The Aurivillius compound CoBi2O2F4 – an efficient catalyst for electrolytic water oxidation after liquid exfoliation

Investigation of new high-efficiency catalysts for the oxygen evolution reaction (OER) is important for propelling the practical applications of water splitting. Here we report the Aurivillius compound CoBi2O2F4 to be a novel catalyst for catalytic OER. After liquid exfoliation of CoBi2O2F4 crystals in isopropanol, the resulting thin sheets deliver a low overpotential of 334 mV and a small Tafel slope of 47 mV dec(-1) for catalytic OER, exhibiting substantially higher activity and faster kinetics compared with as-synthesized crystals. This attributes to the increase in accessible surface area and dangling bonds on the edges providing more active sites exposed on the surface after exfoliation. The positive effects of F- anions to benefit OH- adsorption/combination and p-block Bi3+ cations to direct reactants to preferred sites are proposed to synergistically improve the Co-active centers for catalysis; based on this, the OER reaction mechanism on this new catalyst is discussed.