Enhanced Charge Transfer via Heterogeneous Doping Promotes Hematite Photoelectrodes for Efficient Solar H₂O₂ Synthesis

Photoelectrochemical (PEC) water splitting into hydrogen peroxide (H2O2) and hydrogen (H2) is a promising alternative to energy and environmentally intensive production. Bulk electronic and surface structures affect the charge transport efficiency and catalytic activity of the photoelectrode. Herein, we design and investigate a hematite (Fe2O3) nanorod photoelectrode with hafnium and titanium binary dopants for highly selective H2O2 production. The resultant photoanode shows a H2O2 yield of 0.41 μmol min–1 cm–2 at 1.5 VRHE with a Faradaic efficiency of 72.2%. Experimental investigations and theoretical calculations demonstrate the synergistic effect of Hf and gradient Ti doping on the hematite for the promising H2O2 performance. Hf doping effectively improves the crystallinity of Fe2O3, which favors improving the charge transport and reducing the charge recombination. Gradient Ti doping inhibits the collapse of the nanorod structure, increases the specific surface area, and introduces a large number of active sites on the surface. Ti- and Hf-codoped Ti/Hf:Fe2O3 photoanode improves the kinetics of H2O2 generation, leading to the high selectivity for H2O2 production and suppression of O2 production. This work provides the importance of hematite-based photoanodes toward the regulation of competition reactions for H2O2 production.