Construction of ternary TiO2/CdS/IrO2 heterostructure photoanodes for efficient glycerol oxidation coupled with hydrogen evolution

Abstract

TiO2/CdS heterostructure has been widely investigated as a potential photoanode for photoelectrochemical (PEC) water splitting for hydrogen evolution. However, the efficiency and stability still remains challenging due to the sluggish reaction dynamics for water oxidation and easy photocorrosion of CdS. Here we report a ternary TiO2/CdS/IrO2heterosturcture with IrO2 as a hole transport layer for PEC glycerol oxidation coupled with hydrogen evolution. The photocurrent density of the optimized TiO2/CdS photoanode is 18.8 mA cm-2 (1.23 V vs. RHE), which is about 10.6 times higher than that of the pristine TiO2. It is found that most of the glycerol was converted to formic acid (FA) on the TiO2/CdS surface with the production rate ~603.0 mmol m-2 h-1.The average H2 production rate reaches 1574.5 mmol m-2 h-1. After loading IrO2 nanoparticles, the products for glycerol oxidation remain unchanged with the production rate of FA reaching 863.4 mmol m-2 h-1, while the hydrogen production rate is increased to 2345.2 mmol m-2 h-1 due to the improved stability. The results show that the obtained TiO2/CdS/IrO2 heterostructure can effectively oxidize glycerol to value-added chemicals. The enhanced PEC performance and stability of the TiO2/CdS/IrO2 photoanode can be ascribed to the greatly enhanced electrode/electrolyte interfacial carrier injection efficiency, caused by the fast glycerol oxidation dynamics and intimate contact. This work provides novel ideas to construct high-efficient PEC systems for both clean energy production and high-value chemicals.