Molecular anchoring induced charge transfer pathway conversion from p–n to S-scheme heterojunctions for boosting photocatalytic hydrogen evolution and N2 fixation

The p–n type charge transfer pathway plays an active role in efficient carrier separation and enhancement of photocatalytic activity, but it will also reduce the redox ability of photogenerated carriers. Herein, the anchored amino molecular layer acts as a heterojunction conversion switch to transform Cu2O/T-N from a p–n to an S-scheme heterojunction. Following this transformation, the redox ability of carriers can be dramatically enhanced: the reduction potential of photogenerated electrons increases from −0.49 eV to −1.68 eV, and the oxidation potential of photogenerated holes increases from 0.32 eV to 2.33 eV. Therefore, the optimized Cu2O/T-N S-scheme heterojunction photocatalyst exhibits superior photocatalytic performance for hydrogen evolution (up to 41.85 mmol g−1, 64 times higher than that of pure TiO2) and nitrogen fixation (as high as 18 mmol gCu2O−1 h−1). Moreover, the post-conversion carrier transfer pathway also prevents the accumulation of holes on Cu2O, alleviating the photocorrosion caused by hole oxidation. Hence, the catalytic activity remains stable during photocatalytic cycling for up to 50 h. This study provides a straightforward and practical method for enhancing the redox capacity of photocatalysts.