An investigation into the enhancement of g-C3N4 photocatalytic performance by surface modification

Abstract

In this work, the enhancement of g-C3N4 photocatalytic performance by surface modification was investigated for two applications: photodegradation of tetracycline hydrochloride (TC) and photocatalytic hydrogen evolution. To study the effect of g-C3N4 on the photodegradation of TC, g-C3N4 samples were prepared by the hydrothermal process with different hydrolysis times and temperatures, namely CN-180-x and CN-200-6 and characterized by multiple physicochemical techniques. Compared to the CN, CN-180-6 possesses remarkable photocatalytic degradation efficiency at 97.17% towards TC removal in an aqueous solution. The high visible-light-induced photo-reactivity of CN-180-6 directly correlates to charge transfer efficiency, numerous structural defects with a high specific surface area, and sufficient O-functional groups over g-C3N4. However, hydrothermal treatment at a higher temperature or for a longer time additionally induces the growth of extended melem units on the surface of g-C3N4, resulting in the inhibition of the charge transfer. The hydrogen evolution production was enhanced through the synthesis of g-C3N4 catalysts co-doped with oxygen (O) and phosphorus (P). By using the doping process, controlled amounts of O-groups could be introduced into g-C3N4 without the growth of melem units as is the case with hydrothermal treatment. Furthermore, the substitution of nitrogen with P and O added into g-C3N4 enabled the separation of photogenerated charge carriers, inhibited the recombination of electron-hole pairs, and assisted the formation of Pt2+ for hydrogen evolution. As a result, O2.5¬PCNUPt showed the highest hydrogen evolution performance at 439.7 µmol. g‒1.h‒1.