed architectures for high-performance ZABs.

CO2- tolerant CuFe2O4 as Bifunctional Electrocatalyst for Transition from Rechargeable Li-O2 to Li-CO2 Batteries

CO2-tolerant rechargeable Lithium-Air batteries are seen as a high-performing alternative to Li-ion batteries. They utilize O2 from the air, reducing it at the cathode to form lithium peroxide (Li2O2) during discharge which is then oxidized to form lithium-metal and freeing O2 during charging. Most of the present studies involve pure O2 as the cathode material instead of aerial O2, which has a stiff-challenge due to atmospheric CO2 which produces Li2CO3 during discharge, posing a resistive load on the battery if not re-oxidized on charging. Ideally, presence of CO2 should enhance the charge-storage capacity if it is cycled reversibly. Thus, present research aims at taking advantage of both O2 and CO2 by employing metallic Cu on CuFe2O4 catalyst, synthesized from a one-step auto-combustion route. The Cu metal present in the catalyst leads to a low surface-area, yet the catalyst demonstrates excellent oxygen reduction reaction and moderate oxygen evolution reaction activity. excellent CO2 reduction reaction activity, oxidizing both the Li2O2 and the Li2CO3 during charge in both 10% CO2 and 100% CO2 atmospheres. The fabricated Li-CO2 battery operates for practical application, suggesting the suitability of the catalyst for the transition from practical Li-O2 battery to Li-Air battery.

Enhanced overall water splitting by morphology and electronic structure engineering on pristine ultrathin metal-organic frameworks

Metal-organic frameworks (MOFs) have caused extensive attention attributed to their widespread applications including electrocatalysis by virtue of their distinctive structural characteristics. However, the direct application of pristine MOFs as bifunctional electrocatalysts is quite challenging due to their insufficient active sites and poor electrical conductivity. In this research, the ultrathin tri-metal (Fe, Co, and V) doped FeCoV-NiMOF nanosheet arrays were prepared through a facile hydrothermal method. Benefiting from the distinctive ultrathin (1.5 nm) nanosheet arrays and electronic structure reconfiguration induced by heteroatom doping, the prepared FeCoV-NiMOF displays the low overpotentials of 238, 309, and 408 mV for oxygen evolution reaction (OER) and 144, 255, and 349 mV for hydrogen evolution reaction (HER) at the current densities of 10, 100, and 1000 mA cm−2, respectively, outperforming the vast majority of previously reported bifunctional pristine MOFs. The electrolytic cell utilizing FeCoV-NiMOF as both cathode and anode requires just 1.61 V to attain 10 mA cm−2 and displays superior stability of 100 h at 100 mA cm−2. In the anion exchange membrane electrolyzer, as-prepared FeCoV-NiMOF needs a low cell voltage of 2.16 V at 500 mA cm−2 for effective overall water splitting, demonstrating its substantial potential as bifunctional electrodes for H2 production. The viable and efficient strategy in this study exhibits great prospects to enrich the exploration of bifunctional MOF-based electrocatalysts with superior performance for renewable energy conversion.

Hydrogen production via alkaline seawater electrolysis using iron-doped nickel diselenide as an efficient bifunctional electrocatalyst

Green hydrogen production via seawater electrolysis is a promising pathway towards sustainable energy future. However, seawater splitting is hindered by the low stability and selectivity of electrocatalysts towards hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and faces severe electrode corrosion. Herein, we report the synthesis of highly active and durable Fe-doped nickel diselenide (Fe–NiSe2) nanoparticles supported on nickel foam as bifunctional electrocatalysts for efficient alkaline seawater electrolysis via an electrodeposition method followed by low-temperature annealing. The electrocatalytic properties of as-prepared Fe–NiSe2 toward HER and OER are investigated in different electrolytes. The optimized electrocatalyst (20-Fe-NiSe2) shows very low overpotential of 92 and 96 mV in alkaline (1.0 M KOH) and simulated seawater (1.0 M KOH + 0.5 M NaCl) electrolytes, respectively, to reach the current density of 10 mA cm−2 for HER. For the OER, 20-Fe-NiSe2 exhibits an overpotential of 333 and 311 mV in alkaline and simulated seawater electrolytes, respectively, to attain a current density of 100 mA cm−2. Further, full-cell studies are carried out with 20-Fe-NiSe2 as bifunctional electrocatalysts, which requires cell potential of 1.83 V and 1.81 V to deliver a current density of 100 mA cm−2 in alkaline and simulated seawater electrolytes, respectively. Additionally, the electrode shows tremendous potential for use in alkaline seawater electrolysis with stability over 100 h, at a current density of 100 mA cm−2, which is achieved at a low cell voltage of 1.87 V. The present work offers a simple, efficient, and cost-effective method for the development of heterogeneous Fe-doped nickel diselenide electrocatalysts for seawater electrocatalysis.

Oxidative ammonolysis modified lignin-derived nitrogen-doped carbon-supported Co/Fe composites as bifunctional electrocatalyst for Zn-air batteries

Oxidative ammonolysis modified lignin-derived nitrogen-doped carbon-supported Co/Fe composites as bifunctional electrocatalyst for Zn-air batteries

Boosting hydrogen production via alkaline water splitting: Impact of Ag doping in Gd2O3 nanosheet arrays

Hydrogen is a preferable renewable energy carrier in decarbonization efforts to develop sustainable and carbon-free economies due to its high energy density and absence of pollutant emissions during combustion. Among others, electrochemical water splitting (EWS) is a sustainable and eco-friendly technology for producing green hydrogen, representing an essential initial step towards achieving carbon neutrality. In this study, we synthesized a bifunctional electrocatalyst by vertically anchoring Ag-doped Gd2O3 nanosheet arrays onto a three-dimensional nickel foam (NF) substrate. The developed materials were thoroughly investigated using various analytical techniques. Furthermore, the electrocatalyst effectively performed oxygen evolution reactions (OER) and hydrogen evolution reactions (HER). The Ag4%-Gd2O3/NF exhibited boosted HER activity, achieving higher current densities ranging from 10 to 400 mA cm−2 at an overpotential between 14 and 122 mV. This study also highlights the considerable impact of metal sites in both Ag4%-Gd2O3/NF and Gd2O3/NF on the HER catalytic process. Similarly, the Ag4%-Gd2O3 electrocatalyst exhibited superior OER activity, with an overpotential of 209 mV at 10 mA cm−2. The optimized composition also shows Tafel slope of 25 and 20 mVdec−1. Furthermore, Ag4%-Gd2O3 demonstrated the ability to generate oxygen gas bubbles in approximately 20 h for OER, making it an attractive material for energy conversion and storage devices.

In-situ building of multiscale porous NiFeZn/NiZn-Ni heterojunction for superior overall water splitting

The development of efficient nonprecious bifunctional electrocatalysts for water electrolysis is crucial to enhance the sluggish kinetics of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). A self-supporting, multiscale porous NiFeZn/NiZn-Ni catalyst with a triple interface heterojunction on nickel foam (NF) (NiFeZn/NiZn-Ni/NF) was in-situ fabricated using an electroplating−annealing−etching strategy. The unique multi- interface engineering and three-dimensional porous scaffold significantly modify the mass transport and electron interaction, resulting in superior bifunctional electrocatalytic performance for water splitting. The NiFeZn/NiZn-Ni/NF catalyst demonstrates low overpotentials of 187 mV for HER and 320 mV for OER at a current density of 600 mA/cm², along with high durability over 150 h in alkaline solution. Furthermore, an electrolytic cell assembled with NiFeZn/NiZn-Ni/NF as both the cathode and anode achieves the current densities of 600 and 1000 mA/cm2 at cell voltages of 1.796 and 1.901 V, respectively, maintaining the high stability at 50 mA/cm2 for over 100 h. These findings highlight the potential of NiFeZn/NiZn-Ni/NF as a cost-effective and highly efficient bifunctional electrocatalyst for overall water splitting.

Fabrication of nickel nanoparticles anchored on a 2D double transition metal MXene for efficient hydrogen and oxygen evolution reactions

Creating cost-effective and high-performing bifunctional electrocatalysts is a viable alternative to expensive noble metal electrocatalysts for water-splitting applications. A double transition metal MXene (Mo2TiC2Tx) has recently shown exceptional electrocatalytic activity because of its high conductivity, hydrophilicity, mechanical stability, electron mobility, and rich surface chemistry. In this study, we have created efficient bifunctional electrocatalytic properties of nano Ni decorated Mo2TiC2Tx MXene (Ni–Mo2TiC2Tx). The efficient and homogeneous incorporation of Ni on the 2D Mo2TiC2Tx surface and between the layers demonstrates remarkable electrocatalytic efficiency for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Among the different combinations, the 15 mmol Ni–Mo2TiC2Tx showed lower overpotential for the HER (ƞ10 = 153.9 mV) and OER (ƞ10 = 200.5 mV). Moreover, the Ni–Mo2TiC2Tx based electrocatalysts exhibit satisfactory electrochemical stability up to 5000 cycles. During the HER and OER process, Ni and Mo cations form a new oxy-hydroxide layer on the surface in the OH− environment indicating a faster surface self-reconstruction process of the surface structure and Ni/Mo oxy-hydroxide layer interacts with O and H atoms of adsorbed water and thus leading to superior HER and OER activity. This study introduces a straightforward and effective approach to creating a new category of MXene heterostructures, which significantly boosts the performance and durability of catalysts for the HER and the OER showing promise for future applications.