Two birds with one stone: Engineering polymeric carbon nitride with n-π∗ electronic transition for extending light absorption and reducing charge recombination
Gege Zhao, Bangwang Li, Xiaonan Yang, Xiaomeng Zhang, Zhongfei Li, Daochuan Jiang, Haiwei Du, Chuhong Zhu, Huiquan Li, Can Xue, Yupeng Yuan
Abstract
The weak visible light harvesting and high charge recombination are two main problems that lead to a low photocatalytic H2 generation of polymeric carbon nitride (p-CN). To date, the approaches that are extensively invoked to address this problem mainly rely on heteroatom-doping and heterostructures, and it remains a grand challenge in regulating dopant-free p-CN for increasing H2 generation. Here, we report utilizing the inherent n-π∗ electronic transition to simultaneously realize extended light absorption and reduced charge recombination on p-CN nanosheets. Such n-π∗ electronic transition yields a new absorption peak of 490 nm, which extends the light absorption edge of p-CN to approximately 590 nm. Meanwhile, as revealed by the photoluminescence (PL) spectra of p-CN at the single-particle level, the n-π∗ electronic transition gives rise to an almost quenched PL signal at room temperature, unravelling a dramatically reduced charge recombination. As a consequence, a remarkably improved photocatalytic performance is realized under visible light irradiation, with a H2 generation rate of 5553 μmol g−1∙h−1, ∼ 12 times higher than that of pristine p-CN (460 μmol∙g−1∙h−1) in the absence of the n-π∗ transition. This work illustrates the highlights of using the inherent n-π∗ electronic transition to improve the photocatalytic performance of dopant-free carbon nitrides.