Abstract
In this work, a dealloying technique is proposed as a synthesis method to obtain highly porous Nickel electrodes starting from Ni-Cu co-deposit: pulsed corrosion is applied adopting different corrosion and relaxation times. Different morphologies, pore size distribution and residual copper amount were obtained depending on the corrosion conditions. For the developed electrodes, the surface roughness factor, Rf, was evaluated by electrochemical impedance spectroscopy (EIS). The hydrogen evolution reaction (HER) on these electrodes was evaluated by means of steady-state polarization curves, and the related parameters were derived by Tafel analysis. Finally, a thin layer of NiO on the porous structures was obtained to exploit the semiconductor characteristic of the oxide, so that an extra-photopotential was obtained by the simulated solar light action. Results demonstrate greater apparent activity of the developed electrodes towards HER in comparison with commercial smooth Ni electrode, which can be mainly attributed to the large Rf obtained with the proposed technique.
Highlights
The production of hydrogen by electrocatalytic or photoelectrocatalytic (PEC) water splitting driven by renewable energy, and its subsequent use in a fuel cell, could represent a zero-emission process in which the storage of H2 could mitigate the spatial and temporal discontinuities of renewable energy resources [1,2]
Many earth-abundant hydrogen evolution reaction (HER) catalysts such as transition metal chalcogenides [4,5] or carbides [6,7] have exhibited high activities in acid solutions approaching that of Pt, all of them cannot operate satisfactorily in alkaline electrolytes [8]
The Tafel analysis revealed that the exchange current density calculated with respect to the real surface area, was higher in sample S1–5 rather than sample
Summary
The production of hydrogen by electrocatalytic or photoelectrocatalytic (PEC) water splitting driven by renewable energy, and its subsequent use in a fuel cell, could represent a zero-emission process in which the storage of H2 could mitigate the spatial and temporal discontinuities of renewable energy resources [1,2]. Due to the high overpotential losses involved in the gas evolution reactions occurring at the electrodes, the electrolytic H2 production is still not competitive, at large scale, with the traditional process of H2 production from fossil fuels [3]. Many earth-abundant HER catalysts such as transition metal chalcogenides [4,5] or carbides [6,7] have exhibited high activities in acid solutions approaching that of Pt, all of them cannot operate satisfactorily in alkaline electrolytes [8]. Nickel-based electrocatalysts, either as monofunctional or bifunctional materials, were proposed as an economical and efficient replacement to these expensive metal precursors, that exhibited very promising electrocatalytic activity and stability toward oxygen and hydrogen evolution reactions [9,10,11,12]
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