Dual Hole Transport Layers Heterojunction and Band Alignment Engineered Mo:BiVO₄ Photoanodes for Efficient Water Splitting

BiVO₄-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:BiVO₄/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:BiVO₄ and NiCoBi electrocatalyst and realize the extraction and storage of photo-generated hole; NiO_x nanoparticles are further inserted between Mo:BiVO₄ and CPF-TCzB to form a gradient energy level, eliminating the energy level barrier and optimizing band alignment. As a result, Mo:BiVO₄/NiO_x/CPF-TCzB/NiCoBi achieves a much higher photocurrent densities of 3.14 mA cm^-2 than that of Mo:BiVO₄ (0.42 mA cm^-2) at 0.6 V versus RHE. This work provides an specific way to adjust the band structure of BiVO₄-based photoanodes and realize efficient hole extraction and storage for PEC water splitting.