Two-dimensional TiO₂-g-C₃N₄ with both Ti[sbnd]N and C[sbnd]O bridges with excellent conductivity for synergistic photoelectrocatalytic degradation of bisphenol A

TiO₂-mediated photoelectrocatalysis is emerging as a promising way to degrade refractory contaminates. Nevertheless, the concrete application of TiO₂ is seriously limited because of its poor conductivity, unexpected recombination of photoinduced charges, and broad bandgap (3.2 eV). In this work, two-dimensional (2D) TiO₂-g-C₃N₄ with both Ti[sbnd]N and C[sbnd]O bridges is successfully constructed and assembled with carbon fibers to realize efficient photoelectrochemical (PEC) pollutant degradation. Density functional theory (DFT) calculations suggest that the generated interface heterojunction of 2D TiO₂-g-C₃N₄ can provide quick charge separation and transfer via both Ti[sbnd]N and C[sbnd]O bridges, resulting in a prepared catalyst that can facilitate the effective separation and transportation of photoinduced electron-hole pairs. In addition, according to electrochemical impedance spectroscopy, the 2D TiO₂-g-C₃N₄ composition with the generated interface heterojunction reduces internal resistance and becomes more conducive to electrocatalysis compared with pure TiO₂ or g-C₃N₄. Using bisphenol A (BPA) as a typical refractory contaminate, the 2D TiO₂-g-C₃N₄/carbon fiber electrode exhibits a higher PEC activity, with reaction rates 1.7, 2.5, and 3 times faster than that of g-C₃N₄, TiO₂, and commercial P25, respectively. Furthermore, the greatest BPA degradation of the PEC system is much higher than the sum of the photocatalytic (PC) and electrocatalytic (EC) systems. Additionally, the enhanced activities of electrocatalysis and photocatalysis for the degradation of BPA is attributed to the collaboration of the interfacial effect and excellent electrical conductivity derived from the 2D structure of the TiO₂-g-C₃N₄ heterojunction. This study proposes a new tactic for the design and construction of photoelectrocatalysts via a synergistic interfacial effect to improve the photocatalytic and electrocatalytic degradation activities for refractory pollutants.