Photo-chemical property evolution of superior thin g-C3N4 nanosheets with their crystallinity and Pt deposition

Abstract

The crystallinity and composition of superior thin g-C3N4 nanosheets were adjusted at different temperature settings to study property evolution via a two-step thermal polymerization procedure. g-C3N4 sample prepared at 600 °C shows high N/C ratio and amorphous structure while a crystalline g-C3N4 sample with C/N ratio of nearly 0.75 was obtained at 750 °C. The band gap varies for each type of g-C3N4 sample and photodegradation kinetics were examined to be related to the crystallinity of the g-C3N4 sample. The RhB photocatalytic degradation plots for g-C3N4 nanosheets samples prepared at more than 600 °C are fitted using the pseudo-first-order model while the reaction for bulk g-C3N4 sample prepared at 550 °C follows zero-order kinetics. This phenomenon is ascribed to the varying surface states of the g-C3N4 samples. g-C3N4 nanosheets prepared at 700 °C showed the best photocatalytic performance, in which the sample with both amorphous and crystalline structural features is assumed to be amorphous/crystalline homojunctions. Moreover, Pt deposition confirms that g-C3N4 nanosheets prepared at 700 °C reveal the highest photocatalytic H2 evolution rate of 4892 μmol/hg which is about 21 times high compared with amorphous g-C3N4 nanosheets prepared at 600 °C.