Photocatalytic CO2 reduction is an effective way to simultaneously mitigate the greenhouse effect and the energy crisis. Herein, CdS hollow spheres, on which monolayer nitrogen‐doped graphene is in situ grown by chemical vapor deposition, are applied for realizing effective photocatalytic CO2 reduction. The constructed photocatalyst possesses a hollow interior for strengthening light absorption, a thin shell for shortening the electron migration distance, tight adhesion for facilitating separation and transfer of carriers, and a monolayer nitrogen‐doped graphene surface for adsorbing and activating CO2 molecules. Achieving seamless contact between a photocatalyst and a cocatalyst, which provides a pollution‐free and large‐area transport interface for carriers, is an effective strategy for improving the photocatalytic CO2 reduction performance. Therefore, the yield of CO and CH4, as dominating products, can be increased by four and five times than that of pristine CdS hollow spheres, respectively. This work emphasizes the importance of contact interface regulation between the photocatalyst and the cocatalyst and provides new ideas for the seamless and large‐area contact of heterojunctions.

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Solving energy and environmental problems through solar‐driven photocatalysis is an attractive and challenging topic. Hence, various types of photocatalysts have been developed successively to address the demands of photocatalysis. Graphene‐based materials have elicited considerable attention since the discovery of graphene. As a derivative of graphene, nitrogen‐doped graphene (NG) particularly stands out. Nitrogen atoms can break the undifferentiated structure of graphene and open the bandgap while endowing graphene with an uneven electron density distribution. Therefore, NG retains nearly all the advantages of original graphene and is equipped with several novel properties, ensuring infinite possibilities for NG‐based photocatalysis. This review introduces the atomic and band structures of NG, summarizes in situ and ex situ synthesis methods, highlights the mechanism and advantages of NG in photocatalysis, and outlines its applications in different photocatalysis directions (primarily hydrogen production, CO2 reduction, pollutant degradation, and as photoactive ingredient). Lastly, the central challenges and possible improvements of NG‐based photocatalysis in the future are presented. This study is expected to learn from the past and achieve progress toward the future for NG‐based photocatalysis.

Seeking for a suitable cocatalyst to realize highly efficient photocatalytic hydrogen (H2) production is a great challenge in the field of solar energy conversion. Herein, hollow cobalt sulfide (CoS x ) polyhedrons derived from ZIF-67 metal–organic frameworks were used as a cocatalyst to enhance the photocatalytic H2 generation performance of graphitic carbon nitride (g-C3N4). The polyhedral morphology with more exposed edges provides more surface active sites for H2 generation, while the interface between CoS x and g-C3N4 with intimate contact leads to better separation efficiency of photogenerated charge carriers. Moreover, the hollow structure not only favors mass diffusion/transfer, but also induces multiple reflections of light within the hollow cavity, enhancing the utilization efficiency of solar energy. As a result, the obtained CoS x /g-C3N4 composites showed excellent photocatalytic H2 generation activity, achieving a H2 evolution rate of 629 μmol g–1 h–1 under visible light (λ ≥ 400 nm), which was about 52 times higher than that achieved by pure g-C3N4. This work proves that hollow CoS x polyhedrons can be a potential substitute for noble metal cocatalysts for photocatalytic H2 generation.