Primary graphitization of multi-functional dihydropyridine, a novel method for reconstructing a TiO2 surface to obtain high photocatalytic activity for hydrogen peroxide synthesis

Abstract

As a green and sustainable energy technology, converting solar energy into hydrogen peroxide (H₂O₂) chemical energy has become one of the key research fields of photocatalysis. It has been reported that TiO₂ has reached an excellent H₂O₂ productivity of 3.3 mM h⁻¹, and, therefore, there is value in using it for further research. Herein, a novel method for repairing and improving the surface of TiO₂ was developed using small organic molecules that can enter the nanopores of TiO₂ to form C, N, and O co-doped graphite-like hybrid structures. Thus, efficiently and conveniently, a multifunctional dihydropyridine with an electron-donating hydroxyl substituent successfully conducted thermally induced intermolecular condensation and subsequent in situ graphitization, resulting in efficient regulation of surficial properties. The results show that hybrid species enhanced the separation and transmission of photogenerated charges, reduced the photocatalytic effect for the decomposition of H₂O₂, and provided an effective channel for photocatalytic H₂O₂ synthesis. Under xenon lamp illumination, an initial rate of 10.22 mmol (h g)⁻¹ H₂O₂ was obtained, which exceeded that for all previously reported catalysts. In addition, ACMD successfully increased the light utilization efficiency of nano-TiO₂, with an apparent quantum efficiency (AQE) of 24.5% at 365 ± 5 nm and a solar-to-chemical conversion (SCC) efficiency of 2.18% under irradiation above 300 nm. Its visible light performance was significantly improved to afford 3.12 mmol (h g)⁻¹ H₂O₂ with an SCC of 1.17% under irradiation greater than 420 nm. Because of the diversity of such organic molecules, this method provides researchers with many opportunities to further optimize hybrid species on the surface of TiO₂, and, therefore, it is significant for the development of photocatalysts.