Electrodeposition and hydrogen evolution performance of Ir-Ni thin film electrocatalysts
Iridium nickel(Ir-Ni)thin films were prepared on copper foam substrates by electrodeposition technology.The electrocatalytic hydrogen evolution(HER)performance of the films was expected to be improved by depending on the three-dimensional porous structure of foam copper(CF)and the excellent catalytic and corrosion resistance of Ir-Ni thin films.The electrodeposition process was executed under galvanostatic method.The resulting Ir-Ni thin film was subsequently compared with pure Ir and Ni films,which were also electrodeposited on copper foam.The surface morphology and chemical composition of the films were analyzed employing scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and X-ray photoelectron spectroscopy(XPS),and the electrocatalytic performance of the films was evaluated via linear sweep voltammetry(LSV).The results showed that the Ir-Ni thin film was successfully adhered to the porous and hollow-structured copper foam,exhibiting a relatively rougher surface compared to the pure Ni film.The film was predominantly composed of metallic Ir,with an atomic content of 80.0±1.2,further demonstrating the success of the deposition process.Remarkably,the Ir-Ni/CF demonstrated superior HER performance,achieving a current density of 10 mA·cm-2 with an overpotential of merely 60 mV and a Tafel slope as low as 40 mV·dec-1.The exchange current density jo of Ir-Ni/CF,calculated by the Tafel extrapolation method,was 0.657 mA·cm-2,approximately twice that of the Ni film and 87.6％of the commercially available Pt/C catalysts.Furthermore,it exhibited commendable electrocatalytic stability in an alkaline solution,as evidenced by prolonged hydrogen evolution experiments.The electrocatalytic activity of the Ir-Ni/CF was significantly higher than that of Ir/CF and Ni/CF.This improvement can be primarily attributed to two pivotal factors:the increase in active surface area due to the relative roughness of the film,and the cooperative effect of Ir and Ni in the HER process.
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