Efficient charge separation and transfer of a TaON/BiVO4 heterojunction for photoelectrochemical water splitting

The separation and transfer of photogenerated electron–hole pairs in semiconductors is the key point for photoelectrochemical (PEC) water splitting. Here, an ideal TaON/BiVO4 heterojunction electrode was fabricated via a simple hydrothermal method. As BiVO4 and TaON were in well contact with each other, high performance TaON/BiVO4 heterojunction photoanodes were constructed. The photocurrent of the 2-TaON/BiVO4 electrode reached 2.6 mA cm−2 at 1.23 V vs. RHE, which is 1.75 times as that of the bare BiVO4. TaON improves the PEC performance by simultaneously promoting the photo-generated charge separation and surface reaction transfer. When a Co-Pi co-catalyst was integrated onto the surface of the 2-TaON/BiVO4 electrode, the surface water oxidation kinetics further improved, and a highly efficient photocurrent density of 3.6 mA cm−2 was achieved at 1.23 V vs. RHE. The largest half-cell solar energy conversion efficiency for Co-Pi/TaON/BiVO4 was 1.19% at 0.69 V vs. RHE, corresponding to 6 times that of bare BiVO4 (0.19% at 0.95 V vs. RHE). This study provides an available strategy to develop photoelectrochemical water splitting of BiVO4-based photoanodes.