Preparation of Carbon-Rich g-C3N4 Nanosheets with Enhanced Visible Light Utilization for Efficient Photocatalytic Hydrogen Production

Exfoliation of layered bulk g-C3N4 (CNB) to thin g-C3N4 sheets in nanodomains has attracted much attention in photocatalysis because of the intriguing properties of nanoscaled g-C3N4. This study shows that carbon-rich g-C3N4 nanosheets (CNSC) can be easily prepared by self-modification of polymeric melon units through successively thermally treating bulk g-C3N4 in an air and N-2 atmosphere. The prepared CNSC not only retain the outstanding properties of nanosheets, such as large surface area, high aspect ratios, and short charges diffusion distance, but also overcome the drawback of enlarged bandgap caused by the quantum size effect, resulting in an enhanced utilization of visible light and photoinduced electron delocalization ability. Therefore, the as-prepared CNSC show a high hydrogen evolution rate of 39.6 mu mol h(-1) with a turnover number of 24.98 in 1 h at lambda > 400 nm. Under irradiation by longer wavelength of light (lambda > 420 nm), CNSC still exhibit a superior hydrogen evolution rate, which is 72.9 and 5.4 times higher than that of bulk g-C3N4 and g-C3N4 nanosheets, respectively.