Since the first discovery of solar-driven water splitting catalyzed by TiO₂ semiconductors, extensive research works have been devoted over the decades. Currently, the design of a photocatalyst with dual redox potential is of prominent interest to fully utilize both photogenerated electrons and holes in the redox reactions. Among all, the coproduction of H₂ and O₂ from water using metal-free carbon nitride (g-C₃N₄) has been viewed as a rising star in this field. However, the hole-mediated oxidation reaction is commonly recognized as the rate-determining step, which drastically leads to poor overall water splitting efficiency. On top of that, rapid recombination and undesirable back reaction appeared as one of the challenging parts in overall water splitting. In this review, the up-to-date advances in modified g-C₃N₄-based photocatalysts toward efficient overall water splitting are summarized, which are mainly classified into structural and defect engineering, single-atom catalysis, cocatalyst loading, and heterojunction construction. This review also addresses the underlying idea and concept to tackle the aforementioned problem with the use of emerging modification strategies, hence serving as the guiding star for future research. Despite the outstanding breakthrough thus far, critical recommendations related to g-C₃N₄ photocatalytic systems are prospected to pave the way toward the implementation in the practical energy production process.

With the fast-pace digitalization evolution in the current generation’s lifestyle and the industry revolution, the energy demand has been skyrocketed. Recently, the two-dimensional (2D) bismuth-based nanomaterials emerged as a promising photocatalyst candidate in solar fuel conversion, not only for its exceptional light absorption capability and tunable optical properties, but it also can be synthesized into diverse variety of nanomaterials with different ranges of potential gap and band position to fulfill the potential requirement of wide range of photocatalytic reaction. Yet, the weak light harvesting ability and ultrafast charge recombination has restricted its potential in commercial application. Thus, recent researches have been focusing on tackling these issues by incorporating some modification strategies such as heteroatom doping, vacancy engineering, facet engineering, bismuth rich strategy and heterojunction engineering. Herein, this review article presents the state-of-the-art modifications on 2D bismuth-based parent material, specifically on the relationship between each of the modification strategy on the electronic properties and surface chemistry in achieving boosted photocatalytic performance. In the view of the unique charge interaction between two semiconductors with different dimensions, we systematically discuss the rational heterostructure design from the dimensionality perspective, namely, point-to-face, line-to-face, face-to-face, and bulk-to-face in solar fuel conversion to provide inspiring insights for future interface engineering. Finally, the challenges and the future research outlook in the solar-to-fuel conversion are highlighted to push forward the design of high-performance bismuth-based photocatalyst in realizing commercial-scale solar-to-fuel conversion.