Enhanced bifunctional aspects of oxygen vacancy rich cation substituted MnCo2O4 intercalated with g-C3N4 as an oxygen evolution and supercapacitor electrode

Rational design of electrocatalyst for oxygen evolution reaction (OER) to efficiently evolve oxygen molecules with low overpotential and electrode material disclosing high power density for supercapacitor remains a challenge. Pristine g-C₃N₄, MnCo₂O₄/g-C₃N₄ and cation modified MnCo₂O₄ intercalated with g-C₃N₄ (Mn_0·4Ni_0·6Co₂O₄/g-C₃N₄) were prepared and investigated its efficacy towards catalyzing OER. Mn_0.4Ni_0.6Co₂O₄/g-C₃N₄ electrocatalyst exhibits a low overpotential of 320 mV @ current density of 10 mA/cm² and a small Tafel slope of 75.2 mV/dec. It follows simultaneous evolution of oxygen from oxyhydroxide species during the electrocatalytic performance. The same electrocatalyst also reveals excellent stability during its long term operation. Simultaneously, the same material discloses elevated specific capacitance of 1987.2 F/g at 1 A/g and a maximum retention of capacitance even after its cycling for 8000 cycles than pristine g-C₃N₄ and MnCo₂O₄/g-C₃N₄ composite. This observation greatly insists that Mn_0·4Ni_0·6Co₂O₄/g-C₃N₄ composite can be employed as an electrode material for high performance supercapacitors due to its excellent capacitance and outstanding cycling stability.     

Co3O4@g-C3N4 supported on N-doped graphene as effective electrocatalyst for oxygen reduction reaction

Oxygen reduction reaction (ORR) is a key component of numerous energy conversion equipment, including metal-air batteries and fuel cells. Reasonably designing high-efficiency non-noble materials as ORR electrocatalysts is crucial for large-scale practical applications. In this work, a calcination-hydrothermal method is used to prepare Co₃O₄@g-C₃N₄ (g-C₃N₄ wrapped Co₃O₄ nanoparticle) supported on nitrogen doped graphene (NG). The electrochemical activity of composites is estimated by cyclic voltammograms and linear sweep voltammetry in 0.1 M KOH medium. Owing to the positive synergistic role stemming from the Co₃O_4, g-C₃N₄, Co-N_x effective sites and N modified graphene in the composite material, the Co₃O₄@g-C₃N₄/NG owns positive onset potential of 0.920 V (vs. RHE) and half-wave potential of 0.846 V (vs. RHE), which are superior to onset potential of 0.917 V and half-wave potential of 0.824 V for commercial Pt/C, respectively. Additionally, it also exhibits longer-term stability and stronger methanol resistance comparing with Pt/C. The nonprecious metal catalyst could be used as a hopeful catalyst to substitute commercial Pt/C for ORR.     

Co–Co3O4 nanostructure with nitrogen-doped carbon as bifunctional catalyst for oxygen electrocatalysis

In view of the development of advanced bi-functional oxygen electrodes for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), herein, we report the synthesis of Co–Co₃O₄ nanostructure encased in N-doped carbon (Co–Co₃O₄/NC) by carbothermal reduction followed by controlled oxidative treatment. The formation of a protective-active oxide layer on the metallic-Co not only facilitated the effective charge separation and transport but also displayed improved stability of Co–Co₃O₄/NC in an alkaline operating condition. The Co–Co₃O₄/NC catalyst afforded 0.810 V overvoltage between ORR and OER in 0.1 M KOH solution, consequently, this lower reversible overvoltage would result in energy saving of around 0.246 V if Co–Co₃O₄/NC is used as an oxygen electrode instead of commercially available 40 wt % Pt/C. Furthermore, in comparison with the use of Pt/C + IrO₂ as an ORR and OER catalyst, respectively the single bi-functional electrocatalyst i.e., Co–Co₃O₄/NC would result in energy saving of around 0.13 V.     

Zn-substituted MnCo2O4 nanostructure anchored over rGO for boosting the electrocatalytic performance towards methanol oxidation and oxygen evolution reaction (OER)

Mixed valence spinel oxides have emerged as an attractive and inexpensive anode electrocatalyst for water oxidation to replace noble metals based electrocatalysts. The present work demonstrates the facile synthesis of Zn substituted MnCo₂O₄ supported on 3D graphene prepared by simple hydrothermal technique and its application as an electrocatalyst for water oxidation and methanol oxidation. The physico-chemical properties of the nanocatalyst were studied using various microscopic, spectroscopic and diffraction analyses confirming the formation of the composite. The electrocatalytic performance of the prepared electrocatalyst was evaluated using potentiodynamic, potentiostatic and impedance techniques. The synthesized Zn_1-xMn_xCo₂O₄/rGO electrocatalyst with x = 0.2 and 0.4 offered the same onset potential and overpotential at 10 mA/cm². However, catalyst x = 0.4 delivered a higher current density indicating the superiority of the same over other compositions which is attributed to better kinetics that it possessed for OER as revealed by the smallest Tafel slope (80.6 mV dec⁻¹). The prepared electrocatalysts were tested for methanol oxidation in which electrocatalyst Zn_1-xMn_xCo₂O₄/rGO with x = 0.4 shows a better electrochemical performance in oxidizing methanol with the higher current density of 142.3 mA/cm². The above catalyst also revealed excellent stability and durability during both MOR and OER, suggesting that it can be utilized in practical applications.     

Encapsulated spinel CuXCo3-XO4 in carbon nanotubes as efficient and stable oxygen electrocatalysts

The development of efficient, stable and cost-effective electrocatalysts for oxygen reduction reactions (ORR) and oxygen evolution reactions (OER), have become one of the most important bottlenecks in pursuing emerging renewable energy storage and environment friendliness technologies. In this study, we have successfully developed encapsulated Cu_XCo_3-XO₄ spinel nanocrystals in carbon nanotubes as high-performance bifunctional oxygen electrocatalyst by one-step hydrothermal reaction. As compared with other Co-based materials, the resulting Cu_XCo_3-XO₄@C composite presents excellent catalytic performance and outstanding stability for both OER and ORR with ultralow overpotential (η = 0.358 V) at a current density of 10 mA/cm² and half-wave potential (E_1/2 = 0.82 V) in alkaline solution, respectively. The developed strategy to encapsulate spinel into carbon nanomaterials via a controllable pathway, may open new opportunities for the encapsulation structures of other catalysts.     

Synthesis and characterization of nickel oxide/cobalt oxide nanocomposite for effective degradation of methylene blue and their comparative electrochemical study as electrode material for supercapacitor application

In this paper, we have synthesized a nanocomposite of nickel oxide (NiO) and cobalt oxide (Co₃O₄) using l-ascorbic acid which is named A(NC). Herein, A stands for l-ascorbic acid, N stands for nickel oxide (NiO), and C stands for cobalt oxide (Co₃O₄). Where l-ascorbic acid has been used as stabilizing agent/capping agent. Herein, a simple two steps wet-chemical method has been used for the synthesis of the nanocomposite A(NC). This synthesized nanocomposite has been characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), UV–visible spectroscopy, and Fourier transform infrared spectroscopy (FTIR). A comparative electrochemical study has been done using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) techniques for supercapacitor performance. This study has been performed with a three-electrode system using 1 M Na₂SO₄ as a supporting electrolyte. Herein, a glassy carbon electrode (GCE) as a working electrode, Ag/AgCl as a reference electrode and Pt electrode as a counter electrode have been used in the electrochemical analysis. The CV curves have been recorded at different scan rates of 5 mV/s, 10 mV/s, 15 mV/s, 20 mV/s, 40 mV/s, 80 mV/s, and 100 mV/s respectively. The value of specific capacitance has been calculated 2.1472 F/g at 5 mV/s and energy density at 0.1074 Wh/kg using the CV curves. Whereas, specific capacitance and energy density have been determined 0.6833 F/g and 0.0342 Wh/kg respectively using the GCD method. Also, the photocatalytic degradation behavior of the synthesized nanocomposite A(NC) has been investigated against methylene blue (MB) dye. Herein, 89.88% MB dye has been degraded with synthesized nanocomposite A(NC) within 360 min in the presence of sunlight.     

Oxygen vacancy-based ultrathin Co3O4 nanosheets as a high-efficiency electrocatalyst for oxygen evolution reaction

Enhancing the catalytic activity of Co₃O₄ electrocatalysts featuring abundant oxygen vacancies is required to enable their application in oxygen evolution reaction (OER). However, developing a harmless defect engineering strategy based on mild conditions to realize such an enhancement remains a challenge. Here, ultrathin Co₃O₄ nanosheets with abundant oxygen vacancies were prepared through a simple two-step method comprising a hydrothermal process and pre-oxidation to study the catalytic activity of the nanosheets toward OER. The ultrathin sheet structure and the Co₃O₄ nanosheets surface provide abundant active sites. The oxygen vacancy not only improves the catalyst activity, but also improves the electron transfer efficiency. These advantages make ultrathin Co₃O₄ nanosheets with abundant oxygen vacancies an excellent electrocatalyst for oxygen evolution. In an alkaline medium, ultrathin Co₃O₄ nanosheets exhibited excellent OER catalytic activity, with a small overpotential (367 mV for 10 mA/cm²) and faster reaction kinetics (65 mV/dec).Moreover, the electrocatalyst still maintained 68% of its original catalytic activity after 24 h operation. This work provides an extensive and reliable method for the preparation of low-cost and highly efficient OER electrocatalysts.     

Modification of the ultrasonication derived-g-C3N4 nanosheets/quantum dots by MoS2 nanostructures to improve electrocatalytic hydrogen evolution reaction

In this work, graphitic carbon nitride (g-C₃N₄) nanosheets/quantum dots (NS/QD) was prepared using a simple and low-cost procedure. By two steps exfoliation in a bath and tip sonicator, the g-C₃N₄ (NS/QD) was produced from bulk g-C₃N₄. To improve electrocatalytic hydrogen evolution reaction (HER), the g-C₃N₄ (NS/QD) were modified by the MoS₂ nanostructures. Nanocomposite of the g-C₃N₄ (NS/QD) with MoS₂ nanostructures was deposited on a flexible, conductive and three dimensional carbon cloth by a facile and binder-free electrophoretic technique. This electrode exhibited a Tafel slope of 88 mV/dec and an overpotential of 0.28 V vs RHE at −2 mA/cm², lower than that of the g-C₃N₄, and good stability after 1000 cycles and 100 days for HER. The enhanced electrocatalytic performance was attributed to the MoS₂ and g-C₃N₄ nanostructures on three dimensional carbon cloth, leading to high surface area and more number of the exposed active sites for HER. This heterostructure improved charge transport, proton adsorption and hydrogen evolution on the electrode. This work proposes cost-effective, stable and three dimensional g-C₃N₄ based electrode for hydrogen evolution reaction.     

PANI-modified Pt/Na4Ge9O20 with low Pt loadings: Efficient bifunctional electrocatalyst for oxygen reduction and hydrogen evolution

Exploring cost-effective electrocatalysts for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) have been a goal in the sustainable hydrogen-based society. Although abundant of alternative materials have been developed, Pt/C remains the most efficient electrocatalyst for the ORR and HER. Nevertheless, improving the stability and reducing Pt loading for Pt-based electrocatalysts are still big challenges. Herein, semiconductor crystals Na₄Ge₉O₂₀ with richer topology structure was chosen as electrocatalyst support, subsequently, the conductive polymer polyaniline (PANI) was decorated on semiconductor Na₄Ge₉O₂₀, low-content Pt nanoparticles (Pt NPs) with the size of 1–3 nm were then uniformly anchored on the surface of Na₄Ge₉O₂₀-PANI to obtain the efficient bifunctional electrocatalyst for ORR and HER in the acidic solution. More importantly, the stability and mass activity of the obtained electrocatalyst 5 wt% Pt/Na₄Ge₉O₂₀-PNAI are significantly higher than that of commercial 20 wt% Pt/C for ORR and HER. It was proposed that the PANI could not only promote the electron transfer from Na₄Ge₉O₂₀ to Pt, but also stabilize the Pt NPs, thus, improving the electrocatalytic activity and stability of 5 wt% Pt/Na₄Ge₉O₂₀-PNAI.     

In situ synthesis of CoFe2O4 nanoparticles embedded in N-doped carbon nanotubes for efficient electrocatalytic oxygen reduction reaction

The development of electrocatalyst possessing superior oxygen reduction reaction (ORR) activity is highly desirable due to the low sluggish kinetics at the cathode of fuel cell. Here, CoFe₂O₄ nanoparticles embedded in N-doped carbon nanotubes electrocatalyst (denoted as CoFe₂O₄-NC) is synthesized via polymerization of pyrrole, absorbing metal ion and annealing under Ar/NH₃ atmosphere. By in situ integrating the catalytically active CoFe₂O₄ nanoparticles with the N-doped carbon nanotubes and enhancing electrical conductivity, the as-obtained electrocatalyst exhibits excellent ORR activity and long-term stability with a half-wave potential of 0.86 V and 10 h continuous cycling, outperforming the reported similar catalysts. This work opens a new path for the expansion of low cost and efficient ORR electrocatalysts to substitute Pt-based metals for energy storage and conversion devices.     

Zeolitic-imidazolate frameworks-derived Co3S4/NiS@Ni foam heterostructure as highly efficient electrocatalyst for oxygen evolution reaction

Transition metals sulfide-based nanomaterials have recently received significant attention as a promising cathode electrode for the oxygen evolution reaction (OER) due to their easily tunable electronic, chemical, and physical properties. However, the poor electrical conductivity of metal-sulfide materials impedes their practical application in energy devices. Herein, firstly nano-sized crystals of cobalt-based zeolitic-imidazolate framework (Co-ZIF) arrays were fabricated on nickel-form (NF) as the sacrificial template by a facile solution method to enhance the electrical conductivity of the electrocatalyst. Then, the Co₃S₄/NiS@NF heterostructured arrays were synthesized by a simple hydrothermal route. The Co-ZIFs derived Co₃S₄ nanosheets are grown successfully on NiS nanorods during the hydrothermal sulfurization process. The bimetallic sulfide-based Co₃S₄/NiS@NF-12 electrocatalyst demonstrated a very low overpotential of 119 mV at 10 mA cm^?2 for OER, which is much lower than that of mono-metal sulfide NiS@NF (201 mV) and ruthenium-oxide (RuO₂) on NF (440 mV) electrocatalysts. Furthermore, the Co₃S₄/NiS@NF-12 electrocatalyst showed high stability during cyclic voltammetry and chronoamperometry measurements. This research work offers an effective strategy for fabricating high-performance non-precious OER electrocatalysts.     

Nitrogen doped graphene quantum dots (N-GQDs)/Co3O4 composite material as an efficient bi-functional electrocatalyst for oxygen evolution and oxygen reduction reactions

In this work, a facile development of a bi-functional electrocatalyst for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is reported. A composite material comprising of tiny particles of nitrogen doped graphene quantum dots (N-GQDs) embedded into cobalt oxide (Co₃O₄) flakes is prepared by sodium borohydride reduction method and followed by annealing at 600 °C under inert atmosphere. Structural, morphological and crystalline features are analyzed using FESEM, TEM, HRTEM, XRD and XPS studies. Moreover, optical and fluorescence properties of N-GQDs are studied using UV–visible and fluorescence spectroscopic techniques. These studies clearly reveal and confirm the formation of a composite material. Further electrochemical characteristics toward OER and ORR are investigated by using linear sweep voltammetry (LSV) and cyclic voltammetry (CV) techniques. Compared to the individual entities of pure Co₃O₄ and N-GQDs alone, the electrocatalytic activity of N-GQDs/Co₃O₄ composite material is significantly higher towards ORR. Similarly, the same composite material is also used as an electrocatalyst for OER in 0.1 M KOH aqueous electrolyte and it exhibits a lower overpotential of 330 mV to obtain a current density of 10 mA/cm² along with higher electrocatalytic activity and the reason is mainly attributed to the synergistic effect between N-GQDs and Co₃O₄. Thus, N-GQDs/Co₃O₄ composite material is demonstrated to be a high performance bi-functional electrocatalyst for ORR and OER.     

Flower-shaped and sea urchin-shaped structures coexisting in cobalt-based phosphate and oxides achieve efficient electrochemical overall water electrolysis

Active site engineering for electrocatalysts is an essential strategy to improve their intrinsic electrocatalytic capability for practical applications and it is of great significance to develop a new excellent electrocatalyst for overall water splitting. Here, Co₃O₄/nickel foam (NF) and Co₂(P₄O₁₂)/NF electrocatalysts with flower-shaped and sea urchin-shaped structures are synthesized by a simple hydrothermal process and followed by a post-treatment method. Among them, Co₂(P₄O₁₂)/NF shows good catalytic activity for hydrogen evolution reaction (HER), and at the current density of 10 mA cm^?2, the overpotential is only 113 mV Co₃O₄/NF exhibits good catalytic activity for oxygen evolution reaction (OER), and the overpotential is 327 mV at 20 mA cm^?2. An alkaline electrolyzer with Co₃O₄/NF and Co₂(P₄O₁₂)/NF catalysts respectively as anode and cathode displays a current density of 10 mA cm^?2 at a cell voltage of 1.59 V. This work provides a simple way to prepare high efficient, low cost and rich in content promising electrocatalysts for overall water splitting.     

Electrodeposited graphene hybridized graphitic carbon nitride anchoring ultrafine palladium nanoparticles for remarkable methanol electrooxidation

Exploiting high performance electrocatalysts is crucial for the effective electrooxidation of methanol, although some barriers exist. Herein, we develop a hybrid support composed of graphitic carbon nitride (g-C₃N₄) and reduced graphene oxide (rGO) synergistically anchoring sufficient ultrafine palladium (Pd) nanoparticles via a simple one-step electrodeposition technique. The morphology and structure were characterized by scanning/transmission electron microscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy, which confirmed that the Pd nanoparticles were massively and uniformly dispersed on the support of g-C₃N₄@rGO with a the average particle size of 5.87 nm, deriving from the nitrogen in g-C₃N₄ contributing to the electron transport highway on the rGO nanosheet layer surface. Furthermore, electrochemical results suggested that the Pd/g-C₃N₄@rGO showed a high electrocatalytic efficiency for methanol oxidation with a high current density reached 0.131 mA cm⁻². Based on a novel approach to the g-C₃N₄@rGO hybrid nanostructure, this work offers a promising method for the design and synthesis for the superior performance methanol electrocatalyst.     

Single transition metal atom anchored on g-C3N4 as an electrocatalyst for nitrogen fixation: A computational study

Electrocatalytic nitrogen reduction reaction (NRR) provides a green and sustainable way to produce ammonia at ambient conditions. The key to realize highly efficient NRR is the catalysts. To design highly active electrocatalysts for NRR, the multistep mechanism involved in NRR must be clearly unraveled. Herein, single V atoms anchored on g-C₃N₄ is identified to be an efficient electrocatalyst for NRR by screening single 3d transition metal (TM = Sc to Zn) atoms anchored by g-C₃N₄ (TM@g-C₃N₄) through density functional theory calculations. NRR takes place on V@g-C₃N₄ preferentially through distal path with a relatively low limiting potential of ?0.55 V. The outstanding NRR performance of V@g-C₃N₄ is found from the peculiar electronic structure of V after anchored in the six-fold cavity of g-C₃N₄ and the good transmitter role of V for electron transfer between N_xH_y species and g-C₃N₄. Moreover, the formation energy and dissolution potential indicate that V@g-C₃N₄ is thermodynamically and electrochemically stable and the aggregation of V atoms is unfavorable thermodynamically, signifying that the synthesis of V@g-C₃N₄ is feasible in experiments. Our work screens out a superior noble metal-free NRR electrocatalyst and will be helpful for the development of ambient artificial nitrogen fixation.     

Co0.85Se on three-dimensional hierarchical porous graphene-like carbon for highly effective oxygen evolution reaction

Designing an efficient, cheap and abundant catalyst for oxygen evolution reaction (OER) is crucial for the development of sustainable energy sources. A novel catalyst which could be a promising candidate for such electrocatalysts is described. Co_0.85Se supported on three-dimensional hierarchical porous graphene-like carbon (HPG) exhibits outstanding catalytic performances for OER in alkaline medium. It is found that the onset overpotential is 311 mV on the Co_0.85Se/HPG electrode, which is more 28 and 41 mV negative than that on the Co/HPG and Co₃O₄/HPG electrodes. What's more, the value of Tafel slope is 61.7 mV dec⁻¹ and the overpotential at the current density of 10 mA cm⁻² is 385 mV on this electrode. The Co_0.85Se/HPG of this work is an appealing electrocatalyst for OER in basic electrolyte.     

Molecule-confined modification of graphitic C3N4 to design mesopore-dominated Fe-N-C hybrid electrocatalyst for oxygen reduction reaction

To design inexpensive carbon catalysts and enhance their oxygen reduction reaction (ORR) activity is critical for developing efficient energy-conversion systems. In this work, a novel Fe-N-C hybrid electrocatalyst with carbon nanolayers-encapsulated Fe₃O₄ nanoparticles is synthesized successfully by utilizing the molecular-level confinement of graphitic C₃N₄ structures via hemin biomaterial. Benefiting from the Fe-N structure prevalent on the carbon nanosheets and large mesopore-dominated specific surface area, the synthesized catalyst under optimized conditions shows excellent electrocatalytic performance for ORR with an E_ORR at 1.08 V versus reversible hydrogen electrode (RHE) and an E_1/2 at 0.87 V vs. RHE, and outstanding long-term stability, which is superior to commercial Pt/C catalysts (E_ORR at 1.04 V versus RHE and E_1/2 at 0.84 V versus RHE). Moreover, the low hydrogen peroxide yield (<11%) and average electron transfer number (~3.8) indicate a four-electron ORR pathway. Besides, the maximum power density of the home-made Zn-air battery using the obtained catalyst is 97.6 mW cm⁻². This work provides a practical route for the synthesis of cheap and efficient ORR electrocatalysts in metal-air battery systems.     

Enhanced electrochemical activity of Co3O4/Co9S8 heterostructure catalyst for water splitting

The dearth of efficient, robust, and economical electrocatalysts for water oxidation is dubiously the key obstacle for renewable energy devices, so synthesis of efficient, and cost-effective metal-based water oxidation catalysts is vital. Herein, Co₃O₄, Co₉S₈ catalysts and their heterostructure Co₃O₄/Co₉S₈ were synthesized and evaluated as water oxidation electrocatalysts. The characterization of Co₃O₄, Co₉S₈, and Co₃O₄/Co₉S₈ electrocatalysts was performed using Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction techniques. The heterostructure Co₃O₄/Co₉S₈ (1.46 V) exhibited water oxidation electrocatalysis at extremely low onset potential compared to Co₃O₄ (1.58 V), and Co₉S₈ (1.48 V) catalysts. A 281 mV overpotential required to attain a current density of 50 mA cm^?2 in alkaline solution (1 M KOH), outperforming most of Co-based benchmark electrocatalysts. Further, the Co₃O₄/Co₉S₈ heterojunction demonstrated catalytic activity with small Tafel slope of 37 mV dec^?1. The finding of electrochemical studies involving controlled potential electrolysis and long-term stability are projected to steer the future advancement in constructing efficient, economical, stable, and earth-abundant metal-based water oxidation catalysts.     

A glassy carbon electrode modified with tailored nanostructures of cobalt oxide for oxygen reduction reaction

Herein we report on various surface morphological characteristics of the synthesized cobalt oxide (Co₃O₄) nanostructures obtained by means of facile one-step hydrothermal method for oxygen reduction reaction (ORR). The synthesized nanostructures of Co₃O₄ were adequately characterized by field emission scanning electron microscopy (FESEM) fitted with Energy-dispersive X-ray spectroscopy (EDX) elemental mapping, X-ray diffraction (XRD) and Raman techniques. The electrochemical studies were carried out to analyse the performance of as-synthesized catalysts for ORR by cyclic voltammetry (CV), and chronoamperometric (CA) techniques. A higher electrocatalytic response was observed for Co₃O₄ nanocubes compared with all the other controlled electrodes by CV with a current density of 0.69 mA/cm² at a potential value of −0.46 V. The as-synthesized material showed adequate tolerance against methanol observed by CV in the presence of 0.5 M methanol, and good stability when compared with commercial Pt/C catalyst using the CA technique.     

Highly efficient ternary CuP2/Ni1−xCux‒P@g-C3N4 nanostructure for improved hydrogen and oxygen evolution reactions

Herein, a highly active, and stable copper phosphide/nickel-copper phosphide (CuP₂/NiCuP) nanosheet supported by a g-C₃N₄ is constructed via phosphorization for hydrogen and oxygen evolution reactions (HER and OER, respectively). Strong coupling between CuP₂/NiCuP heteronanosheets and the structured g-C₃N₄ provides CuP₂/NiCuP/g-C₃N₄ with a regulated electronic state, sufficient anchored active sites, reduced mass transport distance, and improved structural stability. Consequently, the obtained CuP₂/(NiCu)_1:1P/g-C₃N₄ electrocatalyst manifests excellent performance in HER and OER, with overpotentials of 96 and 280 mV at 10 mA cm⁻², respectively, as well as stability. The excellent HER and OER activities are mainly ascribed to the collective effects of electronic structure engineering, strong interaction between CuP₂ and NiCuP in the heteronanojunction, abundant catalytic active sites, and highly conductive g-C₃N₄ support. This study provides novel insights for designing cost-effective bimetallic alloy-phosphide HER/OER electrocatalysts for various sustainable energy-conversion applications.