Efficient Bifunctional Electrocatalysts Research Articles

Orange peel derived activated carbon supported Ni–Co3O4 as an efficient electrocatalyst for oxygen evolution and reduction reaction in alkaline media

This study focuses on the development of a cost-effective electrocatalyst with excellent activity and stability for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR), which is crucial for water electrolysis and fuel cell technologies. Waste orange peel is utilized as a carbon precursor to synthesize biomass-derived activated carbon (OPAC) with a unique three-dimensional sheet-like microstructure. Subsequently, a simple hydrothermal method is employed to modify the OPAC by introducing Ni-doped Co3O4, leading to the formation of a Ni–Co3O4/OPAC hybrid. We propose the Ni–Co3O4/OPAC hybrid as a highly efficient bifunctional electrocatalyst for both OER and ORR. Co3O4/OPAC and Co3O4 catalysts are also prepared for comparison. Remarkably, the Ni–Co3O4/OPAC hybrid exhibits significantly enhanced OER activity compared to Co3O4/OPAC and Co3O4 catalysts. It demonstrates a lower overpotential of 360 mV and a lower Tafel slope of 55.47 mV/dec, indicative of more efficient electrochemical performance. Moreover, in the ORR analysis, the Ni–Co3O4/OPAC hybrid displays a two-step pathway and achieves a higher ORR limiting current density compared to the Co3O4/OPAC and Co3O4 catalysts. These results highlight the synergistic effects of Ni and Co species, along with the unique properties of the OPAC support, which contribute to the enhanced activity, stability, and electron transfer characteristics of the Ni–Co3O4/OPAC hybrid. Furthermore, the improved electrical conductivity of the Ni–Co3O4/OPAC hybrid makes it a promising candidate for applications in metal-air batteries and other energy conversion devices. The utilization of waste orange peel as a carbon precursor and the facile synthesis method demonstrate the potential for cost-effective and sustainable electrocatalyst production. Overall, the Ni–Co3O4/OPAC hybrid represents a significant advancement in electrocatalyst design and holds promise for advancing the field of energy conversion and storage.

Self-Organized Integrated Electrocatalyst on Oxygen Conversion for Highly Durable Zinc-Air Batteries.

Efficient bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are key for clean energy applications such as rechargeable metal-air batteries. Highly efficient bifunctional electrocatalysts have been the focus of great attention by scientists. Here, an innovative and continuous growth method is established to fabricate integrated Janus structure Co3O4/CoNGDY catalyst, which can work for bifunctional oxygen catalytic conversion, achieving highly durable zinc-air batteries. Embedded in the hydrangea-shaped N-doped graphdiyne (NGDY), the Co3O4/CoNGDY is self-organized by CoNGDY at the NGDY contact sites and Co3O4 at the upper part, in which Co3O4 works as OER catalyst and CoNGDY acts as ORR catalyst. Due to the incomplete charge transfer within integrated structure, NGDY reduces the d-band center of the Co sites, so the adsorption strength of intermediates is balanced, and the catalytic activity for ORR/OER is increased. The Co3O4/CoNGDY can serve as an efficient air electrode of rechargeable zinc-air batteries. The rechargeable Co3O4/CoNGDY-based aqueous zinc-air batteries demonstrate excellent performance with a high specific capacity of 746.8 mAh g-1 and an extremely long lifetime of more than 5000 hours. The recoverable modularized cylindrical Co3O4/CoNGDY-based solid-state zinc-air batteries with a power density of up to 167.6 mW cm-2 can be achieved.

Interfacial Effects of NiFe-Based Bifunctional Electrocatalysts for Highly Efficient Overall Water Splitting.

The reasonable design of highly efficient NiFe-based bifunctional electrocatalysts is imperative for water splitting and alleviation of the energy crisis. Herein, the NiFe-based bifunctional electrocatalysts are designed and grown in situ on Ni foam by a simple hydrothermal method. The interfacial effect among NiFe-LDH, Fe5O7(OH), and NiFe2O4 exposes more catalytic active sites, modulated electronic structure, and optimization of the electrocatalytic performances. The overpotentials of NiFe-LDH/Fe5O7(OH)/NiFe2O4/NF-15h (NFN/NF-15h) for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are 78 and 208 mV at 10 mA cm-2, respectively. Overall water splitting can drive 10 mA cm-2 with a cell voltage of only 1.538 V. This work contributes a feasible idea for the design and synthesis of NiFe-based bifunctional electrocatalysts with outstanding water splitting performance.

Se-Doped CoS2@MoS2 Heterostructures on Multiwalled Carbon Nanotubes as Efficient Bifunctional Electrocatalysts for Alkaline Overall Water Splitting.

The use of efficient and affordable non-precious metal catalysts for hydrogen and oxygen evolution reactions is vital for replacing and widely implementing new energy sources. Nevertheless, improving the catalytic performance of these non-precious-metal bifunctional electrocatalysts continues to be a major challenge. In this article, an optimized Se-incorporated bulk CoS2@MoS2 heterostructure grown on the surface of carbon nanotubes is reported. The resulting Se-CoS2@MoS2/CNTs exhibit robust bifunctional electrocatalytic performance, with low overpotentials of 85 and 240mV @ 10 mA·cm-2 for HER and OER, respectively. The materials exhibit superior long-term stability of over 145h, surpassing most electrocatalysts of similar type. This enhanced performance is attributed to the synergistic effect at the interface between the MoS2 and CoS2 phases, abundant active sites, and high active surface area, which collectively improves the electron-transfer efficiency during the reaction process. Furthermore, the incorporation of the amorphous state of Se into the heterostructure yields a change in the crystallinity of the heterostructure in the electronic structure, which optimizes the adsorption and activation energy barriers of the catalytic intermediate. This study thus presents a promising approach to regulating anion doping in bifunctional electrocatalysts.

In Situ Construction of Perovskite Pr0.5Ba0.5Mn0.8Co0.1Ru0.1O2.5+δ/CoRu Nanoparticles with Co-N-C Composite Enabling Efficient Bifunctional Electrocatalyst for Zinc-Air Batteries.

Bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential components of rechargeable zinc-air batteries. In this study, we synthesized a Pr0.5Ba0.5Mn0.8Co0.1Ru0.1O2.5+δ (PBMCRO) perovskite composite with in situ exsolved CoRu nanoparticles and Co-N-C, functioning as an efficient bifunctional electrocatalyst for zinc-air batteries. The in situ exsolution of CoRu nanoparticles from the perovskite oxide was facilitated by the reducing action of 2-methylimidazole (2-MIM). Concurrently, Co-N-C was used to decorate PBMCRO, forming a novel bifunctional composite electrode of Co-N-C-PBMCRO. The incorporation of CoRu nanoparticles introduces a significant number of electrochemically active oxygen vacancies in the perovskite matrix, enhancing ORR and OER performance. Additionally, the Co-N-C synergistically improves electrochemical activity while preserving the structural stability of the perovskite oxide. The prepared Co-N-C-PBMCRO catalyst demonstrates significantly enhanced bifunctional performance compared to the undecorated pristine perovskite Pr0.5Ba0.5MnO3-δ (PBMO). The zinc-air battery with Co-N-C-PBMCRO catalyst achieve a peak power density of approximately 90 mW/cm2 and exhibit remarkable cycling stability for 788 h. This study presents a novel and effective strategy to enhance the catalytic performance of perovskite-based air electrodes for rechargeable metal-air batteries.

Partial Selenization Strategy for Fabrication of Ni0.85Se@NiCr-LDH Heterostructure as an Efficient Bifunctional Electrocatalyst for Overall Water Splitting.

NiCr-LDH and its partial selenization as Ni0.85Se@NiCr-LDH heterostructure is established here as an alkaline water electrolyzer for achieving enhanced overall water splitting efficiency. The hydrothermally synthesized optimized batch of Ni0.85Se@NiCr-LDH is thoroughly characterized to elucidate its structure, morphology, and composition. Compared to pristine NiCr-LDH, the batch of Ni0.85Se@NiCr-LDH exhibits exceptional alkaline OER and HER activity with low overpotentials of 258 and 85 mV at 10 mA cm-2, respectively. Besides, Ni0.85Se@NiCr-LDH also exhibits excellent acidic HER with an overpotential of only 61 mV at 10 mA cm-2, indicating that Ni0.85Se@NiCr-LDH can operate effectively across a wide pH range. The excellent electrochemical stability of Ni0.85Se@NiCr-LDH for 24 h operation is attributed to the formation of a thin layer of SeOx during OER operation. The role of selenization and the effect of Cr in the LDH lattice toward enhanced electrocatalytic water splitting is discussed. The outstanding OER and HER performances of Ni0.85Se@NiCr-LDH are attributed to the higher electrochemical active surface area, favorable conditions for adsorption of HER/OER intermediates, low charge transfer resistance, and improved conductivity. The practical application ofNi0.85Se@NiCr-LDHas a bifunctionalelectrocatalyst for overall water splitting is reflected from the low cell voltage of 1.548 V at 10 mA cm-2.

Enhanced Electrocatalytic Capacity of Two POM@NH2‐MIL‐101(Fe) Composites for Oxygen Evolution Reaction

AbstractThe development and exploration of efficient bifunctional electrocatalysts for water splitting are in high demand and have garnered significant attention in recent years. Herein, by incorporating the advantages of catalytically active polyoxometalates (POMs) and structural stable metal–organic frameworks (MOFs), two POM@MOFs composite materials, Ni4Mo12@Fe and Co4Mo12@Fe, have been successfully prepared via the encapsulation of POMs anions, [MoV12O30(μ2‐OH)10H2{NiII4(H2O)12}]∙14H2O (noted as Ni4Mo12) and [MoV12O30(μ2‐OH)10 H2{CoII(H2O)3}4]∙12H2O (noted as Co4Mo12), into the cavities of MOFs NH2‐MIL‐101(Fe), respectively. Compared to each individual components, Ni4Mo12@Fe and Co4Mo12@Fe composites, as heterogeneous electrocatalysts, both showed enhanced electrocatalytic capacities for efficient oxygen evolution reaction (OER) under alkaline conditions with overpotentials of 332.64 mV for Ni4Mo12@Fe and 352.64 mV for Co4Mo12@Fe at 10 mA cm−2. Additionally, the enhanced electrocatalytic capacities of these two composites could also achieve towards hydrogen evolution reaction (HER). Such a POMs‐assisted strategy for the formation of POM@MOFs composites, described here, paves a new avenue for the development of highly economical, active nonnoble metal bifunctional electrocatalysts for OER and HER.

Structural and Phase Engineering of a Hierarchical 2D-2D Nickel MOF/Hydroxide-Derived Ni0.85Se/NiTe2 Heterointerface for Robust HER, OER, and Overall Water Splitting.

The development of a nonnoble metal-based cost-effective, efficient, and durable bifunctional electrocatalyst is crucial to achieving the goal of carbon neutrality. In this study, a structural and interfacial engineering approach is employed to design a 2D-2D hierarchical nickel MOF/nickel hydroxide-derived nickel selenide/nickel telluride dual-phase material through a single-step selenotellurization process. The rational design of highly ordered nanoarchitectures provides well-defined voids and ample pathways for ion diffusion. Furthermore, hierarchical nickel selenide/nickel telluride works synergistically at heterojunctions, providing a local ion enrichment mechanism for the catalytic process. As a result, Ni0.85Se/NiTe2@Ni-NH@CC needs an overpotential of 69 and 240 mV to deliver a current density of 10 mA cm-2 for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, with an outstanding stability observed for over 100 h. Moreover, the Ni0.85Se/NiTe2@Ni-NH@CC (+, -) device exhibits excellent overall water-splitting performance with a cell voltage of 1.50 V at 10 mA cm-2 and can be operated steadily for >100 h at 100 mA cm-2. Density functional theory (DFT) calculations indicate favorable kinetics for H-adsorption at the selenotelluride heterojunction, thereby promoting the HER. This work highlights a new approach for designing a unique nanoarchitecture of MOF/hydroxide-derived selenotelluride heterojunctions for high-efficiency energy conversion applications.

Bamboo-derived aerogel with atomically dispersed Co as a high-performance bifunctional electrocatalyst for durable zinc-air batteries

The development of highly efficient and durable bifunctional electrocatalysts is crucial for rechargeable zinc-air batteries, which have garnered significant attention as a promising sustainable energy storage technology. Herein, a novel Co-N-C-1050 catalyst is synthesized using a high-temperature gas transport method, where high purity cobalt powder and bamboo biomass aerogel are treated with ammonia gas at 1050 °C. The resulting catalyst exhibits a 3D interconnected porous network composed of dense carbon fibers, which atomically dispersed Co, N, and C elements are uniformly distributed. The synergistic integration of highly active Co single atoms and N-doped 3D carbon fiber aerogel enables Co-N-C-1050 to demonstrate excellent bifunctional electrocatalytic performance for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), comparable to commercial Pt/C and RuO2 catalysts. This catalyst has a half-wave potential of 0.842 V for ORR and a potential of 1.472 V at 10 mA cm−2 for OER, outperforming N-C-1050 and benchmark catalysts. A zinc-air battery is driven by Co-N-C-1050 achieves a high power density of 135 mW/cm2 and exceptional stability over 138 h of charge/discharge cycling, surpassing the higher-cost Pt/C + RuO2 catalyst. This biomass aerogel based single-site Co-N-C catalyst offers a promising approach for developing high-efficiency and long-cycle-life zinc-air batteries.

N/S‐codoped Nickel oxide supported on activated Montmorillonite clay as an Efficient Bifunctional Electrocatalyst for Overall Water Splitting

Developing low‐cost, highly effective, and durable electrocatalysts for complete water splitting (OER/HER) is crucial for future energy provision. Herein, we report N/S‐codoped Nickel oxide supported on activated Montmorillonite clay as an efficient bifunctional electrocatalyst for water electrolysis. The different wt% of Ni‐MMT catalysts were synthesized using an effortless one‐step solvothermal method and their phase recognition, morphology, analysis of elements, and electrochemical performance were confirmed by various characterization techniques. The optimal 10 Ni‐MMT catalyst exhibits outstanding efficiency in both HER (170 mV) and OER (365 mV) at a current density of 10 mAcm‐2 in 1M KOH. Furthermore, doping of N/S heteroatoms increases the active sites for HER/OER, facilitates charge transfer and achieves electrochemical stability of 15 h. The Ni‐MMT catalyst achieved an overall water‐splitting performance in 1M KOH, reaching 10 mAcm‐2 at a cell voltage of 1.82 V.

Mo-doped CoFe-layered double hydroxides as an efficient bifunctional electrocatalyst for overall water splitting: Effects of different molybdenum additions on catalytic performance

The layered double hydroxides (LDHs) electrocatalysts have emerged as promising electrocatalysts for electrolytic water splitting due to their simple synthesis, high activity. However, traditional LDH-based catalysts face the low electrical conductivity and durability under electrolysis conditions. In this work, Mo–CoFe LDH was prepared by a two-step hydrothermal method, and the effect of different molybdenum content on its catalytic performance was studied. Among them, the OER and HER properties of Mo-CoFe LDH-1 are better than those of non-Mo doping. Mo–CoFe LDH-1 has the low HER and OER overpotentials are 192 mV and 134 mV, respectively at 10 mA cm−2. In addition, using Mo–CoFe LDH-1 for water splitting can achieve a low voltage of 1.55 V at 10 mA cm−2, and it also showed a good stability within 100 h. The excellent properties of Mo–CoFe LDH-1 is mainly due to the formation of 3D nanoflower structure and the doping of Mo element in CoFe LDH, significantly adjusting its electronic structure. This work is of great significance for the design of bifunctional LDHs-based electrocatalysts.

Redox Activity of Co Species in the Active Sites of CoNx/CoOx Facilitates Oxygen Electrocatalysis for Zn-Air Batteries.

Developing efficient bifunctional oxygen electrocatalysts is crucial for enhancing the performance of rechargeable Zn-air batteries (ZABs). In this study, cobalt/cobalt oxides embedded in N-doped carbon nanofibers (Co/CoOx/NCNFs) were synthesized through a combination of electrospinning and annealing processes. The resulting Co/CoOx/NCNFs catalysts feature abundant CoNx and CoOx active species, leveraging the large specific surface area of nanofibers to facilitate oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The optimized Co/CoOx/NCNFs-0.1 achieved a half-wave potential (vs. RHE) of 0.82 V and required only 429 mV to reach 10 mA cm-2 in a typical three-electrode system with 0.1 M KOH using an electrochemical workstation equipped with a pine instruments rotator, outperforming the Pt/C+RuO2. The assembled ZABs exhibited high specific capacity (771 mAh gZn -1), substantial power density (981.6 mWh gZn -1), and long-term stability (>325 h). In situ Raman spectroscopy confirmed that the electrocatalytic processes involve the redox activity of Co (II and III) species derived from abundant CoNx and CoOx, elaborating the origin of the catalysts' exceptional oxygen electrocatalysis performance. This work not only presents a straightforward and effective approach for producing bifunctional oxygen electrocatalysts in ZABs but also sheds light on the catalytic mechanisms underlying ORR and OER for CoNx/CoOx-based oxygen electrocatalysts.

Self-supported nanoflower-like CoNiSe2/NF as an efficient bifunctional electrocatalyst

Designing affordable, high-efficiency bifunctional electrocatalysts is essential for renewable energy systems. In this study, by a simple hydrothermal reaction and subsequent low-temperature selenisation, nickel-cobalt composite selenides CoNiSe2/NF loaded on nickel foam were obtained, which CoNiSe2/NF exhibited a nanoflower-like structure, which provided abundant ligand-active sites for trapping the catalytic intermediates, accelerated the charge transport, and formed an optimised interface. When used in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), the CoNiSe2/NF electrocatalysts exhibited excellent catalytic activity and durability. Under alkaline conditions, the overpotentials for HER and OER were determined to be 152 mV and 290 mV, at a current density of 10 mA cm−2. All the results may be attributed to the synergistic effect between the transition metals, the great specific surface area of tip-rich nanoflower-like structures rich in tip effects, and the selenium-modulated electronic structure together. An effective method for developing bifunctional electrocatalysts is demonstrated in this study.

Decrypting Synergy of Alloy & Metal Nanoparticles Within Nitrogen-Doped Carbon Nanosheets for Zn-Air Batteries with Ultralong Cycling Stability.

The exploration of efficient, robust, and low-cost bifunctional electrocatalysts to drive the commercial application of Zn-air batteries (ZABs) is of great significance but still remains a challenge. Herein, a 1D coordination polymer (1D-CP) derived FeNi alloy & Co nanoparticles (NPs) co-implanted N-doped carbon nanosheets (FNC/NCS) is judiciously crafted and employed as a high-performance electrocatalyst for ultralong lifetime ZABs. The key to this strategy is the leveraging of metal-coordinated melamine to direct the pyrolysis of 1D-CP, enabling the in situ formation of well-dispersed FeNi alloy and Co NPs within the carbon matrix. The resulting FNC/NCS exhibits prominent oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity with a small overall oxygen potential difference (ΔE = 0.68V). Density functional theory (DFT) simulation demonstrates that the synergistic effect between FeNi alloy and Co NPs can reduce energy barriers, promote electron transfer, and optimize the formation of crucial intermediates, thereby largely boost ORR/OER activity of FNC/NCS. The FNC/NCS-assembled ZABs possess high specific capacity, large power density, and ultralong cycling life in both aqueous (> 3300h) and solid-state (150h) electrolytes. This work provides a viable strategy for 1D-CP-derived bifunctional electrocatalysts and dissects the synergistic effect between different metal species, affording significant guidance for the development of renewable energy materials.

Highly efficient bifunctional electrocatalyst for rechargeable zinc-air batteries: N, S dual-doped carbon encapsulating sulfur vacancy-rich FeCo/Fe-CoS nanoparticles

In this research, we present a highly efficient bifunctional electrocatalyst, N, S dual-doped carbon framework encapsulating sulfur vacancy-rich FeCo/Fe-CoS nanoparticles (VS-FeCo/Fe-CoS/NSC), synthesized via co-precipitation, sequential pyrolysis and sulfidation process. The prepared electrocatalyst exhibits exceptional performance in oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and rechargeable Zn-air batteries (ZABs). The VS-FeCo/Fe-CoS/NSC-based ZAB demonstrates outstanding bifunctionality, exhibiting high specific capacity of 793 mAh gZn−1 and peak power density of 164.68 mW cm−2. These values surpass those of noble metal-based ZAB, highlighting the superior electrochemical performance of the VS-FeCo/Fe-CoS/NSC catalyst. Such superior activity stems from synergistic effect of abundant heterointerfaces and sulfur vacancies in FeCo/Fe-CoS structure, resulting in enhanced charge transfer efficiency and reaction kinetic performance. Furthermore, the encapsulation of nanoparticles within the heteroatom-doped carbon matrix prevents aggregation and dissolution of active species, ensuring long-term stability during the battery operation. The electrochemical reversibility and stability of VS-FeCo/Fe-CoS/NSC are confirmed through extensive cycling tests, highlighting its potential for practical applications in energy conversion and storage systems.

Simple solution immersion for realizing bifunctional catalyzation of water splitting in various electrolytes

Developing cost-effective, highly efficient and scalable bifunctional electrocatalysts for hydrogen production is crucial for advancing hydrogen energy systems. However, current methods are hindered by high energy consumption and material limitations. This work introduces a bifunctional electrocatalyst (NiFe-OH@Co2P@NF), by simply immersing a hierarchical cobalt phosphide electrode in mixed Ni/Fe solution, followed by forming layered nickel-iron hydroxides on the surface. Electrochemical tests reveal that this catalyst enhances active site exposure, accelerates electron transfer, and significantly lowers the overpotential for water electrolysis. It requires minimal overpotentials (79 mV at 10 mA cm−2, 175 mV at 150 mA cm−2) in 1 M KOH solution. In a dual-electrode electrolytic cell system, the catalyst enables efficient hydrogen production at a current density of 10 mA cm−2 with just 1.52 V, demonstrating robust stability during prolonged alkaline water splitting tests. Moreover, the bifunctional electrodes display good performance and durability in simulated alkaline seawater and 1 M KOH + seawater.

Development of an efficient bifunctional electrocatalyst based on Co/CoSe2 nanoparticles embedded in N, Se co-doped carbon for AEMFC and rechargeable Zn-air battery

We suggest a hollow-structured N, Se dual-doped carbon framework embedded with Co/CoSe2 nanoparticles (Co/CoSe2@NSeC) as highly efficient bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The prepared electrocatalyst exhibits high electrochemical active surface area attributed to its unique hollow/porous structure and defective heteroatom doping sites. Furthermore, the strongly coupled heterojunction between Co and CoSe2 species not only provides abundant and highly active sites but also generates built-in electric field, thereby promoting electron transfer during the electrocatalytic reaction. Based on the above considerations, the prepared catalyst shows excellent bifunctional electrocatalytic performance. Leveraging the excellent ORR activity of Co/CoSe2@NSeC, alkaline exchange membrane fuel cells (AEMFC) with the Co/CoSe2@NSeC as air cathode exhibits high power density of 171.23 mW cm2. Furthermore, the rechargeable Zn-air battery employing the Co/CoSe2@NSeC shows high specific capacity (729.4 mAh gZn−1), peak power density (192.88 mW cm2), and sustained stability over 300 cycles.

NiO/ATO as an efficient bifunctional electrocatalysts for oxygen evolution and urea oxidation reactions

In this study, Ni-MOF-derived NiO was mixed with various weights of commercial antimony-doped tin oxide (ATO) using a simple and efficient hydrothermal method to synthesize composites denoted as AN-1, AN-2, and AN-3, which were subsequently characterized using a variety of physicochemical methods. The as-prepared materials were used as bifunctional electrocatalysts for oxygen evolution reaction (OER) and urea oxidation reaction (UOR). In the UOR, the AN-1 electrocatalyst exhibited excellent performance compared to the other electrocatalysts. In a 1.0 M KOH aqueous electrolyte, the OER onset potential was approximately 1.64 V, whereas, in the UOR, the overpotential was 1.38 V (vs RHE), which is lower than that of the OER. The AN-1 electrocatalyst showed lower Tafel slope values in both the OER and UOR studies: 173 mV dec−1 and 109mV dec−1, respectively.

Tailoring the Heterointerfaces of Earth-Abundant Transition-Metal Nanoclusters on Nickel Oxide Nanosheets for Enhanced Overall Water Splitting through Electronic Structure Optimization.

Evolving highly competent and economical electrocatalysts for alkaline water electrolysis is crucial in renewable hydrogen energy technologies. The slow hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) kinetics under alkaline electrolytes, still, has troubled developments in high-performance green hydrogen production systems. Herein, we demonstrate the tailoring of the interface of earth-abundant transition-metal nanoclusters (MNCs), including iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) nanoclusters on nickel oxide nanosheets (M NCs|NiO NS) through metal-support interaction for enriched overall water splitting under an alkaline electrolyte. The strong metal-metal oxide interaction allows alteration of the binding capabilities of hydrogen ions (*H) and hydroxyl ions (*OH) on Ni electrodes. Specifically, the robust interaction between Fe and NiO reveals optimized binding of H* and OH* energies, facilitating the water-splitting reaction under an alkaline electrolyte. In addition, the improved HER/OER catalytic activity is attained with the Fe NCs|NiO NS with small overpotentials of ∼62.0 and ∼380.0 mV for the HER and OER, respectively, a high mass activity of ∼90.0 A g-1, a turnover frequency of ∼5.94 s-1, and long-lasting stability via offering abundant electrochemical active sites, three-dimensional (3D) morphologies, and high dispersion of nanoclusters that provide effective charge and mass transport processes. This study provides a promising strategy for the effective design of efficient bifunctional electrocatalysts based on earth-abundant materials for alkaline water electrolyzers.

Regulating the electronic structure of nickel phosphides via interface engineering and molybdenum doping boosts benzyl alcohol oxidation coupled with hydrogen production

Coupling the electrocatalytic benzyl alcohol oxidation reaction (BAOR) with hydrogen evolution reaction (HER) presents a favorable energy conversion method. However, the development of highly efficient bifunctional electrocatalysts poses significant challenges. In this study, a Mo doped biphasic Ni2P-Ni12P5 heterostructure (Mo-Ni2P/Ni12P5@NF) has been developed to serve as the efficient bifunctional electrocatalyst. The Mo-Ni2P/Ni12P5@NF resulted in exceptional activities for both the BAOR and HER. The electrolyzer cell using Mo-Ni2P/Ni12P5@NF as anode and cathode operates at an impressively low cell voltage of merely 1.38 V to achieve the current density of 10 mA cm−2 in a benzyl alcohol-containing aqueous solution. Experimental results and density functional theory (DFT) calculations indicate that the introduction of Mo can significantly modulate the electronic structure of Ni-based phosphide catalysts and adjust for the d-band center of the active Ni sites. This modulation significantly optimizes the adsorption capabilities for both benzyl alkoxide (Ph-CH2O-) and the H* intermediates on Mo-Ni2P/Ni12P5@NF, thereby increasing electrocatalytic activity toward BAOR and HER respectively. Our work offers a valuable insight into designing bifunctional electrocatalysts and highlights the potential of Mo doping systems to produce hydrogen and value-added products efficiently.