**Porous Ni Photocathodes Obtained by Selective Corrosion of Ni-Cu Films: Synthesis and Photoelectrochemical Characterization**

**Laura Mais 1, Simonetta Palmas 1, Michele Mascia 1, Elisa Sechi 1, Maria Francesca Casula 1, Jesus Rodriguez <sup>2</sup> and Annalisa Vacca 1,\***


Received: 5 April 2019; Accepted: 13 May 2019; Published: 16 May 2019

**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.

**Keywords:** porous nickel; selective corrosion; hydrogen evolution reaction; photoelectrocatalysis
