Dual Hole Transport Layers Heterojunction and Band Alignment Engineered Mo:BiVO 4 Photoanodes for Efficient Water Splitting.

BiVO 4 -based photoanode is one of the most promising photoanodes for photoelectrocatalytic water splitting. However, the serious problem of interface charge recombination limits its further development. Here, a Mo:BiVO 4 /NiO x /CPF-TCzB/NiCoBi photoanode is constructed with double hole transport layer and an energy level gradient to achieve an effective photo-generated holes extraction and accumulation at the surface electrocatalyst. The conjugated polycarbazole framework CPF-TCzB is used as hole transport layer to eliminate the charge recombination center between Mo:BiVO 4 and NiCoBi electrocatalyst and realize the extraction and storage of photo-generated hole; NiO x nanoparticles are further inserted between Mo:BiVO 4 and CPF-TCzB to form a gradient energy level, eliminating the energy level barrier and optimizing band alignment. As a result, Mo:BiVO 4 /NiO x /CPF-TCzB/NiCoBi achieves a much higher photocurrent densities of 3.14 mA cm -2 than that of Mo:BiVO 4 (0.42 mA cm -2 ) at 0.6 V versus RHE. This work provides an specific way to adjust the band structure of BiVO 4 -based photoanodes and realize efficient hole extraction and storage for PEC water splitting.