Phosphating CoMoO₄-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-Fe₂O₃ (Zr:Fe₂O₃) and phosphating cobalt molybdate electrocatalyst (P-CoMoO₄) to ameliorate the above difficulties. The conductivity and carrier density of hematite significantly increase by Zr doping. Synergistically, the incorporation of P-CoMoO₄ constructs type II heterojunction with α-Fe₂O₃, realizing the photogenerated electron-hole directional separation. What is more, phosphating treated CoMoO₄ loading creates an intermediate surface state on the photoanode, which plays an indispensable role in trapping and transport of photogenerated holes. Meanwhile, P-CoMoO₄ as the cocatalyst not only offers rich active site of Co²⁺ but also reduces the barrier and expedites the kinetics for the water oxidation reaction. As a consequence, the resulting P-CoMoO₄/Zr:Fe₂O₃ composite photoanode exhibits an impressive photocurrent density of 2.27 mA cm^-2 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.