Synthesis of synergetic phosphorus and cyano groups (-C equivalent to N) modified g-C3N4 for enhanced photocatalytic H-2 production and CO2 reduction under visible light irradiation

Graphitic carbon nitride (g-C3N4) has become an attractive photocatalyst for solar energy conversion owing to its numerous advantages. Due to insufficient solar-light absorption and fast photogenerated carriers recombination, the photocatalytic activity of traditional g-C3N4 material is unsatisfactory. In this work, P element and cyano groups (C equivalent to N) incorporated into the g-C3N4 framework is successfully fabricated by heat treatment of the mixed g-C3N4 and NaH2PO2. The cyano groups (-C equivalent to N) originated from the de-protonation of -C-NH2 can enhance the light absorption and act as strong electron-withdrawing groups, which can promote the efficient separation of photo-generated electron-hole pairs. The P element doping can enhance the visible light absorption, shorten the band gap and suppress the recombination of photo-induced carriers. The synergistic effect of -C equivalent to N functional groups and P element doping results in a 6.7 times enhanced photocatalytic H-2 production activity and 1.58 times enhanced photocatalytic CO2 reduction activity than that of pristine g-C3N4. Experimental analysis indicates that the enhanced photocatalytic performance is mainly attributed to the enhanced light absorption and charge separation. Our work provides a new thought to design other high performance and low-cost g-C3N4-based photocatalytic materials for solar energy conversion.