Dual-functional photocatalysis for hydrogen evolution from industrial wastewaters

Abstract

Realization of hydrogen economy requires an environmental and economic method for hydrogen (H₂) evolution. Dual-functional photocatalysis, that is, producing H₂ from industrial wastewaters, may be the most ideal. However, it seems almost impossible to achieve dual-functional photocatalysis because of the difficulty in the simultaneous existence of photocatalytic pollutant degradation (PDR) and H₂ evolution reactions (HER) in one system. All previous designs show that either HER or PDR is inhibited due to the insufficient management of the photo-generated electrons (e⁻) and holes (h⁺). To overcome this issue, we consider that both PDR and HER could be improved simultaneously by employing a suitable photocatalyst whose main active species in PDR are h⁺. In this case, e⁻ and h⁺ can play their own roles in accomplishing HER and PDR, respectively, via the charge spatial separation in the selected photocatalyst. Herein, Cu₂O polyhedrons are constructed as a proof-of-concept example. A favorable dual-functional photocatalytic performance is achieved by the Cu₂O cubooctahedrons. Furthermore, an appropriate pollutant concentration is significant for the optimization of both HER and PDR performances due to the competition between H atom adsorption and pollutant molecule adsorption on the surfaces of the photocatalyst. This advance provides the H₂ evolution technology with a more environmental and economic method.