Gradient Sulfur Doping Along Polymeric Carbon Nitride Films as Visible Light Photoanodes for the Enhanced Water Oxidation

Abstract Photoelectrochemical water splitting fulfils sustainable goal in the renewable H2 fuel production by storage of solar energy through chemical bonds. In the system, a rational design of a photoanode is the key to achieve an efficient solar water splitting, since the sluggish kinetic of oxygen evolution. Herein, polymeric carbon nitride based visible-light sensitive photoanodes are achieved with the gradient sulfur doping along the films. Subsequently, a gradual variation of the bandgap is formed. Therefore, on one hand, visible light absorption of the films is increased up to 2.55 eV. On the other hand, charge separation and transfer are promoted by virtue of the gradually varied electronic properties. As a result, the architecture of photoanode profits for water oxidation and leads the optimal photocurrent density ca. 110 μA/cm2 at 1.23 V vs reversible hydrogen electrode.