Electrochemical Fabrication of Ternary Black Ti‐Mo‐Ni Oxide Nanotube Arrays for Enhanced Photoelectrochemical Water Oxidation

Point defects play important and crucial roles in the design of high performance photocatalysts. We report on the electrochemical fabrication of black Ti−Mo‐Ni−O nanotubes as a promising electrode material for solar‐assisted water splitting. The ternary Ti−Mo‐Ni−O catalyst was annealed in hydrogen atmosphere to induce point defects in the material to enhance its conductivity, charge carriers density, and performance. The effect of annealing duration on the performance of ternary Ti−Mo‐Ni−O nanotube films was investigated. The hydrogen‐annealed nanotubes showed enhanced optical characteristics in the visible spectrum, which can be related to the formation of defect states upon hydrogen annealing. The 10 h‐annealed sample showed an exceptionally enhanced photocurrent density of ∼10 mA/cm2 with a remarkable open‐circuit voltage of ∼−1.0 VAg/AgCl under AM 1.5G illumination. This improved photocurrent is in agreement with the obtained 75 % incident‐photon‐to‐current‐conversion‐efficiency (IPCE), confirming the improved photoactivity of the hydrogen‐treated mixed oxide nanotubes. Point defects play important and crucial roles in the design of high performance photocatalysts. Black Ti−Mo‐Ni−O nanotubes are promising electrode materials for solar‐assisted water splitting. The hydrogen‐annealed nanotubes showed enhanced optical characteristics in the visible spectrum, which can be related to the formation of defect states upon hydrogen annealing. The 10 h‐annealed sample showed an exceptionally enhanced photocurrent density of ∼10 mA/cm2 with a remarkable open‐circuit voltage of ∼−1.0 VAg/AgCl under AM 1.5G illumination.