Type II cuprous oxide/graphitic carbon nitride p-n heterojunctions for enhanced photocatalytic nitrogen fixation

Graphitic carbon nitride (CN) is a metal-free polymeric n-type semiconductor and a promising photocatalyst for dinitrogen fixation. However, modest solar spectrum utilization and poor charge separation limit its photocatalytic performance. Herein, we combined p-type Cu2O with n-type CN to create novel p-n heterojunction photocatalysts, which demonstrated greatly improved nitrogen reduction performance relative to pristine CN or Cu2O, and also excellent cyclic stability. The quantum efficiency of the compositionally optimized 0.6Cu2O/CN photocatalyst was 0.57%, which was approximately 5 times higher than that of Cu2O (0.1%). A NH3 production rate of 10 μmol h−1 was realized under visible light. The NH3 production activity remained high over 20 h of continuous testing. An in-depth exploration of the energy band structure of the photocatalyst allowed rationalization of the enhanced photocatalytic fixation performance in the p-n system, which guides the future design of improved nitrogen reduction photocatalysts.