A BiVO4/Bi2Mo2O9 heterostructure towards oriented charge transfer for efficient photoelectrochemical water oxidation

The sluggish transfer of photogenerated charges is an intrinsic problem in the photoelectrochemical (PEC) conversion of solar energy into chemical energy. Constructing nanostructured heterostructure photoelectrodes is one of the most effective strategies for achieving energetic charge transfer kinetics. Herein, we fabricate a type II heterostructure film of BiVO4/Bi2Mo2O9 for PEC water splitting using the successive ionic layer adsorption and reaction (SILAR) method. Owing to the work function difference of similar to 230 mV between the two semiconductors, free electrons will flow from Bi2Mo2O9 to BiVO4, causing positive charges to accumulate on the Bi2Mo2O9 side and negative charges on the BiVO4 side. This charge redistribution induces a built-in electric field pointing from Bi2Mo2O9 to BiVO4, facilitating the separation of photogenerated electrons and holes. Consequently, the corresponding photocurrent density in the BiVO4/Bi2Mo2O9 photoanode reaches 0.61 mA cm(-2), which is 3.4 times that of bare Bi2Mo2O9 (0.18 mA cm(-2)) at 1.23 V vs. the Reversible Hydrogen Electrode (RHE). The interface charge interaction results in upward and downward band bending toward the interface for Bi2Mo2O9 and BiVO4 and also leads to enhanced oxidation kinetics (70.1%) and high photovoltage (340 mV).