Phosphating CoMoO-Modified Hematite-Based Photoanode Enhances Surface Charge Transfer and Reaction Activity for Efficient Photoelectrochemical Water Oxidation.

The photoelectrochemical properties of hematite-based photoanodes are hindered by severe carrier recombination and poor reaction activity, which is a major challenge. Herein, we coupled zirconium-doped α-FeO (Zr:FeO) and phosphating cobalt molybdate electrocatalyst (P-CoMoO) to ameliorate the above difficulties. The conductivity and carrier density of hematite significantly increase by Zr doping. Synergistically, the incorporation of P-CoMoO constructs type II heterojunction with α-FeO, realizing the photogenerated electron-hole directional separation. What is more, phosphating treated CoMoO loading creates an intermediate surface state on the photoanode, which plays an indispensable role in trapping and transport of photogenerated holes. Meanwhile, P-CoMoO as the cocatalyst not only offers rich active site of Co but also reduces the barrier and expedites the kinetics for the water oxidation reaction. As a consequence, the resulting P-CoMoO/Zr:FeO composite photoanode exhibits an impressive photocurrent density of 2.27 mA cm at 1.23 V vs RHE and onset potential as low as 0.68 V vs RHE. This work presents a simple yet feasible strategy of collaborative modification and surface reconstruction to achieve efficient charge separation and transfer of photoanode materials.