Bifunctional template-mediated synthesis of porous ordered g-C3N4 decorated with potassium and cyano groups for effective photocatalytic H2O2 evolution from dual-electron O2 reduction

[Display omitted] •Bifunctional KHCO3 template-mediated synthesis of porous and well-structured g-C3N4.•Cyano defects and K intercalation are introduced into g-C3N4 framework.•Catalysts owns tunable band structure, optimized charge transfer.•The mechanism is well studied by experiments and theoretical calculations.•The photocatalyst exhibits an excellent ability to produce H2O2 under visible light. The photocatalytic method to produce hydrogen peroxide (H2O2) as a substitute for fossil fuels has become a hot research topic. We herein propose cyano defect and potassium intercalation modified g-C3N4 photocatalysts in which the porous structure and crystallinity can be maintained relatively well. Simultaneously, the photocatalysts possess adjustable band structure, enhanced carrier transfer efficiency and highly selective dual-electron O2 reduction. The physicochemical properties and reaction mechanisms are well studied through the effective combination of experiments and theoretical calculations. The H2O2 yield of KDCN-0.2 (278.9 μmol L-1h−1) is approximately 4.3 times higher than that of original CN (65.2 μmol L-1h−1), and the energy conversion efficiency is also higher than many current CN-based photocatalysts. This work deepens the understanding of the mechanism of photocatalytic O2 reduction for H2O2 production and points out the promising direction for the design of novel CN-based photocatalysts with ideal properties in energy conversion and environmental applications.