Thinned g-C3N4 nanosheets with microdopants of cucurbit[7]uril to improve photoelectrochemical water-splitting

Abstract

Utilizing solar energy to generate hydrogen through photoelectrochemical (PEC) water splitting is considered as the most efficient method and sustainable pathway. Graphitic carbon nitride (g-C₃N₄), as a candidate for photoelectrochemical catalysts, exhibits the drawbacks including small specific surface area and high complexity of photogenerated electron-hole pairs. With supramolecular encapsulation of melamine guest within cucurbit[7]uril, a new process for thinned and nitrogen-doped g-C₃N₄-0.04 % nanosheets are developed, and the photoelectrocatalytic activity is obviously improved on the surface. A photocathode with the prepared g-C₃N₄-0.04 % nanosheets produce more than twice efficiency of pristine g-C₃N₄ for water splitting, and the incident photon-to-current conversion efficiency (IPCE) is increased by a factor of about 10 under simulated conditions of sunlight at AM 1.5 G (100 mW/cm²). The improved performance should be the results of the thinned layers by introduction of the macrocyclic compound in g-C₃N₄ nanosheets, which reduce the charge transfer resistance, and inhibit the complexation of the photogenerated electron pairs, to prolong the lifetime of the electron, and facilitate the ability of the electron transport with an increase in current. On the other hand, the specific surface area is improved in the g-C₃N₄-0.04 % nanosheets to expose more reactive sites, and the microdopant of cucurbit[7]uril provides more active nitrogen sites, to enhance the photocatalysis.