Efficient solar fuel production enabled by an iodide oxidation reaction on atomic layer deposited MoS₂

Abstract Oxygen evolution reaction (OER) as a half‐anodic reaction of water splitting hinders the overall reaction efficiency owing to its thermodynamic and kinetic limitations. Iodide oxidation reaction (IOR) with low thermodynamic barrier and rapid reaction kinetics is a promising alternative to the OER. Herein, we present a molybdenum disulfide (MoS₂) electrocatalyst for a high‐efficiency and remarkably durable anode enabling IOR. MoS₂ nanosheets deposited on a porous carbon paper via atomic layer deposition show an IOR current density of 10 mA cm^–2 at an anodic potential of 0.63 V with respect to the reversible hydrogen electrode owing to the porous substrate as well as the intrinsic iodide oxidation capability of MoS₂ as confirmed by theoretical calculations. The lower positive potential applied to the MoS₂‐based heterostructure during IOR electrocatalysis prevents deterioration of the active sites on MoS₂, resulting in exceptional durability of 200 h. Subsequently, we fabricate a two‐electrode system comprising a MoS₂ anode for IOR combined with a commercial Pt@C catalyst cathode for hydrogen evolution reaction. Moreover, the photovoltaic–electrochemical hydrogen production device comprising this electrolyzer and a single perovskite photovoltaic cell shows a record‐high current density of 21 mA cm^–2 at 1 sun under unbiased conditions.