Enhanced Charge Transfer via Heterogeneous Doping Promotes Hematite Photoelectrodes for Efficient Solar H<sub>2</sub>O<sub>2</sub> Synthesis
Fei Guo, Jinwei Bai, Rui‐Ting Gao, Kerong Su, Yang Yang, Xianhu Liu, Limin Wu, Lei Wang
Abstract
Photoelectrochemical (PEC) water splitting into hydrogen peroxide (H 2 O 2 ) and hydrogen (H 2 ) 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 (Fe 2 O 3 ) nanorod photoelectrode with hafnium and titanium binary dopants for highly selective H 2 O 2 production. The resultant photoanode shows a H 2 O 2 yield of 0.41 μmol min –1 cm –2 at 1.5 V RHE 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 H 2 O 2 performance. Hf doping effectively improves the crystallinity of Fe 2 O 3, 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:Fe 2 O 3 photoanode improves the kinetics of H 2 O 2 generation, leading to the high selectivity for H 2 O 2 production and suppression of O 2 production. This work provides the importance of hematite-based photoanodes toward the regulation of competition reactions for H 2 O 2 production.