Point defect engineering of elemental phosphorus for photocatalytic hydrogen evolution

Red phosphorus (RP) has been demonstrated for photocatalytic hydrogen evolution (PHE) in recent years. Realistically, P vacancy (V_P) defects are present in RP. The constructive or detrimental influences of such defects on the photocatalytic activity of RP should be revealed as the understanding shall provide a platform for further improvement. Herein, we for the first time establish a comprehensive understanding of the crucial relationships between the intrinsic V_P defects and the charge dynamics together with the photocatalytic performance in RP. Two main findings are achieved: i) V_P-induced deep charge trapping effect is revealed to lead to a severe loss of active electrons during the H⁺ reduction reaction, resulting in the inferior PHE performance of RP. ii) O doping in the V_P sites is demonstrated to be an effective strategy for eliminating the detrimental V_P defect states, leading to a long-lived free electron lifetime in RP for enhanced PHE performance. The point defect engineering of RP applied in this study paves a promising way in tuning the physicochemical properties of RP and other elemental-based materials for various applications.