Abstract: Hydrogen peroxide (H₂O₂) serves as an environmentally benign oxidant, and its photocatalytic synthesis coupled with environmental remediation is an extremely attractive strategy. To address sluggish charge dynamics and surface reaction in conventional photocatalysts, two-dimensional tantalum carbide (Ta₂C) MXene was explored as an effective cocatalyst to engineer the interfacial electronic structure of graphitic carbon nitride (g-C₃N₄), enabling highly efficient H₂O₂ production and simultaneous tetracycline hydrochloride (TCH) degradation. Systematic characterization and theoretical calculations revealed that the significant work function difference between the two components induces Fermi level equilibration and facilitates built-in electric field formation, which drives directional photogenerated electron migration from g-C₃N₄ to Ta₂C, accelerating charge separation and suppressing charge recombination. The optimized g-C₃N₄/Ta₂C-6 (CT-6) composite achieved an H₂O₂ production rate of 4584.7 μmol g^-1 h^-1, together with 86.56% of TCH degradation within 1 h, markedly outperforming pristine g-C₃N₄. Mechanistic studies show that H₂O₂ is mainly produced through a two-step one-electron oxygen reduction pathway, and the reactive oxygen species generated in the reaction play a key role in TCH degradation. This study demonstrates the potential of Ta₂C as a non-noble-metal cocatalyst and establishes a clear correlation between interfacial electronic structure, charge transfer dynamics and photocatalytic reaction pathways in MXene-based heterojunctions, offering atomic-level insights and theoretical basis for the design of high-performance, multifunctional photocatalysts.

Key words: H₂O₂production, Graphitic carbon nitride, Ta₂C MXene, Cocatalyst