Structure-design and synthesis of nickel-cobalt oxide/sulfide/phosphide composite nanowire arrays for efficient overall water splitting

The construction of cost-effective bifunctional electrocatalysts with the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is significant for efficient overall water splitting. Herein, this work demonstrates a novel strategy for the synthesis of nickel-cobalt oxides/sulfides/phosphides composite (denoted as NiCoO–2P/S) nanoarrays on Ni foam. In this method, Ni–Co bimetallic oxide nanowires on Ni foam were partially phosphorized and sulfurized simultaneously in situ to yield Ni–Co oxide/sulfide/phosphide composite. The NiCoO–2P/S arrays have good interfacial effects and display many holes in the nanowires, giving it the advantage of large accessible surfaces on the nanowires and a beneficial for the release of gas bubbles, resulting in an excellent OER performance with a low overpotential (η) of 254 mV at 100 mA cm^?2 and good HER activity (η₁₀ = 143 mV at 10 mA cm^?2). The electrocatalytic test results demonstrate small Tafel slopes (82 mV dec^?1 for HER, 88 mV dec^?1 for OER) and the satisfying durability in an alkaline electrolyte, indicating that the HER and OER activity was enhanced by the introduction of the Ni/Co sulfides and phosphides into Ni–Co oxides composite nanowires. Furthermore, the as-prepared NiCoO–2P/S catalyst can be used as both the anode and the cathode simultaneously to realize overall water splitting in the two-electrode electrolyzer. This system can be driven at low cell voltages of 1.50 and 1.68 V to achieve current densities of 10 and 100 mA cm^?2, respectively. This work provides an alternative strategy to prepare high-performance bifunctional electrochemical materials and demonstrates the advantages of Ni–Co oxide/sulfide/phosphide composites for water splitting.     

Preparation of Ni–P–La alloy as a novel electrocatalysts for hydrogen evolution reaction

Ternary Ni–P–La alloy was synthesized by the co-electrodeposition method on the copper substrate. The energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used for characterization of the synthesized alloy. The electrochemical performance of the novel alloy was investigated based on electrochemical data obtained from steady-state polarization, Tafel curves, linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) in alkaline solution and at ambient temperature. The results showed that the microstructural properties play a vital purpose in determining the electrocatalytic activity of the novel alloys. Also, the HER on investigated alloys was performed via the Volmer-Heyrovsky mechanism and Volmer step as RDS in this work. Ni–P–La catalyst was specified by ƞ₂₅₀ = −139.0 mV, b = −93.0 mV dec⁻¹, and j_o = −181.0 μA cm⁻². The results revealed that the Ni–P–La catalysts have a high potential for HER electrocatalysts in 1M NaOH solution.     

Synthesis,characterization and performance of a novel Ni–Co/GO-TiO2 for electrooxidation of methanol and ethanol

In order to find out electrocatalysts based on non-precious metals, Ni–Co/GO-TiO₂ composite with different amounts of nickel and cobalt is prepared and the impacts of TiO₂ nanoparticles on GO support are highlighted. Composition, morphology and textural features of the synthesized materials are characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, N₂ adsorption-desorption isotherms and field emission scanning electron microscopy equipped with energy-dispersive X-ray analysis. The electrochemical activity of the prepared catalysts toward methanol and ethanol electrooxidation in alkaline media is investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry. Results confirmed that adding TiO₂ nanoparticles to graphene oxide can increase the surface area, porosity and electrochemically active surface area of the support material. The composition with the equal amount of nickel and cobalt precursors exhibited the highest current density for methanol and ethanol electrooxiation equal to 121.07 and 145.28 mA/cm², respectively. Stability test results demonstrated that this sample maintains 94.1% and 87.5% of initial current density after 7200 s for the electrooxidation of ethanol and methanol in 1.0 M KOH, respectively. All results confirm the synergic effect of Ni and Co for the alcohols oxidation in alkaline media and equal amount of Ni and Co leads to the best catalytic performance with the highest current density, lowest impedance and maximum stability.     

Mixed metal oxides as efficient electrocatalysts for water oxidation

Water splitting is a promising reaction for storing sustainable but intermittent energies. The critical bottleneck for it is oxygen evolution reaction (OER) requiring insufficiently low overpotentials, η. Metal oxides are the group of high performance catalysts for water oxidation, so far. We report a facile synthesis of the mixed metal oxide composite (NiO/Mn-doped NiCo₂O₄) and an easy dip-coating method to create electrocatalysts on nickel foam as electrode substrates cause significant efficiency for OER. The mixed metal oxides catalyst was characterized by using electrochemical methods, high-resolution transmission electron microscopy (HR-TEM), field emission-scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), inductively coupled plasma (ICP) and fourier-transform infrared spectroscopy (FTIR). Electrocatalysts were shown a Tafel slope of 34 mV dec^?1 with overpotential η = 482 mV (for 100 mA cm^?2) and at least 20 h durable OER activity. The electrochemical data demonstrate the synergistic effect of the coupling between the three metal-centres of Ni, Co, and Mn to decline the overpotential value. The current of (OER) is related to the electrolyte pH, displaying a non-proton-concerted mechanism in an approach to identifying rate-determining steps for OER. This could be concluded by the direct neighbour lattice O^?– coupling to form an O–O bond. The simple and rapid fabrication method and the promising stability and high performance of the herein developed electrodes render them quite promising for technological water splitting systems.     

Partial phosphorization of porous Co–Ni–B for efficient hydrogen evolution electrocatalysis

Design of cost-effective and high-efficient electrocatalysts for hydrogen evolution reaction (HER) is of vital significance for the current renewable energy devices — fuel cells. Herein, we report a facile strategy to prepare partial phosphorization of Co–Ni–B material with porous structure via a water-bath boronizing and subsequent phosphorization process at moderate temperature. The optimal atomic proportion of Co to Ni is investigated via physical and electrochemical characterization. As a result, Co₉–Ni₁–B–P exhibits the best HER activity, which require an lower overpotential of ~192 mV to deliver a current density value of 10 mA cm⁻² and a smaller Tafel slope of 94 mV dec⁻¹ in alkaline media, relative to P-free Co–Ni–B catalysts, Co₉–Ni₁–B–P with other Co: Ni proportion and mono metallic borides The excellent electrocatalytic performance of Co₉–Ni₁–B–P is mainly ascribed to the three-dimensional (3D) porous structure and the coordinate functionalization between the borides and phosphides. This work provides a promising strategy for the exploration of quaternary composites as efficient and cost-effective electrocatalysts for HER.     

Cu doped Ni–Co spinel protective coatings for solid oxide fuel cell interconnects application

Four different amount of Cu doped Ni–Co alloy coatings were fabricated on SUS430 substrate by electroplating for solid oxide fuel cells (SOFCs) interconnects application. After oxidation at 800 °C, the microstructure and oxide phase of samples were tested by scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Our experimental results indicated that the Cu addition improved the electrical behavior of Ni–Co alloy coating. Cu doping reduced the activation energy (Ea) of electrons hopping and inhibited the growth of Cr₂O₃ oxide layer. Furthermore, the oxidation kinetics and electrical properties of the alloy coatings were obtained. These results showed that the 9% Cu doped Ni–Co coated steels achieved the minimum parabolic rate constant (2.05 × 10⁻¹⁴ g²cm⁻⁴s⁻¹) and area specific resistance (14.11 mΩ cm²) after the thermostatic oxidation process.     

Facile synthesis of cotton flower like Ni–Co/Ni–Co–O–P as bifunctional active material for alkaline overall water splitting and acetaminophen sensing

The development of electrode materials with simple preparation, favorable price, excellent electrocatalytic activity, and stability are some of the most important issues in the field of electrochemistry. Herein, we prepared Ni–Co/Ni–Co–O–P cotton flower like on a copper sheet (CS) by a convenient, efficient, and scalable electrodeposition method. The Ni–Co/Ni–Co–O–P was employed as effective binder free electrode material in two different applications such as electrocatalytic water splitting and acetaminophen (APAP) sensor. Remarkably, the Ni–Co/Ni–Co–O–P@CS exhibits low overpotentials of 310 and 90 mV at 10 mA cm^?2 for oxygen and hydrogen evolution reactions in alkaline media, respectively. Besides, the Ni–Co/Ni–Co–O–P@CS || Ni–Co/Ni–Co–O–P@CS couple needs a low cell voltage of 1.62 V to achieve a current density of 10 mA cm^?2, and its potential change is negligible after 20 h of continuous operation. Furthermore, Ni–Co/Ni–Co–O–P displays good electrochemical sensing performance toward APAP with a high sensitivity of 803.74 μA mM^?1cm^?2, low limit of detection of 0.16 μM, a wide linear range of 0.05 mM–3 mM, and a fast response time of 3.3 s. This work proposes a simple approach for synthesis of Ni–Co/Ni–Co–O–P as an efficient electrode material for water splitting and APAP sensing.     

The high-efficiency electrochemical catalysis of nitrogen-doped carbon nanotubes materials modified with Cu–Fe oxide alloy nanoparticles for HER and ORR

High-efficiency and economical electrocatalysts for electrochemical water splitting are the core component of the renewable energy conversion. Herein, a simple and economical strategy is described to synthesize a series of metal oxide decorated nitrogen-doped carbon nanotubes materials (N-CNT@Cu–Fe Oxide Alloy NPs) by utilizing carbon nanotubes as the substrate carrier material. Additionally, the polypyrrole (PPy) was served as both the nitrogen resource and the localizing agent to load the Cu–Fe oxide alloy. Moreover, the theoretical and test results indicated that the superior HER and ORR performance is mainly related to the synergistic effect between the nitrogen-doped CNT and metallic oxide alloy. In the series of catalysts we prepared, N-CNT@Cu₁–Fe₁ Oxide Alloy NPs exhibits more significant catalytic activity and better durability than other catalysts that we synthesized. Meanwhile, the catalyst shows the low Tafel slope of 68.28 mV dec^?1 for HER and reaches 10 mA cm^?2 at the overpotential of 375 mV. The K–L plot shows that the electron transfer number of N–CNF@Cu₁–Fe₁ Alloy NPs is 3.43.     

Tuning quaternary hybride Co–Ni–S–Se composition as a bifunctional electrocatalyst for hydrogen and oxygen evolution reactions

Developing high-efficiency and earth-abundant electrocatalysts for electrochemical water splitting is of paramount importance for energy conversion. Although tremendous effort has been paid to transition metal (TM) material-based electrocatalysts, rational design and controllable synthesis of fine structures to fully utilize the latent potential of TM materials remain great challenges. We herein report a composition-tuning strategy to achieve rational structure control of quaternary Co–Ni–S–Se materials through a facile one-pot hydrothermal method, in which earth-abundant Ni is introduced into a CoS_xSe_2-x matrix to optimize the morphology and electronic structure of the quaternary electrocatalyst. Because of the introduction of Ni, this novel Co–Ni–S–Se quaternary system shows better catalytic activity for water splitting with Tafel slopes of 42.1 mV dec⁻¹ for hydrogen evolution reaction (HER) and 65.5 mV dec⁻¹ for oxygen evolution reaction (OER), respectively, compared with its precursor Co–S–Se ternary system. For stability, there is negligible fading after long-term electrochemical test. Our work not only provides a novel thinking to introduce nickel into Co–S–Se ternary system by a facile hydrothermal synthesis for electrochemical water splitting, but also this quaternary system realizes bifunctional catalysis and better electrochemical performance relative to the ternary counterpart.     

Monodisperse Pd nanoparticles assembled on reduced graphene oxide-Fe3O4 nanocomposites as electrocatalysts for borohydride fuel cells

5 nm palladium nanoparticles (Pd NPs) are synthesized and assembled on reduced graphene oxide-iron oxide nanocomposite (rGO-Fe₃O₄) to be used in oxygen reduction reaction (ORR) and borohydride oxidation reaction (BOR) studies in alkaline media. The structure and morphology of the resulting Pd/rGO-Fe₃O₄ hybrid material are evaluated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS) analyses. The electrochemical behavior of Pd/rGO-Fe₃O₄ hybrid material for the ORR and BOR is investigated by voltammetry with rotating disk and rotating ring disk electrode and electrochemical impedance spectroscopy, enabling evaluation of the number of exchanged electrons, Tafel slope, exchange current density and activation energy. The results reveal that ORR at Pd/rGO-Fe₃O₄ proceeds as a 2-electron process with Tafel slope of 0.133 V dec^?1, while BOR proceeds as a 5.6-electron process with Tafel slope of 0.350 V dec^?1 and exchange current density of 1.38 mA cm^?2. The BOR activation energy was found to be 12.4 kJ mol^?1. Overall, this study demonstrates the good efficiency of Pd/rGO-Fe₃O₄ hybrid material for BOR.     

CoP/Ni2P heteronanoparticles integrated with atomic Co/Ni dual sites for enhanced electrocatalytic performance toward hydrogen evolution

Transition metal phosphides (TMPs) have attracted considerable attention as an advanced electrocatalyst for hydrogen evolution reaction (HER). Nevertheless, the catalytic efficiency of single-component TMPs is still restricted that cannot endure long-term running and easy to be corroded especially under harsh conditions. In this work, a multicomponent electrocatalyst combined with CoP/Ni₂P heteronanoparticles and Co/Ni single-atom active sites (denoted as N–C@CoP/Ni₂P) is rational designed and prepared. The obtained N–C@CoP/Ni₂P electrode material exhibits enhanced performance with the overpotential of 153 mV at 10 mA cm^?2, and the small Tafel value of 53.01 mV dec^?1 in 0.5 M H₂SO₄, and a satisfied result is obtained in basic media as well. The outstanding HER performance is mainly benefiting from the synergistic effect between CoP and Ni₂P, and the highly catalytic faction of atomic Co/Ni dual sites. Furthermore, a powerful conductive network fabricated by N-doped carbon skeleton and in-situ grown CNTs improves the conductivity of catalyst. Such a stereoscopic 3D nanostructure is also facile to accelerate the shuttle of electrons and ions.     

Remarkable electrocatalytic activity of Ni-nanoparticles on MOF-derived ZrO2-porous carbon/reduced graphene oxide towards methanol oxidation

In the present work, a porous carbonaceous platform containing zirconium oxide was used for spreading Ni nanoparticles, and applied to methanol oxidation. The platform was obtained by calcination of a metal-organic framework (MOF) attached to graphene oxide. Nickel nanoparticles were then deposited on the nanocomposite by chemical reduction from a Ni²⁺ solution. The obtained electrocatalyst was characterized by different methods. An excellent electrocatalytic behavior was observed towards methanol oxidation in alkaline medium (j ~ 240 mA cm^?2 or ~ 626 mA mg^?1 in 1.0 M methanol). The results of methanol oxidation by various electrochemical studies (cyclic voltammetry, electrochemical impedance spectroscopy, chronoamperometry and chronopotentiometry) revealed the effective synergy between reduced graphene oxide, porous carbon material, ZrO₂ metal oxide and Ni nanoparticles. Good durability and stability of the proposed electrocatalyst and significantly increased current density of methanol oxidation suggest it as a potential alternative for Pt-based electrocatalysts in direct methanol fuel cells.     

Tuning of electrocatalytic activity of mixed metal dichalcogenides supported NiMoP coatings for alkaline hydrogen evolution reaction

The mixed metal dichalcogenides combination of WS₂–MoS₂ was coated onto Cu substrate by electroless NiMoP plating technique and the electrocatalytic hydrogen evolution reaction (HER) performance was investigated. The enhanced structural, morphological parameters and boosted electrocatalytic performance of the various metal-metal molar ratio of WS₂–MoS₂ onto NiMoP plate were identified under variable operating conditions and it was successfully evaluated by various characterization techniques. The well-defined crystalline nature, phase, particle size, structure, elemental analysis and surface morphology of prepared coatings were analyzed by FESEM, XRD, AFM and EDS mapping. The electrochemical analysis was performed using open circuit potential (OCP) analysis, chronoamperometry (CA), electrochemical impedance spectroscopy (EIS), Tafel curves, linear sweep voltammetry (LSV), cyclic voltammetry (CV) and polarization studies to find the activity of prepared electrocatalyst towards electrochemical hydrogen evolution reactions. The performance of bare NiMoP and WS₂–MoS₂/NiMoP plates were compared and found that the HER activity of NiMoP can be reinforced by composite incorporation through the synergic effect arises with in the catalytic system, which improves surface roughness and enhances the magnitude of electrocatalyst toward HER. The achievement of enhanced catalytic performance of coatings was authenticate by the kinetic parameters such as decreases in Tafel slope (98 mV dec^?1), enhanced exchange current densities (9.32 × 10^?4 A cm^?2), and a lower overpotential. The consistent performance and durability of the catalyst were also investigated. The enhanced electrocatalytic activity of WS₂–MoS₂/NiMoP coatings increased with respect to the surface-active sites associated with combination of mixed dichalcogenides and the synergic effect arises in between different components present in the coating system. This work envisages the progressive strategies for the economical exploration of a novel WS₂–MoS₂/NiMoP water splitting catalyst used for large scale H₂ generation. The prepared WS₂–MoS₂/NiMoP embedded Cu substrate possess high catalytic activity due to its least overpotential of 101 mV at a benchmark current density of 10 mA cm^?2, which demonstrated the sustainable, efficient and promising electrocatalytic property of prepared catalyst towards HER under alkaline conditions.     

Co2P nanoparticles supported on cobalt-embedded N-doped carbon materials as a bifunctional electrocatalyst for rechargeable Zn-air batteries

Reversible oxygen electrodes with high efficiencies for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are of great significance for a variety of energy conversion devices, such as fuel cells and metal-air batteries. Herein, Co₂P nanoparticles supported on cobalt-embedded N-doped carbon materials (Co₂P/Co–N–C) have been prepared by pyrolysis of cobalt zeolitic imidazolate framework and phosphating post treatment. The optimal Co₂P/Co–N–C composite shows excellent bifunctional electrocatalytic activities for both OER (the potential of 1.65 V at 10 mA cm^?2) and ORR (half-wave potential of 0.82 V). As a practical demonstration, Co₂P/Co–N–C catalyst is used as an air electrode in liquid Zn-air battery, which displays a large open-circuit voltage of 1.50 V, a high peak-power density of 158 mW cm^?2 and excellent reversibility of over 205 h at 5 mA cm^?2. Moreover, the flexible Zn-air battery with Co₂P/Co–N–C exhibits a high open-circuit voltage of 1.46 V and the good flexibility with different angles. This work provides inspiration to explore new strategies for electrochemical energy conversion and storage.     

Co-doped Ni–Fe spinels for electrocatalytic oxidation over glycerol

A series of Co-doped Ni–Fe spinels (NiCo_xFe_(2-x)O₄, x = 0.2, 0.4, 0.6, 0.8, 1.0, 1.4, 1.8, 2) were prepared at optimum calcination temperature (700 °C) by the sol-gel method and then applied for the electrocatalytic oxidation over glycerol. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Tafel curve, and chronoamperometry (i-t) were performed to investigate electrochemical performance of as-prepared spinel catalysts. The results showed that NiCo_0·8Fe_1·2O₄ exhibited distinct redox peaks and the larger CV area (626.2 ± 0.03 μV A cm^?2), lower Rct (42.42 ± 0.03 Ω) and Tafel slope (21 mV dec^?1) than that of pristine NiFe₂O₄ and NiCo₂O₄, signifying Co-doped NiFe₂O₄ is beneficial to accelerate the catalytic oxidation of glycerol. Moreover, the ECSA and stability of NiCo_0·8Fe_1·2O₄ were also observably improved. This excellent performance is comparable to that of commercial Pt/C (20 wt.%)-SA. The enhanced electrocatalytic property of NiCo_0·8Fe_1·2O₄ is ascribed to the uneven distribution of oxygen in NiFe₂O₄ structure caused by Co doping, thus forming oxygen defect sites.     

Facile one-step fabrication of bimetallic Co–Ni–P hollow nanospheres anchored on reduced graphene oxide as highly efficient electrocatalyst for hydrogen evolution reaction

It is significant but challenging to develop noble-metal-free electrocatalysts exhibiting high activity and long-term stability toward hydrogen evolution reaction (HER) to satisfy the ever-increasing demand for clean and renewable energy. Herein, an environment-friendly and low-temperature electroless deposition method is developed for the synthesis of Co–Ni–P hollow nanospheres anchored on reduced graphene oxide nanosheets (Co–Ni–P/RGO). By optimizing the molar ratio of Ni/Co precursor, composition dependent electrocatalytic performances toward HER of nanostructured Co–Ni–P/RGO electrocatalyst are investigated in 1.0 M KOH solution. The results suggest that when the molar ratio of Ni/Co precursor is 3/7, as-prepared ternary Co–Ni–P/RGO electrocatalyst exhibits a remarkably enhanced HER activity in comparison to binary Ni–P/RGO and Co–P/RGO electrocatalysts, delivering a current density of 10 mA cm⁻² at the overpotential of only 207 mV. The value of Tafel slope for nanostructured Co–Ni–P/RGO electrocatalyst reveals that HER process undergoes Volmer-Heyrovsky mechanism. Besides, nanostructured Co–Ni–P/RGO electrocatalyst features superior stability under alkaline condition. The results suggest that nanostructured composite of Co–Ni–P hollow nanospheres/RGO is a potential candidate for hydrogen production through water splitting.     

Ni–Cr alloys for effectively enhancing hydrogen evolution processes in phosphate-buffered neutral electrolytes

Significant efforts have been made to develop highly active non-noble metal-based, affordable metallic and stable electro-catalysts for hydrogen evolution reaction (HER). Strong acid and bases are now used in HER operations to achieve large-scale, sustained H₂ fuel production. However, few studies have utilized phosphate-buffered neutral electrolytes (PBS) in the field of neutral electrolyte technology. In this work, a certain alloys with a Ni–Cr basis have been produced as favorable components for the HER under neutral conditions. Additionally, the current investigations are emphasizing on the concentration of buffer phosphate species in the HER activity of various materials. By employing polarization and electrochemical impedance spectroscopy (EIS) in neutral solutions, the electro-catalytic activity of new alloys on HER was evaluated. According to the preliminary findings, the examined Ni–Cr-based alloys show superior HER catalytic activity in neutral electrolytes. Additionally, the Ni–Cr alloy matrix with Fe and Mo added enhances HER electrocatalytic efficiency while lowering interfacial charge transfer resistance. Due to its low overpotential of ?297 mV @ 10 mA cm^?2 and Tafel slope of 94 mV dec^?1 in 1.0 M PBS media, the Ni–Cr–Mo–Fe alloy exhibits an efficient HER, suggesting that the Ni–Cr–Mo–Fe electrode will be a potential noble metal-free electro-catalyst for HER. The Ni–Cr–Mo–Fe cathode is a readily available and affordable material for the production of HER in neutral medium.     

Solvothermal synthesis of Pd10–Ni45–Co45/rGO composites as novel electrocatalysts for enhancement of the performance of DBFC

In this research, three Pd decorated Ni and Co catalyst nanoparticle were synthesized on reduced graphene oxide (rGO) supports are synthesized through a facile solvothermal procedure. Borohydride oxidation reaction (BOR) activity and performance of prepared electrocatalysts respect to NaBH₄ oxidation is evaluated by various electrochemical techniques in the three-electrode and the fuel cell configuration. Among the prepared catalysts, Pd₁₀–Ni₄₅–Co₄₅/rGO exhibits the highest BOR activity. The cyclic voltammograms showed that the measured current at 0.5 V for the electrode of Pd₁₀–Ni₄₅–Co₄₅/rGO is as much as 108 mA cm⁻² higher than Pd₁₀–Ni₉₀/rGO and 185 mA cm⁻² higher than Pd₁₀Co₉₀/rGO. X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectra were employed to study the morphology and crystal structure of the prepared catalyst. The results of DBFC test show that the Pd₁₀–Ni₄₅–Co₄₅/rGO nanoparticles as anodic catalyst, enhanced power density to 50.4 mW cm⁻² which is 10.5% and 45.2% higher than power density of DBFCs with Pd₁₀–Ni₉₀/rGO (45.6 mW cm⁻²) and Pd₁₀Co₉₀/rGO (34.7 mW cm⁻²) anode catalysts, respectively. These results indicate that the competency of operating procedure for assembling nickel alloys electrodes can improve the activity of the prepared catalysts for BOR considerably.     

A novel co-electrodeposited Co/MoSe2/reduced graphene oxide nanocomposite as electrocatalyst for hydrogen evolution

In this study, a simple and fast electrochemical method was employed to synthesis molybdenum diselenide thin film. The morphology, structure and chemical composition of the nanocomposites were investigated by field emission scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The progressive effects of transition metal ions including Ni, Cu, and Co were surveyed on the hydrogen evolution activity of MoSe₂ thin films. Co/MoSe₂ nanocomposite thin films has significant electrocatalytic activity as compared to other samples, In order to achieve higher performance, preparing Co/MoSe₂/RGO nanocomposite thin film, two strategies including layer by layer electrodeposition and co-electrodeposition has been employed. The presence of reduced graphene oxide leading to the onset potential shifts to more positive values and increase the current density. Also, results showed that the Co/MoSe₂/RGO nanocomposite prepared by co-electrodeposition exhibits the best electrochemical hydrogen evolution at onset potential of −0.18 with an overpotential of −0.45 V.     

New ternary mixed oxides of Fe, Ni and Mo for enhanced oxygen evolution

Ternary mixed oxides of Fe, Ni and Mo with molecular formulas Fe_xNi_1−xMoO₄ (x = 0.25, 0.50 and 0.75) have been prepared by a co-precipitation method and investigated for their structural and electrocatalytic properties by XRD, AFM, electrochemical impedance spectroscopy and anodic Tafel polarization. Results indicate that the apparent oxygen evolution activity of the base (NiMoO₄) electrode significantly increases with introduction of Fe from 0.25 to 0.75 mol. The Tafel slope for the oxygen evolution reaction at low overpotentials is found to be only ∼35 mV on Fe-substituted oxides, while it was ∼75 mV on the base oxide. The reaction follows the first order kinetics with respect to OH⁻ concentration, regardless of Fe content in the oxide.