From Doped Coordination Polymer Precursor to Cobalt-Doped ZnO Electrocatalyst for Alkaline Hydrogen Evolution Reaction

Abstract

The large-scale application of water electrolysis, for clean H2 production, requires the development of eco-friendly and low-cost electrocatalysts with high activity for hydrogen evolution reaction (HER) in alkaline media. The excellent alternatives to the benchmark noble metal-based HER electrocatalyst are transition metal oxides (TMO). Because of the nontoxicity, cost-effectiveness, availability, and easy electronic structure tuning, zinc oxide (ZnO) is a good TMO candidate. However, ZnO shows poor performance for HER electrocatalysis and therefore has been much less reported. Herein, it is reported that ZnO can be developed as a good HER electrocatalyst in alkaline media through simultaneously proper cobalt loading at the precursor level (coordination polymer) and defects engineering. The optimum amount of cobalt in ZnO shows an overpotential of 385 mV at 10 mA cm-2 (lower than that of ZnO and Co3O4) and a small Tafel slope of 76 mV dec-1. The introduction of cobalt at the precursor level and subsequently in the wurtzite frame of ZnO as revealed by the analyses, allows to considerably lower the bandgap and increasing the number of defects in the structure, thereby boosting the electrocatalytic performance. This work highlights the potential of cheap and environmentally friendly TMO as alternative HER electrocatalysts for large-scale alkaline water electrolysis.