Preparation of nickel-bismuth titanates enhanced visible-light photosensitivity and their photocatalytic properties for hydrogen generation by plasma cracking

Nickel-bismuth titanate was newly synthesized to develop a photocatalyst with better visible-light sensitivity than nickel titanate, which is known among perovskites to have high photocatalytic activity in visible light. Compared to nickel titanate, nickel-bismuth titanate prepared by the solvothermal method combined with the sol-gel method exhibited superior light absorption ability in the UV and visible light regions. The band gap energy of nickel titanate was 2.48 eV, whereas that of nickel-bismuth titanate was lower at 2.41 eV. The photocatalytic activity was evaluated by applying nickel-bismuth titanate to the liquid-phase plasma-cracking process of ammonia water for hydrogen generation. When the liquid plasma was discharged into ammonia water, a strong emission spectrum was observed under both UV and visible light. A strong emission peak related to hydrogen production was observed at 656 nm. The hydrogen production rate from the cracking of ammonia water under liquid plasma radiation was higher for nickel-bismuth-titanate than for nickel titanate. Among the nickel-bismuth titanates, Ni_0.9Bi_0.1TiO₃ showed the highest absorption capacity at 656 nm visible light and the narrowest band gap, indicating an excellent hydrogen production rate.