A BiVO 4 /Bi 2 Mo 2 O 9 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 BiVO 4 /Bi 2 Mo 2 O 9 for PEC water splitting using the successive ionic layer adsorption and reaction (SILAR) method. Owing to the work function difference of ∼230 mV between the two semiconductors, free electrons will flow from Bi 2 Mo 2 O 9 to BiVO 4 , causing positive charges to accumulate on the Bi 2 Mo 2 O 9 side and negative charges on the BiVO 4 side. This charge redistribution induces a built-in electric field pointing from Bi 2 Mo 2 O 9 to BiVO 4 , facilitating the separation of photogenerated electrons and holes. Consequently, the corresponding photocurrent density in the BiVO 4 /Bi 2 Mo 2 O 9 photoanode reaches 0.61 mA cm −2 , which is 3.4 times that of bare Bi 2 Mo 2 O 9 (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 Bi 2 Mo 2 O 9 and BiVO 4 and also leads to enhanced oxidation kinetics (70.1%) and high photovoltage (340 mV).