High-Performance Electrochemical and Photoelectrochemical Water Splitting at Neutral pH by Ir Nanocluster-Anchored CoFe-Layered Double Hydroxide Nanosheets

Abstract

Highly efficient electrocatalysts for the oxygen evolutionreaction(OER) in neutral electrolytes are indispensable for practical electrochemicaland photoelectrochemical water splitting technologies. However, thereis a lack of good, neutral OER electrocatalysts because of the poorstability when H+ accumulates during the OER and slow OERkinetics at neutral pH. Herein, we report Ir species nanocluster-anchored,Co/Fe-layered double hydroxide (LDH) nanostructures in which the crystallinenature of LDH-restrained corrosion associated with H+ andthe Ir species dramatically enhanced the OEC kinetics at neutral pH.The optimized OER electrocatalyst demonstrated a low overpotentialof 323 mV (at 10 mA cm(-2)) and a record low Tafelslope of 42.8 mV dec(-1). When it was integrated withan organic semiconductor-based photoanode, we obtained a photocurrentdensity of 15.2 mA cm(-2) at 1.23 V versus reversiblehydrogen in neutral electrolyte, which is the highest among all reportedphotoanodes to our knowledge.