Recent advancements in graphitic carbon nitride based direct Z- and S-scheme heterostructures for photocatalytic H2O2 production

Abstract

Escalating global energy demands and the pressing need for sustainable and environmentally friendly energy sources have intensified research in the field of renewable energy, particularly solar energy. Hydrogen peroxide (H₂O₂), as a green and sustainable oxidant, is important for environmental remediation, chemical synthesis, and as a next-generation energy fuel. Solar energy harnessed in photocatalysis enables light-driven H₂O₂ production, offering an eco-friendly synthesis method. High-performance photocatalysts are essential for achieving viable solar H₂O₂ synthesis. Photocatalysis, particularly using g-C₃N₄, a visible-light-responsive metal-free semiconductor, presents a promising avenue for future large-scale H₂O₂ production. This is due to its unique properties, such as its oxygen-reduction-friendly conduction band, tuneable molecular structure, stability, cost-effectiveness, Earth abundance, facile synthesis, non-toxicity, numerous active sites, surface imperfections and high selectivity for H₂O₂ generation, making it a vital material in the renewable energy sector. However, challenges like rapid exciton recombination, limited light absorption capacity, suboptimal electrical conductivity, low specific surface area, and slow water oxidation kinetics need to be addressed to enhance its catalytic efficiency. Hence, the development of direct Z- or more relevant S-scheme heterostructures of g-C₃N₄ could promote the charge carrier separation efficiency, optimize the redox potential and improve the photocatalytic activity significantly. This review focuses on g-C₃N₄ as a photocatalyst, emphasizing its properties and the potential of direct Z- and S-scheme heterojunctions in photocatalytic H₂O₂ production. It introduces the background and surge in research on these heterojunctions, covers design principles, charge transfer mechanisms, advanced characterization methods, driving force enhancement strategies, Fermi level adjustment tactics, and principles of H₂O₂ production, including formation pathways, kinetics, detection, and performance evaluation. It offers insights into g-C₃N₄-based heterostructures’ potential for application in H₂O₂ production and concludes with future prospects and challenges, focusing on strategies to enhance yields and suggesting new research directions.