Niobium-based semiconductor electrodes for hydrogen evolution reaction

This contribution focusses on the use of Nb-based materials for the preparation of hybrid nickel-semiconductor electrodes for use in the electrochemical generation of hydrogen. The Nb-based semiconductors (i.e., Nb2O5 and Nb-3(PO4)(5) show good performance for the H-2 evolution reaction (HER) using a non-toxic electrolyte (K2CO3) under true water-splitting conditions. Particularly, Nb2O5 shows HER efficiency two orders of magnitude higher than its TiO2 counterparts. Tafel analysis suggests the HER mechanism is the same for all type of electrodes studied and electrochemical impedance spectroscopy indicates these hybrid Ni Nb-semiconductor electrodes are sensitive to light exposure, unlike TiO2. We propose that the differences in impedance upon irradiation are due to the band structure of these hybrid electrodes, which have lower Schottky barrier heights and show smaller work function values. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.