Synergistic mechanism of B doping and NiO loading on the excellent PEC performance and high stability of TiO2 nanotube photoanodes

The severe photogenerated charge recombination rate, poor visible light utilization and slow oxygen precipitation kinetics are the technical bottlenecks limiting the photo-electrolysis of TiO2 nanotube array (TNAs) photoanode for hydrogen production from water. To solve these problems, NiO nanoparticles were uniformly loaded into B-doped TNAs by the CV method. It is found that B-doping improves the energy band structure of TNAs, and doping-induced surface defects could become traps for photogenerated carriers to substantially improve the charge separation efficiency of the bulk phase. The P-N junctions formed between TiO2 anatase and NiO nanoparticles not only promoted the OER kinetics at the interface but also greatly improved the surface carrier separation efficiency of the catalyst, as well as ensured the stability and activity of the B-doping-induced surface defects. Moreover, the carrier concentration and visible light absorption properties of TNAs were enhanced and improved. Due to the synergistic effect of B doping and NiO loading, the bulk charge separation efficiency and surface charge separation efficiency of NiO/BT (B doping and NiO loading TNAs) were as high as 88.9 and 82.4%, respectively, at 1.23 V vs. RHE, and the photocurrent density reached 2.05 mA/cm2, which was 10 times higher than that of pure TNAs.