Self-supported FeCoNi(OHy)Ox oxy-hydroxide doped with Cr and Cu as robust low-loading catalyst for the alkaline oxygen evolution reaction

Self-supported FeCoNi(OHy)Ox oxy-hydroxides co-doped with Cr and Cu were obtained from a CrFeCoNiCu low ordered high entropy precursor synthesised by electrodeposition onto carbon cloth fibres (act-CrFeCoNiCu/CC). For comparison a dopant-free FeCoNi(OHy)Ox catalyst (act-FeCoNi/CC) was also synthesised following the same route. No heat treatment was performed to retain their low ordered structure. When assessed towards the oxygen evolution reaction (OER) in alkaline electrolyte, act-CrFeCoNiCu/CC and act-FeCoNi/CC catalyst reached a comparable current density of 10 mA cm−2 at ca. 1.6 VRHE (η10 of 380–390 mV). Nevertheless, Cr and Cu co-doping translated into improved stability. Evident degradation was observed during OER for act-FeCoNi/CC after 12 h operating at 100 mA cm−2, whereas no signs of degradation were detected for act-CrFeCoNiCu/CC under the same reaction conditions. The latter catalyst even delivered a constant potential for 160 h at 50 mA cm−2 aided to the stabilizing effect of Cr and Cu co-doping.