As the world decides on the next giant step for the renewable energy revolution, scientists have begun to reinforce their headlong dives into the exploitation of solar energy. Hitherto, numerous attempts are made to imitate the natural photosynthesis of plants by converting solar energy into chemical fuels which resembles the “Z‐scheme” process. A recreation of this system is witnessed in artificial Z‐scheme photocatalytic water splitting to generate hydrogen (H2). This work outlines the recent significant implication of the Z‐scheme system in photocatalytic water splitting, particularly in the role of electron mediator and the key factors that improve the photocatalytic performance. The Review begins with the fundamental rationales in Z‐scheme water splitting, followed by a survey on the development roadmap of three different generations of Z‐scheme system: 1) PS‐A/D‐PS (first generation), 2) PS‐C‐PS (second generation), and 3) PS‐PS (third generation). Focus is also placed on the scaling up of the “leaf‐to‐tree” challenge of Z‐scheme water splitting system, which is also known as Z‐scheme photocatalyst sheet. A detailed investigation of the Z‐scheme system for achieving H2 evolution from past to present accompanied with in‐depth discussion on the key challenges in the area of Z‐scheme photocatalytic water splitting are provided.

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Graphitic carbon nitride (g‐C3N4) is a kind of ideal metal‐free photocatalysts for artificial photosynthesis. At present, pristine g‐C3N4 suffers from small specific surface area, poor light absorption at longer wavelengths, low charge migration rate, and a high recombination rate of photogenerated electron–hole pairs, which significantly limit its performance. Among a myriad of modification strategies, point‐defect engineering, namely tunable vacancies and dopant introduction, is capable of harnessing the superb structural, textural, optical, and electronic properties of g‐C3N4 to acquire an ameliorated photocatalytic activity. In view of the burgeoning development in this pacey field, a timely review on the state‐of‐the‐art advancement of point‐defect engineering of g‐C3N4 is of vital significance to advance the solar energy conversion. Particularly, insights into the intriguing roles of point defects, the synthesis, characterizations, and the systematic control of point defects, as well as the versatile application of defective g‐C3N4‐based nanomaterials toward photocatalytic water splitting, carbon dioxide reduction and nitrogen fixation will be presented in detail. Lastly, this review will conclude with a balanced perspective on the technical and scientific hindrances and future prospects. Overall, it is envisioned that this review will open a new frontier to uncover novel functionalities of defective g‐C3N4‐based nanostructures in energy catalysis.