High valence chromium regulated cobalt-iron-hydroxide for enhanced water oxidation

In this report, a Cr regulated ternary CoFeCr hydroxide microsphere composite for enhanced water oxidation was fabricated using a facile electrodeposition method. The incorporation of Cr affects the oxidation state of Co and compared to the binary cobalt-iron hydroxide composite, the ternary composite shows excellent electrocatalytic performance for oxygen evolution reaction (OER) in alkaline media, whose onset potential is only around 1.43 V vs reversible hydrogen electrode (RHE) and the overpotential is merely of 270 mV to achieve a current density of 100 mA cm(-2) in 1 M KOH. This enhanced oxygen evolution activity is attributed to the regulation effect of chromium. In other words, during water oxidation, chromium in the composite is partially oxidized into high valence 6 + and the electrons generated by this oxidation reaction can be transferred to the cobalt cites to maintain cobalt at a relatively lower oxidation valence state (but OER active), which accelerates the third electron-transfer process (M-O + OH- -> M-OOH + e(-)).