The usage of active electrocatalysts is a useful approach to accelerate the kinetics of electrochemical reactions and to enhance the efficiency of water splitting. To fabricate active ...electrocatalysts, the creation of new structures that can be easily constructed has always been a research interest. Ni–Fe based alloys are generally known as active OER catalyst. However, in this study, a novel Ni–Fe micro/nano urchin-like structure is reported to be active for both HER and OER. This is the first report of the fabrication of this morphology by a fast, one-step, and affordable electrodeposition method as an efficient HER/OER electrocatalyst. The optimized Ni–Fe coating on Cu substrate demonstrated promising HER activity with low overpotentials of −124 and −243 mV at the current densities of −10 and −100 mA cm−2, respectively. Moreover, the fabricated Ni–Fe urchin-like catalyst is highly active toward OER, requiring overpotentials of only 292 and 374 mV to deliver 10 and 100 mA cm−2. The unique structure of the synthesized coating with an abundant number of micro/nano-scale cones is suggested to play a vital role in the superior HER/OER activity of the catalyst. This article introduces a cost-effective method for the fabrication of a novel urchin-like Ni–Fe alloy as a highly active bifunctional water splitting electrocatalyst.
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•Ni–Fe-urchin-like structure was developed using electrodeposition.•Ni–Fe nanostructure showed outstanding electrocatalytic activity.•Synergistic effect and high surface area were the factors contributed in this excellent activity.•Fabricated nanostructure exhibited favorable catalytic stability.
In this study, the manufacture of Ni-W-Mo-Co-P, Ni-Mo-Co-P, Ni-W-Co-P, Ni-W-Mo -P, Ni-Co-P, Ni-Mo-P, Ni-W-P, and Ni-P alloying coatings through electroless method on the copper substrate was ...investigated. The elemental and structural tests showed that the alteration of the Ni-P electroless basic bath composition by introducing sodium tungstate, sodium molybdate, and cobalt chloride additives enabled the deposition of alloying coatings. Linear Sweep Voltametry (LSV) tests revealed that the Ni-W-Mo-Co-P sample (NWMCP) coated in an alkaline bath with 18 g/l Nickel (II) sulfate, 12 g/l Ammonium acetate, 12 g/l Sodium citrate, 12 ml Lactic acid, 12 g/l Sodium hypophosphite, 8 g/l Sodium tungstate, 0.2 g/l Sodium molybdate, and 10 g/l Cobalt (II) chloride was featured with the best electrocatalytic properties with η10 = −41, η20 = −46, η100 = −67 mV and tafel slope of 38 mV.dec−1. Scanning Electron Microscope (SEM) observations and Cyclic Voltametry (CV) electrochemical tests showed that morphology had a negligible effect on electrocatalytic performance of the coating. In addition, the presence of alloying elements improved the coating intrinsic properties by changing its electronic structure. Electrocatalytic stability was assessed using chronoamperometry, cyclic voltammetry, and stepwise chronoamperometry tests, introducing NWMCP sample a durable electrode generation with good stability.
The synthesis of electrocatalysts which used simultaneously as electrodes for the hydrazine oxidation reaction (HzOR), and hydrogen evolution reaction (HER) can significantly improve the efficiency ...of hydrogen production in the water splitting process. Here, Ni–Co–Fe–P binder-free nanosheets were fabricated using the electrochemical deposition method and used as an effective, stable, and cost-effective electrode for hydrazine-assisted electrochemical hydrogen production. Taking advantage of high surface area, being binder-free, and synergistic effect between the elements in the electrode composition, this electrode showed unique electrocatalytic activity and stability. When this electrode was used as a bifunctional electrode for HzOR-HER, a cell voltage of 94 mV was required to reach a current density of 10 mA cm−2. The results of this study indicated that the Ni–Co–Fe–P electrode is an excellent candidate for the hydrogen production industry.
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•Binder-free Ni–Co–Fe–P nanosheets was electrodeposited by two-step method.•Fabricated electrode demonstrated fantastic performance for HER and HzOR.•DFT calculation demonstrated the synergistic effect between elements.•Favourable stability was obtained for hydrazine assisted hydrogen generation.
Water electrolysis is known as an efficient strategy in the direction of green energy production to remove fossil fuels and generate hydrogen. On the other hand, the slow kinetics of the anodic ...half-reaction (OER) significantly reduces the efficiency of this system. Therefore, choosing an alternative to OER has become a new and reliable approach. Urea oxidation reaction (UOR) is considered an excellent alternative to OER due to its low required potential (0.37V), the abundance of urea sources (industrial waste and human/animal urine), and harmless by-products (N2, CO2). Electrocatalysts based on non-noble metals such as nickel, cobalt, molybdenum, manganese, iron, and copper in electrochemical urea-assisted water splitting due to their high electrocatalytic performance and lower price than noble metals play an essential role in reducing costs and increasing the efficiency of this system. This review investigated the electrochemical water splitting reaction and its anodic and cathodic half-reactions. Then, urea, electro-oxidation of urea, methods of making catalysts, measuring parameters of electrocatalytic properties, solutions to improve performance, and types of non-noble catalysts used in this field were reviewed, and finally, challenges and solutions to improve results in the future were introduced.
•Hydrogen production efficiency can be enhanced assisted by urea oxidation reaction.•Different HER, OER and UOR mechanisms have been addressed in this article.•Recent advances in catalysts for UOR assisted hydrogen production was reviewed.
In the present work, high-temperature cyclic oxidation of ferritic stainless steel (FSS) with minor addition of Nb and Ti elements has been carried out at 800 °C in air for 70 cycles. Thermal cycling ...consists of 1 h heating in furnace followed by 15 min cooling to room temperature outside the furnace. The weights of all the specimens were measured every 1 cycle. The specimens were examined by scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS). The purpose of making this alloy was for application in solid oxide fuel cells (SOFCs) interconnects. The addition of minor alloying elements, especially Nb, led to formation of Laves phases in oxide/metal interface and prevented the diffusion of cation to the oxide scale. It is also a barrier for the influence of the oxygen anion to the inward of the FSS. The presence of high amount of Nb and low amount of Ti were effective on improving of the oxidation. By increasing amount of Ti compare to Nb in this steel caused the increased oxidation rate.
•Presence of Nb formed Laves-phase in the oxide/metal interface.•Inward diffusion of oxygen was reduced by Nb and Ti addition.•Nb and Ti addition were effective to enhance the oxidation resistance.
Finding cost-effective electrocatalysts that can match the performance of noble metals like platinum is crucial for renewable hydrogen energy generation. In this study, the electrocatalytic ...properties of a nickel sulfide compound deposited on a porous copper network that is formed on a nickel foam substrate are investigated. To achieve this goal, the dynamic hydrogen bubble template method was employed. Copper and nickel sulfide electrodeposited in 5 s at 6 A cm−2. The presence of the copper layer resulted in a potential requirement of 98 mV, to achieve current densities of 10 mA cm−2, compared to 120 mV, when the porous copper substrate was not present. The ECSA was found to be significantly increased by the presence of the copper layer, as determined by examining the CV test and calculating the electrochemically active surface area. Ni3S2@Cu@NF is an excellent choice for electrocatalyst when it comes to HER in alkaline media.
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•DHBT were used to electrodeposit coatings of Cu and Ni3S2.•Presence of Cu layer increased electrocatalytic properties of Ni3S2@Cu@NF.•According to EIS, Ni3S2@Cu@NF had the best electrocatalytic properties with low Rct.
The development of highly effective and economical catalysts for hydrogen production from the electrochemical water splitting is considered as a promising strategy for the hydrogen production ...industrialization. Among the various compounds, transition-metal-phosphide electrodes have powerful performance and efficiency, which in the recent years have shown great potential to replace noble electrodes. Among the synthesis methods of phosphide-based electrodes, the electrodeposition technique has recently attracted special attention among researchers, and remarkable progress has been made in this research field. Due to the importance of this topic and the lack of a suitable review article, here, recent developments in the field of electrodeposition of phosphide-based nanostructure for hydrogen production are summarized. In this review article, the performance of synthesized electrodes by different applied current and potential programs is discussed, and concluding remarks and future trend are presented.
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•Ni-Co-P/rGO flower-like nanostructure via Chronoamperometry method has been synthesized.•RGO nanosheets enhanced electrodes electron conductivity and catalytic ...activity.•Ni-Co-P-20/rGO shows the best performance with η10 equal to 0.53 mV and 1.23 V toward HER and UOR.•Maximum decrease in η100 was exhibited 0.303 V by Ni0.43 Co0.47 P0.01/rGO as an anode catalyst in two-electrode cell.
Replacing the inert oxygen evolution reaction (OER) with alternative electrochemical reactions is critical for large-scale hydrogen generation. Here the Ni-Co-P flower-like nanostructure coated on reduced graphene oxide which was synthesized via two-step electrodeposition method (as Ni-Co-P/rGO/NF) is described. First, rGO was deposited on the nickel foam precursor by the pulse-reverse electrodeposition, then Ni-Co-P nano-layer by the Chronoamperometry was electrodeposited. The η10 for HER and UOR was 53 mV and 1.23 V, respectively, demonstrate enhanced electrocatalytic activity. XRD, XPS, and TEM analysis revealed that the Ni-Co-P/rGO catalyst has a flower-like structure depending on its composition. In the two-electrode cell at a voltage of 1.35 V, the generated current density of urea electrolysis (37.84 mA cm−2 in 0.33 M urea + 1.0 M KOH electrolyte) was 3.31 times greater than that of the conventional water splitting (11.41 mA cm−2). According to the findings, Ni-Co-P/rGO could be employed as a dual-functional catalyst toward UOR and HER for energy-saving and H2 generation.
In this paper, NiFeS@CoFeLDH nanostructure was synthesized for the first time by electrochemical method in two steps. In the first stage, the first layer of NiFeS was deposited on the nickel foam ...(NF) substrate, and in the second stage, the second layer of cobalt-iron layered double hydroxide (CoFeLDH)by controlling the electrodeposition condition was deposited on the first. The deposition time and potential were optimized. The optimized NiFeS@CoFeLDH coating on NF has promising hydrogen evolution reaction (HER) activity, which exhibits small overpotentials of − 191.5, and − 304.0, at the current densities of − 10, and − 100 mA. cm−2, respectively. Furthermore, the synthesized NiFeS@CoFeLDH electrocatalyst only needs 358 mV overpotentials to operate at a current density of 10 mA. cm−2 indicating its great performance for the urea oxidation reaction (UOR). The electrode stability was examined at an industrial scale current density of − 100 and 10 mA. cm−2 for HER and UOR respectively, which showed a very stable response for at least 10 h. The results showed that the simultaneous application of NiFeS and CoFeLDH electrocatalysts has a synergistic effect that increases the surface-to-volume ratio and improves the active sites. According to high performance for HER and UOR and also simple, fast, and binder-free synthesis without using expensive materials for preparing the electrocatalyst layer, the proposed electrode can be used as a good candidate for water splitting in the presence of urea.
•Two electrocatalysts including CoFeLDH and NiFeS have been used simultaneously.•This composition has a synergic effect and better performance for HER and UOR.•The electrochemical synthesis is done in a short time and at ambient temperature.•The overvoltage of HER at − 10 mA. cm−2 was − 191 mV and for UOR was + 358 mV.
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•Binder-free P-doped Ni-Se electrodes were fabricated via two-step method.•P-doped Ni-Se electrode demonstrated fantastic performance in wide pH range.•DFT calculation showed the ...synergistic effect for improving the activity.•Favorable stability in wide pH range was obtained for hydrogen generation.
Transition metal selenide materials are extensively investigated as electrocatalysts for the hydrogen evolution reaction (HER). Despite having good electrical transportability, they suffer from low abundance catalytic active sites and relatively poor long-term stability. Herein, we demonstrate phosphorous doping in NiSe as an effective strategy to simultaneously boost electrocatalytic activity and stability. The phosphorous doped NiSe catalyst needs the lowest overpotentials of 90, 101, 212, and 296 mV at 10 mAcm−2 in alkaline, acidic, neutral, and seawater electrolytes, respectively, as well as continuous stable operation over 100 h. The high exchange current density of 1.379 mAcm−2, the excellent mass activity of 23.95 Ag−1, and a turnover frequency (TOF) value of 0.339 s−1 at 150 mV indicate the promising electrocatalytic HER performance of the P-doped NiSe catalyst. Our experimental data and theoretical calculations confirm that the advantage of HER activity and stability of P-doped NiSe originates from enriched catalytic active sites with near-zero H adsorption free energy and tuned electronic structure. This work provides a blueprint for the design and synthesis of best-in-class selenide-based HER catalysts.
