Sparked by natural photosynthesis, solar photocatalysis using metal‐free graphitic carbon nitride (g‐C3N4) with appealing electronic structure has turned up as the most captivating technique to the quest for sustainable energy generation and pollution‐free environment. Nonetheless, low‐dimensional g‐C3N4 is thwarted from sluggish kinetics and rapid recombination of photogenerated carriers upon light irradiation. Among multifarious modification strategies, engineering 2D cocatalysts is anticipated to accelerate redox kinetics, augment active sites and ameliorate electron–hole separation of 2D g‐C3N4 for boosted activity thanks to its face‐to‐face contact surface. It is of timely and technological significance to review the 2D/2D interfaces with state‐of‐the‐art 2D cocatalysts, spanning from carbon‐containing to phosphorus‐containing, metal dichalcogenide, and other cocatalysts. Fundamental principles for each photocatalytic application will be introduced. Thereafter, the recent advances of 2D/2D cocatalyst‐mediated g‐C3N4 systems will be critically evaluated based on their interfacial engineering, emerging roles, and impacts toward stability and catalytic efficiency. Importantly, mechanistic insights into the charge dynamics and structure–performance relationship will be deciphered. Last, noteworthy research directions are prospected to deliver insightful ideas for future development of g‐C3N4. Overall, this review is anticipated to serve as a scaffold and cornerstone in designing dimensionality‐dependent 2D cocatalyst‐assisted g‐C3N4 toward renewable energy and ecologically green environment.

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Direct conversion of waste CO2 into CH3OH by solar irradiation has emerged as the most enthralling alternative to conventional steam methane reforming, which reduced the concentration of greenhouse gases and the consumption of fossil resources. A cradle-to-gate life cycle assessment was carried out to assess the environmental feasibility of implementing the current g-C3N4-based photocatalytic CO2 reduction system based on 1 kg CH3OH production. It was observed that the emerging photocatalytic CH3OH system induced 68 and 53% less carbon footprint and fossil usage, respectively, in producing the same amount of CH3OH as compared to the conventional approach. The CO2 reduction reaction step was identified as the main contributor in photocatalytic system, which accounted for more than 50% of the total environmental impact scores. In the conventional system, the score points of global warming and fossil depletion contributed the most by the product purification and desulfurization step, respectively. In addition, sensitivity analysis manifested that the lowest environmental burden of 46.50 kg of CO2 equiv carbon emission and 15.27 kg oil equiv fossil consumption was obtained in the photocatalytic CH3OH system upon replacing fossil-based energy with hydro-powered electricity. These results suggest a potent replacement of the incumbent industry system for the amelioration of climate benefits and resource conservation with the advanced development of the photocatalytic system.

Since the first discovery of solar-driven water splitting catalyzed by TiO 2 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 H 2 and O 2 from water using metal-free carbon nitride (g-C 3 N 4 ) 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-C 3 N 4 -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-C 3 N 4 photocatalytic systems are prospected to pave the way toward the implementation in the practical energy production process.