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 photo-catalytic 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.