The influence of Ir content in (Ni0.4Co0.6)1-xIrx-oxide anodes on their electrocatalytic activity in oxygen evolution by acidic and alkaline water electrolysis

Abstract

Hydrogen is envisaged as the future energy fuel vector. Unfortunately, one of the most environmentally-viable hydrogen production option, water electrolysis (when coupled with solar/wind/hydro electrical energy) is still not energy efficient, as it requires expensive electrocatalytically-active noble metal anodes. The authors recently identified Ni0.4Co0.6-oxide as good alternative anode-material candidate, nevertheless, the electrocatalytic activity of this anode needs further augmentation. Therefore, with the aim of improving the anode's activity towards oxygen evolution in both the acidic and alkaline media, the influence of addition of small amounts (≤10%) of Ir to Ni0.4Co0.6-oxide was studied. The investigation showed that the incorporation of Ir into the Ni0.4Co0.6-oxide matrix yielded a synergetic effect, resulting in a significant improvement of the anode's intrinsic electrocatalytic activity relative to both Ni0.4Co0.6-oxide and pure Ir-oxide. This was ascribed to the change in the electronic structure of the catalyst and to the reduction in band gap energy relative to Ni0.4Co0.6-oxide and Ir-oxide. The as-made (Ni0.4Co0.6)0.9Ir0.10-oxide composition was found to be stable and significantly more active than the current state-of-the-art IrO2 PEM oxygen-evolution anode, while also offering a considerably higher electrocatalytic activity than nickel anodes used in alkaline electrolysers.