Bifunctional Electrocatalysts Research Articles

Heterogeneous Ni-Boride/Phosphide Anchored Amorphous B-C Layer for Overall Water Electrocatalysis.

The rational design of efficient and economical bifunctional electrocatalysts remained a challenge for overall water electrolysis. In this work, the Ni-boride/ phosphide particles anchored amorphous B-doped carbon layer with hierarchical porous characteristics in Ni foam (Ni3P/Ni3B/B-C/NF) was fabricated for overall water splitting. The Boroncarbide (B4C) power was filled and fixed in the NF interspace through the electroplating and electroless plating, and then annealed in vacuum high temperature. The amorphous B-C layer derived from the B4 C not only speeded up the electron transport, but also cooperate with Ni-boride/phosphide to enhance the electrocatalytic activity for HER and OER synergistically. Furthermore, the hierarchical porous architecture of Ni3P/Ni3B/B-C/NF increased space utilization to load more active materials. The self-supported Ni3P/Ni3B/B-C/NF electrode possessed a low overpotential of 212 and 280 mV to deliver 100 mA cm-2 for HER and OER, respectively, and high stability for 48 h. In particular, the electrolyzer constituted with the Ni3P/Ni3B/B-C/NF bifunctional electrocatalyst only required a voltage of 1.59 V at 50 mA cm-2 for water electrocatalysis under alkaline medium, and demonstrated long-term stability for 48 h. This study provides a new technical path for the development of bifunctional of transition metal borides to promote the application of hydrogen production from water splitting.

Electron Manipulation and Surface Reconstruction of Bimetallic Iron-Nickel Phosphide Nanotubes for Enhanced Alkaline Water Electrolysis.

Developing high-efficiency and stable bifunctional electrocatalysts for water splitting remains a great challenge. Herein, NiMoO4 nanowires as sacrificial templates to synthesize Mo-doped NiFe Prussian blue analogs are employed, which can be easily phosphorized to Mo-doped Fe2xNi2(1-x)P nanotubes (Mo-FeNiP NTs). This synthesis method enables the controlled etching of NiMoO4 nanowires that results in a unique hollow nanotube architecture. As a bifunctional catalyst, the Mo-FeNiP NTs present lower overpotential and Tafel slope of 151.3 (232.6) mV at 100 mA cm-2 and 76.2 (64.7) mV dec-1 for HER (OER), respectively. Additionally, it only requires an ultralow cell voltage of 1.47 V to achieve 10 mA cm-2 for overall water splitting and can steadily operate for 200 h at 100 mA cm-2. First-principles calculations demonstrate that Mo doping can effectively adjust the electron redistribution of the Ni hollow sites to optimize the hydrogen adsorption-free energy for HER. Besides, in situ Raman characterization reveals the dissolving of doped Mo can promote a rapid surface reconstruction on Mo-FeNiP NTs to dynamically stable (Fe)Ni-oxyhydroxide layers, serving as the actual active species for OER. The work proposes a rational approach addressed by electron manipulation and surface reconstruction of bimetallic phosphides to regulate both the HER and OER activity.

A Bifunctional Electrocatalyst of Flower-Like Cr-Doped CoP/Fe2P Microsphere for Efficient Overall Water Splitting

Abstract Developing efficient, low-price non-noble metal-based electrocatalysts for overall water splitting in alkaline medium remains a formidable challenge. In our work, Cr-doped CoP/Fe2P (Cr-CoP/Fe2P) flower-like microsphere was synthesized through a simple hydrothermal and phosphating process. The resulting Cr-CoP/Fe2P electrocatalyst shows significantly enhanced oxygen evolution reaction performance (262 mV @ 10 mA cm-2) and has a satisfactory hydrogen evolution reaction performance (114 mV @ 10 mA cm-2), coupled with favorable stability in an alkaline medium. Furthermore, when assembling Cr-CoP/Fe2P into an electrolytic cell, the two-electrode system can provide a current density of 10 mA cm-2 at a voltage of 1.61 V. At high current density, the performance of the electrolytic cell composed of Cr-CoP/Fe2P is superior to that of noble metal catalyst electrode pair. Electronic structure analysis and various characterizations confirm that Cr doping and the formation of CoP/Fe2P heterogeneous interfaces redistribute the electron densities of the active sites, enlarge the specific surface area, and enhance the aerophobicity of the catalysts, thereby improving the electrocatalytic property. This work provides a referable method for engineering highly efficient and stable non-noble polymetallic phosphides, which serve as bifunctional electrocatalyst for overall water splitting.

Efficient Hydrogen Evolution Electrocatalyst: MoN/Ni3N/NF Coupled with Methanol Oxidation Reaction for Formate Production in Alkaline Media

Abstract Electrocatalytic water splitting for hydrogen production is promising, but its practical application is limited by the sluggish kinetics of the anodic oxygen evolution reaction (OER) and the less valuable oxygen by-product. Hence, replacing OER with a thermodynamically favorable methanol oxidation reaction (MOR) and coupling with value-added formate generation on the anode is an energy-saving and effective scheme. In this work, we report a self-supporting bifunctional electrocatalyst MoN/Ni3N/NF, which exhibits excellent hydrogen evolution reaction catalytic activity and stability, requiring overpotentials of only 18 and 68 mV to reach current densities of −10 and −100 mA cm−2, respectively. Moreover, the catalyst’s performance minimally deteriorates after long-standing chronopotentiometry measurements (−100 mA cm−2@150h). When MOR is used instead of OER, the required potential drops by 200 mV to 1.38 V at a current density of 100 mA cm−2 and MoN/Ni3N/NF also demonstrates splendid catalytic stability towards OER and MOR. Finally, a two-electrode system employing MoN/Ni3N/NF as a bifunctional electrocatalyst only requires a cell voltage of 1.40, 1.68 V to achieve current densities of 10 and 100 mA cm−2, respectively. The coupled electrolyzer also exhibits high faradaic efficiency for producing cathodic H2 (100%) and anodic formate (90%).

Iron Triad-Based Bimetallic M–N–C Nanomaterials as Highly Active Bifunctional Oxygen Electrocatalysts

Iron Triad-Based Bimetallic M–N–C Nanomaterials as Highly Active Bifunctional Oxygen Electrocatalysts

Electron and surface engineering of Ni2P/MnP4 heterojunction as high performance bifunctional electrocatalyst for amperage-level overall water splitting

Producing hydrogen through electrocatalytic overall water splitting with ampere-level current density is still limited by the high cost and poor stability of electrocatalysts. In this work, a new type Ni2P/MnP4 heterojunction composite material was designed and prepared as bifunctional electrocatalyst. Based on XPS spectra and theoretical calculation, the formation of Ni2P/MnP4 heterojunction successfully modulates the local electronic structure of Ni2P and enhances the ionization of H and Ni by increasing the electron transfer rate. Moreover, the special nanovilli structure and superhydropholic/superaerophobic surface of Ni2P/MnP4 heterojunction accelerates the transfer of electrolyte and gaseous products. Benefiting from these advantages, the as-prepared Ni2P/MnP4/CF not only exhibits superior electrocatalytic performance, which can release 10 mA/cm2 current density with a low overpotential of 69 mV and 247 mV for HER and OER respectively, but also shows admirable stability of continuous overall water splitting to drive 1000 mA/cm2 for 180 h without notable activity degradation. We believe this material possesses outstanding potential for industrial applications, and our strategy may provide a new pathway to design relative materials.

Superhydrophilic/superaerophobic CoP/CoMoO4 multi-level hierarchitecture electrocatalyst for urea-assisted hydrogen evolution reaction in alkaline media

Utilizing the thermodynamically favorable urea oxidation reaction instead of the anodic oxygen precipitation reaction is an alternative pathway for the energy-saving hydrogen production. Therefore, it is significant to explore advanced electrocatalysts for both HER and UOR. In this work, a dendritic heteroarchitectures of 2D CoMoO4 nanosheets deposited on 1D CoP nanoneedles (CoP/CoMoO4-CC) was fabricated as bifunctional electrocatalyst. 1D CoP nanostructure with fast charge transport pathways and 2D CoMoO4 nanostructure with large specific surface area and short paths for electron/mass transport. The unique morphology endows the superhydrophilic and superaerophobic properties, allowing for the rapid contact with the reactants and rapid removal of surface-generated gases. As a result, the CoP/CoMoO4-CC shows efficient bifunctional activity. This work offers a new avenue to rationally design bifunctional electrocatalysts for large-scale practical hydrogen production.

Vertically Staggered Porous Ni2P/Fe2P Nanosheets with Trace Ru Doping as Bifunctional Electrocatalyst for Alkaline Seawater Splitting

AbstractDesigning a bifunctional electrocatalyst with high performance and low‐cost is of great significance to promote the large‐scale application of water splitting. Herein, porous Ru‐Ni2P/Fe2P heterojunction nanosheets with a vertically staggered structure are rationally fabricated to boost alkaline seawater splitting under large current densities. The Ru‐Ni2P/Fe2P catalyst exhibits remarkable activity in alkaline media, requiring only 274 and 331 mV at a large current density of 1000 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Additionally, the NiFeOOH layer formed on the surface of Ru‐Ni2P/Fe2P is proposed as the active phase to promote the OER performance. Furthermore, an anion exchange membrane (AEM) electrolyzer assembled by Ru‐Ni2P/Fe2P electrocatalyst exhibits excellent long‐term durability over 100 h, achieving a current density of 500 mA−2 at 2.0 V in alkaline seawater at 60 °C. Theoretical calculations reveal that the Ni2P/Fe2P heterojunction integration with trace Ru leads to balanced adsorption and desorption properties. Moreover, the active sites of Ru‐Ni2P/Fe2P are confirmed, in which Ni site is favorable for HER and Fe site is conducive to OER. This work provides an insight into designing a highly efficient and cost‐effective bifunctional electrocatalyst for overall seawater splitting.

Developing energy-efficient nitrate-to-ammonia flow cells with bifunctional NiFeW-oxide thin-film electrodes made by magnetron sputtering technique

Herein, we develop a sputtered NiFeW-oxide thin-film bifunctional electrocatalyst with the incorporated oxygen vacancies and multivalent cations of Ni2+/3+, Fe2+/3+, and W6+ to enhance the economic viability of electrocatalytic nitrate reduction for commercial applications. Our NFW-0.5 achieves a notable 54.6 mg/h.cm2 ammonia yield rate at a modest applied potential of −0.2 V vs. RHE, coupled with an outstanding Faradaic efficiency of 93.7%. Furthermore, our NFW-0.5(+)‖NFW-0.5(−) flow-cell electrolyzer with a larger electrode of 2×2 cm2 reveals an impressive ammonia productivity of 143.5 mg/h.cm2 at a cell voltage of 2.0 V, accompanied by a superior Faradaic efficiency of 96.1%, an energy efficiency of 26%, and a low energy consumption of 26.3 kWh/kg.NH3. An oxygen vacancy-based NO3-pinned mechanism is proposed to explain our excellent nitrate reduction. Our work introduces a new paradigm to design efficient and bifunctional electrocatalysts for potential industrial-scale ammonia production.

Anion substitution-induced CuCoSe hollow nanotubes as multifunctional electrode materials for supercapacitors and overall water splitting

Developing highly efficient non-noble-metal electrode materials for energy storage and conversion is crucial for advancing sustainable and renewable energy. In this study, a facile and effective anion substitution-induced approach was designed to synthesize uniform CuCoSe hollow nanotubes. Impressively, the obtained CuCoSe hollow nanotubes reach an exceptional mass-specific capacitance of 2,853.1F·g−1 at 10 A·g−1, with intriguing rate capability and desirable capacitance retention after 5,000 cycles. The assembled CuCoSe//CuCoSe symmetrical supercapacitor device exhibits a high energy density of 218.9 Wh·kg−1 at a power density of 4,000 kW·kg−1. Furthermore, the CuCoSe hollow nanotubes show exceptional performances in both oxygen and hydrogen evolution reactions, necessitating low overpotentials of 94.4 and 33.4 mV at 10 mA·cm−2. When used as a bifunctional electrocatalyst, the assembled CuCoSe||CuCoSe electrolytic cell affords a low cell voltage of 1.40 V to drive 10 mA·cm−2, significantly superior to other commercial electrolyzers and most reported bifunctional electrocatalysts. Experimental and density functional theory calculations suggest that selenides substituted CuCo-layered double hydroxides can greatly enhance the electrochemical performances. This work will be beneficial for the design of the next generation of energy storage and conversion technologies.

Bifunctional mechanism of oxygen evolution reaction and oxygen reduction reaction induced by surface reconstruction in Perovskite electrocatalysts

Elucidation of the relationship among crystal structure, material compositions, and electrocatalytic performance is beneficial to the design of electrocatalysts with high activity. Specially, for bifunctional electrocatalysts, there is a lack of the unified understanding of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) mechanisms. Based on the first-principles calculations, LaCoO3 surface reconstructions with different OH coverage under OER/ORR condition are determined. Thereby, the different reaction pathways for OER and ORR with the cooperation of Co and O sites are revealed, under which Co and lattice O sites are activated dynamically, and an overpotential of 0.35 V for the OER and 0.44 V for the ORR are obtained. Furthermore, the octahedra lattice distortion-related bifunctional mechanism (DRBM) is proposed from electron structure analysis, and the bifunctional activity of different B-site doped LaCoO3 (LaCoMO3) are studied. Based on this mechanism, we find that OER, ORR, and their bifunctional activity of LaCoMO3 all exhibit a volcano trend as a function of the O-B-O bond angle formed by Co and lattice oxygen. Consequently, we predict that Mn, Cr, Fe, and Ti doped LaCoO3 electrocatalysts exhibit remarkable bifunctional activity, which is corroborated by the reported experimental results.

Design and Development of Sustainable Cu2 (II)- and Mn2 (III)-Embedded Bifunctional Electrocatalysts: Enhanced Hydrogen and Oxygen Generation.

Nowadays, environmentally friendly, low-cost-effective, and sustainable electrocatalysts used widely for hydrogen and oxygen evolution reactions have come into the limelight as a new research topic for scientists. This study highlights the preparation of two unique and symmetrical dinuclear Cu (II) and Mn (III) bifunctional catalysts by a facile simple slow evaporation and diffusion route. [C32H24Cu2F4N4O4] (1) and [C32H24Mn2F4N4O4] (2) both have monoclinic (C2/c (15)) crystal systems, with oxidation states +2 and +3, respectively. Prominent SPR peaks at 372 and 412 nm indicate an M-L charge transfer transition in both complexes. The synthesized electrocatalysts display exceptional catalytic activity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Complex 1 exhibits enhanced hydrogen generation in 0.5 M H2SO4 with a small overpotential of 216 mV at -10 mA cm-2 along with a significantly lower Tafel value of 97 mV/dec compared to Complex 2. Moreover, Complex 1 is highly active for the OER in 1 M KOH with a small Tafel slope of 103 mV/dec and a low overpotential of 340 mV to acquire 10 mA cm-2 current density, compared to Complex 2. Complex 1 and Complex 2 remain stable up to 20 h in acidic electrolyte and up to 36 h and 20 h in the basic electrolyte, respectively.

FeNi alloy embedded in three-dimensional nitrogen-doped porous carbon as bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries

Iron‑nickel (FeNi) alloy is one of the efficient bifunctional oxygen electrocatalysts for zinc-air batteries (ZABs). However, FeNi alloy nanoparticles prepared by traditional synthesis strategies are easy to agglomerate and have non-uniform sizes, which is not conducive to the improvement of catalytic activity and stability. Here, we have successfully encapsulated two different kinds of nitrogen-rich metal phthalocyanines (MPcs) in situ doping in zeolitic imidazolate framework (ZIF-8) homogeneously by the “double solvents” method. The ligand nitrogen and macrocyclic structure of MPcs encapsulated in ZIF-8 not only helps metal dispersion and enhances the metal-ligand‑nitrogen (M-Nx) structure, but also enhances the graphitisation of three-dimensional (3D) porous carbon after pyrolysis. Thus, a FeNi alloy uniformly embedded in 3D nitrogen-doped porous carbon materials (FeNi@NC) was constructed in the subsequent pyrolysis process and used as an efficient bifunctional oxygen reduction/evolution (ORR/OER) electrocatalyst for rechargeable ZABs. Impressively, the FeNi@NC catalyst carries high half-wave potential (0.850 V) in ORR and the low overpotential (291 mV) in OER, significantly better than Pt/C (0.830 V) and RuO2 (307 mV), respectively. In addition, the rechargeable ZAB assembled with FeNi@NC air cathode has a specific capacity of 649 mW cm−2 and shows no significant degradation after 240 h of charging and discharging cycles. This study provides a new design idea for the manufacture of carbon-supported non-noble metal alloy catalysts with bifunctional oxygen catalytic activity, and verifies the feasibility of regulating the composition of non-noble metals to construct a rechargeable ZABs with excellent performance.

Value‐Added Cascade Synthesis Mediated by Paired‐Electrolysis Using an Ultrathin Microenvironment‐Inbuilt Metalized Covalent Organic Framework Heterojunction

AbstractEnergy‐saving and value‐added management in advanced catalysis is highly desirable but is challenged by the limitations of multifunctional catalysts and catalytic modules. Herein, an azo‐linked phthalocyanine‐porphyrin covalent organic framework (COF) with the ultrathin layered nanostructure grown on carbon nanotubes (NiPc‐azo‐H2Pp@CNTs) has been designed and synthesized, which can serve as a highly active and stable bifunctional heterojunction electrocatalyst for selective paired‐electrosynthesis through coupling anodic iodide oxidation reaction and cathodic CO2 conversion. Particularly, the inbuilt local microenvironment conferred by the dihydroporphyrin moieties in COF can act as a proton reservoir to promote the proton relay at the heterojunction interface during the electrocatalytic process. Moreover, through the cascade construction of dual electrocatalytic/organocatalytic modules, the cathode‐generated CO can be further converted to dimethyl carbonate with a yield of 6.21 mmol L−1 h−1, while the anode‐produced iodine can be derived into iodoform on the hundred‐milligram scale. It is worth noting that the value‐added cascade synthesis mediated by paired‐electrolysis using the distinctive and high‐powered electrocatalysts will help advance the sustainable development of industrial intelligent manufacturing.

Controllable Regulation of the Oxygen Redox Process in Lithium-Oxygen Batteries by High-Configuration-Entropy Spinel with an Asymmetric Octahedral Structure.

Designing bifunctional electrocatalysts to boost oxygen redox reactions is critical for high-performance lithium-oxygen batteries (LOBs). In this work, high-entropy spinel (Co0.2Mn0.2Ni0.2Fe0.2Cr0.2)3O4 (HEOS) is fabricated by modulating the internal configuration entropy of spinel and studied as the oxygen electrode catalyst in LOBs. Under the high-entropy atomic environment, the Co-O octahedron in spinel undergoes asymmetric deformation, and the reconfiguration of the electron structure around the Co sites leads to the upward shift of the d-orbital centers of the Co sites toward the Fermi level, which is conducive to the strong adsorption of redox intermediate LiO2 on the surface of the HEOS, ultimately forming a layer of a highly dispersed Li2O2 thin film. Thin-film Li2O2 is beneficial for ion diffusion and electron transfer at the electrode-electrolyte interface, which makes the product easy to decompose during the charge process, ultimately accelerating the kinetics of oxygen redox reactions in LOBs. Based on the above advantages, HEOS-based LOBs deliver high discharge/charge capacity (12.61/11.72 mAh cm-2) and excellent cyclability (424 cycles). This work broadens the way for the design of cathode catalysts to improve oxygen redox kinetics in LOBs.

A facile dual isolation and protection strategy for preparation of PtFe intermetallic compound in biomass-derived carbon with high activity and durability for pH-universal bifunctional electrocatalysts

A facile dual isolation and protection strategy is developed to prepare PtFe intermetallic electrocatalyst (PtFe–N–C@bioC) on porous biomass carbon (bioC) derived from peanut shell. In preparation, meso-tetraphenylporphyrine (H2TPP) together with platinum (II)-tetraphenylporphyrin (PtTPP) are in-situ fabricated on the porous peanut shell-derived bioC matrixes and then further absorbed Fe (III) tetraphenyl porphyrin (FeTPP) molecules through π−π interactions between PtTPP/H2TPP and FeTPP to form a mixed precursor of FeTPP/PtTPP/TPP-bioC. Upon pyrolysis of FeTPP/PtTPP/TPP-bioC, PtFe bimetallic-containing N-doped carbon formed on bioC (PtFe–N–C@bioC). The resultant PtFe–N–C@bioC showed excellent oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) activity across a wide pH range. In particular, under alkaline medium, PtFe–N–C@bioC shows the ORR performance with an onset potential (Eonset) of 0.989 V, a half-wave potential (E1/2) of 0.901 V and a limiting current density (JL) of −6.214 mA cm−2. Meanwhile, PtFe–N–C@bioC delivers an enhanced mass activity (1.197 A mg−1Pt), which is 13 times larger than commercial Pt/C. For HER, PtFe–N–C@bioC shows an impressive overpotential (η10) of 17 mV at a current density of 10 mA cm−2 under acidic medium. Further, it is applied to Zn-Air batteries with a power density performance of 98.7 mW cm−2 and good durability.

Sustainable energy generation: High-performance NiCo2S4@S-g-C3N4 bifunctional electrocatalyst advances water splitting efficiency

Efforts to create cost-effective electrocatalysts from abundant materials, for the utilization of water electrolysis reactions, are viewed as promising sources for sustainable clean energy generation. This article describes the synthesis of cobalt sulphide (CoS) nanoparticles using a straightforward and environmentally friendly one-pot hydrothermal process. The series of nickel-doped CoS (NiCo2-x S4) introduced with varying the weight percentage of Ni (1, 2, 4, 8, 6, and 10 wt%), and the composite Ni-dopped CoS on varying the weight percentage (10, 30, 50, 70, and 90 wt %) of sulfur-doped graphitic carbon nitride (NiCo2S4@S-g-C3N4) was created. Utilizing X-ray diffraction analysis (XRD), EDS, FTIR, and scanning electron microscopy (SEM) synthesized electrocatalysts were characterized. Doped with Fluorine After being changed with an electrocatalyst, tin oxide was used as the working electrode to monitor the electrochemical activity of the whole water splitting process using chronopotentiometry, cyclic voltammetry (CV), linear sweep voltammetry (LSV), and EIS. NiCo2S4@S-g-C3N4 exhibited higher electrocatalytic performance with an overpotential 370 mV for OER and 415 mV for HER at the current intensity of 10 mAcm−2. Transition metal sulfide electrocatalysts exhibit good electrolytic performance, due to their high surface areas and intrinsically high catalytic activity. These findings suggest that the NiCo2S4@S-g-C3N4 composite possesses a significant role for use in energy conversion and energy storage applications.

NiMn layered double hydroxides with promoted surface defects as bifunctional electrocatalysts for rechargeable zinc–air batteries

Layered double hydroxides (LDHs) are attractive bidimensional materials for electrochemical applications because of their high activity in the oxygen evolution reaction (OER). However, their limited bifunctionality due to the slow kinetics of the oxygen reduction reaction (ORR) is a bottleneck for their use in secondary Zn-air batteries (ZABs). In this work, cobalt-free NiMn LDHs were rationally designed by optimizing the Ni composition and incorporating surface defects onto the LDH (oxygen vacancies, Ov) while performing interface engineering using a carbonaceous support enriched with nitrogen heteroatoms. The LDHs without induced defects presented the optimal activity for the OER at a 3:1 Ni/Mn atomic ratio (onset potential 1.47 V vs. 1.45 V for IrO2/C), while the ORR was unfavorable. However, the further optimization by introducing Ov and N–heteroatoms (labeled as Ov-NiMn LDH/NCNTG) allowed bifunctionality by improving the onset potential to 0.90 V while decreasing the half-wave potential difference from 180 mV for the material without induced defects to 100 mV, and by improving the limiting current density by a factor of two. In this regard, density of states (DOS) calculations suggested that surface defects improved the electronic transfer while decreasing the oxygen adsorption energy. ZAB tests indicated that the interface-engineered material allowed a battery voltage of 1.47 V, and a power density of 64 mW cm−2. The battery also maintained stability over 180 charge/discharge cycles at 10 mA cm−2 (50 h), with ΔV below 150 mV between the initial and final cycles.

Mo-doped SrCo0.5Fe0.5O3-δ perovskite oxides as bifunctional electrocatalysts for highly efficient overall water splitting

Perovskite oxides with high electrocatalytic activities and cost-effectiveness can be developed by rational doping. Here, we fabricate a series of perovskite oxides comprising SrCo0.5Fe0.5-xMoxO3-δ (x = 0, 0.05, 0.10, 0.15) doped with different proportions of Fe and Mo elements to enhance the long-term stabilities and electrocatalytic activities for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Among them, SrCo0.5Fe0.4Mo0.1O3-δ (SCFM10) exhibits the optimum electrocatalytic activity for water splitting, exhibiting overpotentials at −10 mA cm−2 and 10 mA cm−2 of ∼200 mV for HER and ∼310 mV for OER, respectively, generating a current density of 10 mA cm−2 using only 1.68 V in a two-electrode electrolytic cell. Additionally, SCFM10 demonstrates outstanding stability, maintaining continuous operation for 100 h without visible decay. These results give some new points of view into the development of bifunctional catalysts for the purpose of efficient water splitting in a sensible way.

Aluminium, Nitrogen-Dual-Doped Reduced Graphene Oxide Co-Existing with Cobalt-Encapsulated Graphitic Carbon Nanotube as an Activity Modulated Electrocatalyst for Oxygen Electrocatalyst for Oxygen Electrochemistry Applications.

There is a rising need to create high-performing, affordable electrocatalysts in the new field of oxygen electrochemistry. Here, a cost-effective, activity-modulated electrocatalyst with the capacity to trigger both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in an alkaline environment is presented. The catalyst (Al, Co/N-rGCNT) is made up of aluminium, nitrogen-dual-doped reduced graphene oxide sheets co-existing with cobalt-encapsulated carbon nanotube units. Based on X-ray Absorption Spectroscopy (XAS) studies, it is established that the superior reaction kinetics in Al, Co/N-rGCNT over their bulk counterparts can be attributed to their electronic regulation. The Al, Co/N-rGCNT performs as a versatile bifunctional electrocatalyst for zinc-air battery (ZAB), delivering an open circuit potential ≈1.35V and peak power density of 106.3mWcm-2, which are comparable to the system based on Pt/C. The Al, Co/N-rGCNT-based system showed a specific capacity of 737mAhgZn -1 compared to 696mAhgZn -1 delivered by the system based on Pt/C. The DFT calculations indicate that the adsorption of Co in the presence of Al doping in NGr improves the electronic properties favoring ORR. Thus, the Al, Co/N-rGCNT-based rechargeable ZAB (RZAB) emerges as a highly viable and affordable option for the development of RZAB for practical applications.