Plasma surface treatment facilitated visible light-driven H2 production over TiO2

TiO2 precursors were treated by plasma technology in three atmospheres (N2, Ar, H2). Interstitial N-doping can be facilely realized in N2 atmosphere, the light absorption range of N2-TiO2 is enlarged, and the surface oxygen vacancies (OVs) are significantly increased. Surface OVs enhance the efficient separation of photogenerated e−/h+ pairs in TiO2. The microscopic oxide layer on the surface of TiO2 is destroyed, bringing about Ti3+ defects and formation of more surface OVs in H2 and Ar atmosphere. Ti3+ defects, high concentration of surface OVs and the Ti3+-OVs defect energy level significantly reduce the photogenerated electron excitation energy. The photocatalytic H2 production activity of TiO2 treated via plasma technique in the different atmospheres was evaluated under visible light irradiation. Consequently, the H2 production efficiency on N2-TiO2 is 103.6 umolh−1 g−1, which is 2.1 times, 1.6 times, and 1.3 times of that on the pristine TiO2, H2-TiO2, and Ar-TiO2, respectively. The apparent quantum efficiency (AQE) of H2 generation on N2-TiO2 is 0.08%, which is 1.6 times of that over the reference TiO2 under 420 nm monochromatic light irradiation. The photocatalytic mechanisms for H2 production over all the photocatalysts were discussed according to a series of characterizations.