In situ Hydrothermal Oxidation of Ternary FeCoNi Alloy Electrode for Overall Water Splitting

Abstract

Exploring noble metal-free catalyst materials for high efficient electrochemical water splitting to produce hydrogen is strongly desired for renewable energy development. In this article, a novel bifunctional catalytic electrode of insitu-grown type for alkaline water splitting based on FeCoNi alloy substrate has been successfully prepared via a facile one-step hydrothermal oxidation route in an alkaline hydrogen peroxide medium. It shows that the matrix alloy with the atom ratio 4:3:3 of Fe:Co:Ni can obtain the best catalytic performance when hydrothermally treated at 180°C for 18 h in the solution containing 1.8 M hydrogen peroxide and 3.6 M sodium hydroxide. The as-prepared Fe0.4Co0.3Ni0.3-1.8 electrode exhibits small overpotentials of only 184 and 175 mV at electrolysis current density of 10 mA cm−2 for alkaline OER and HER processes, respectively. The overall water splitting at electrolysis current density of 10 mA cm−2 can be stably delivered at a low cell voltage of 1.62 V. These characteristics including the large specific surface area, the high surface nickel content, the abundant catalyst species, the balanced distribution between bivalent and trivalent metal ions, and the strong binding of in-situ naturally growed catalytic layer to matrix are responsible for the prominent catalytic performance of the Fe0.4Co0.3Ni0.3-1.8 electrode, which can act as a possible replacement for expensive noble metal-based materials.