Constructing the Fe/Cr double (oxy)hydroxides on Fe3O4 for boosting the electrochemical oxygen evolution in alkaline seawater and domestic sewage

Developing the electrocatalysts which can be directly performed in sewage and seawater without further treatment kills two birds with one stone since it can turn waste into raw materials and produce H2. Herein, the heterointerface between Fe(Cr)OOH and Fe3O4 is constructed through a scalable method. Systematic experiments and theoretical calculations confirmed that the Fe(Cr)OOH coupling with Fe3O4 can significantly decrease the oxygen evolution reaction (OER) overpotential (η500 = 241 mV in 1 M KOH) and promote the mass and electron transfer. Impressively, this electrode could work efficiently and maintain 100 mA cm−2 for 100 h in both alkaline seawater and domestic sewage. The electrolyzer using such electrode as anode could deliver a current density of 500 mA cm−2 in 5 M KOH at a small cell voltage of 1.62 V. This work provides a facile route to prepare efficient and low-cost OER catalysts, which has important implications for energy conversion.