Developing low-cost, efficient, and stable photocatalysts is one of the most promising methods for large-scale solar water splitting. As a metal-free semiconductor material with suitable band gap, graphitic carbon nitride (g-C₃N₄) has attracted attention in the field of photocatalysis, which is mainly attributed to its fascinating physicochemical and photoelectronic properties. However, several inherent limitations and shortcomings—involving high recombination rate of photocarriers, insufficient reaction kinetics, and optical absorption—impede the practical applicability of g-C₃N₄. As an effective strategy, vacancy defect engineering has been widely used for breaking through the current limitations, considering its ability to optimize the electronic structure and surface morphology of g-C₃N₄ to obtain the desired photocatalytic activity. This review summarizes the recent progress of vacancy defect engineered g-C₃N₄ for solar water splitting. The fundamentals of solar water splitting with g-C₃N₄ are discussed first. We then focus on the fabrication strategies and effect of vacancy generated in g-C₃N₄. The advances of vacancy-modified g-C₃N₄ photocatalysts toward solar water splitting are discussed next. Finally, the current challenges and future opportunities of vacancy-modified g-C₃N₄ are summarized. This review aims to provide a theoretical basis and guidance for future research on the design and development of highly efficient defective g-C₃N₄.

In recent years, Janus two-dimensional (2D) materials have received extensive research interests because of their outstanding electronic, mechanical, electromechanical, and optoelectronic properties. In this work, we explore the structural, electromechanical, and optoelectronic properties of a novel hypothesized Janus InGaSSe monolayer by means of first-principles calculations. It is confirmed that the Janus InGaSSe monolayer indeed show extraordinary charge transport properties with intrinsic electron mobility of 48 139 cm²/(V·s) and hole mobility of 16 311 cm²/(V·s). Both uniaxial and biaxial strains can effectively tune its electronic property. Moreover, the Janus InGaSSe monolayer possesses excellent piezoelectric property along both in-plane and out-of-plane directions. The results of this work imply that the Janus InGaSSe monolayer is in fact an efficient photocatalyst candidate, and may provide useful guidelines for the discovery of other new 2D photocatalytic and piezoelectric materials.In recent years, Janus two-dimensional (2D) materials have received extensive research interests because of their outstanding electronic, mechanical, electromechanical, and optoelectronic properties. In this work, we explore the structural, electromechanical, and optoelectronic properties of a novel hypothesized Janus InGaSSe monolayer by means of first-principles calculations. It is confirmed that the Janus InGaSSe monolayer indeed show extraordinary charge transport properties with intrinsic electron mobility of 48 139 cm²/(V·s) and hole mobility of 16 311 cm²/(V·s). Both uniaxial and biaxial strains can effectively tune its electronic property. Moreover, the Janus InGaSSe monolayer possesses excellent piezoelectric property along both in-plane and out-of-plane directions. The results of this work imply that the Janus InGaSSe monolayer is in fact an efficient photocatalyst candidate, and may provide useful guidelines for the discovery of other new 2D photocatalytic and piezoelectric materials.