Temperature-controlled ultra-high hydrogen evolution photocatalytic activity of cadmium sulfide without cocatalysts

Abstract

Photocatalytic water spitting is one way of hydrogen production from energy conservation and emission reduction. However, the activities of most photocatalytic materials need to be enhanced by cocatalysts. In this study, we explored to control the photocatalytic hydrogen evolution (PHE) ability of cadmium sulfide (CdS) without any cocatalysts by temperature and largely improve its photocatalytic ability. It was experimentally found the activity of CdS without cocatalysts under heating conditions (<100 °C) was much higher than that at room temperature, and increased first and then decreased, with a maximum at 50 °C (169716 umol/h, 68.2 % , λ = 450 nm). Therefore, it is convenient to control the hydrogen production activity of CdS by temperature. The large increment of photocatalytic activity was realized because the temperature complemented the shortcomings of semiconductors in light absorption, and together with light radiation, increased the electron migration rate and density, quantity of surface adsorbed H₃O⁺ and number of active sites, prolonged the living of electrons, and reduced the overpotential of water splitting and the reverse reactions. Heating brings the above advantages, but also exacerbates the recombination of electron-hole pairs. Therefore, the activity shows an extreme value along with the temperature rise. This work experimentally proves temperature control is one of the most efficient and simple ways to largely enhance the PHE ability.

Keywords: CdS; No co-catalyst; PHE; Temperature control.