Vacancy-engineered graphitic carbon nitride for efficient photocatalytic H₂O₂ production with wastewater purification application

Photocatalytic production of hydrogen peroxide (H₂O₂) has emerged as a promising environmentally friendly and sustainable synthetic approach. But pristine graphitic carbon nitride (g-C₃N₄) suffers from rapid charge recombination and poor light utilization, limiting its efficiency for both H₂O₂ synthesis and downstream environmental applications. This review systematically examines vacancy engineering as an effective strategy to overcome these limitations in g-C₃N₄-based photocatalysts, with particular emphasis on their dual functionality in H₂O₂ production and water treatment applications. It begins by elucidating the fundamental mechanisms of photocatalytic H₂O₂ synthesis, followed by a comprehensive analysis of vacancy modulation strategies, from single nitrogen/carbon vacancies to synergistic hybrid systems. Beyond performance metrics, the practical potential of vacancy-engineered g-C₃N₄ is critically assessed in integrated water purification processes, including Fenton-like advanced oxidation and broad-spectrum antibacterial treatments, where in-situ generated H₂O₂ serves as a green oxidant. This review integrates fundamental and applied insights to guide high-performance g-C₃N₄ design for sustainable H₂O₂ synthesis and environmental remediation. © 2026 Elsevier Ltd.