Fabrication Of CoTiO₃/g-C₃N₄ Hybrid Photocatalysts And Their Photocatalytic Performance

Since the overwhelming problems of environmental pollution and energy consumption, photocatalysis has become one of the most promising technologies. Herein, H2 evolution from photocatalytic water splitting has become a research hotspot. Among numerous photocatalysts, the Z-scheme heterogeneous photocatalysts are considered to be able to not only promote the separation efficiency of photogenerated electron-hole pairs, but also preserve excellent redox ability. In this work, a novel direct Z-scheme CoTiO3/g-C3N4 (CT-U) photocatalytic system with different weight percentages of CoTiO3 was synthesized using a facile in-situ growth method for H2 evolution by water splitting. Meanwhile, the charge separation and electron transport mechanism was in-depth investigated. The main research conclusions are as follows:(1) The pure CoTiO3 was prepared by sol-gel method and the heterostructure CT-U composites were successfully fabricated by calcination of the mixture of preformed CoTiO3 and urea (precursor of g-C3N4), with effectively intimate CoTiO3 (104)/g-C3N4 interfaces linked through the Co-O-N or Ti-O-N bond.(2) Under an optimal experimental condition, the most enhanced H2 evolution rate of 858 umol·h-l·g-1 and high quantum efficiency (38.4% at 365 nm,3.23% at 420 ± 20 nm) are achieved at an optimal 0.15% CT-U. Meanwhile, the 0.15% CT-U sample exhibits good photocatalytic stability after four cycling H2 evolution.(3) The direct Z-scheme mechanism was proposed and further evidenced by PL, transient photocurrent measurements and ESR analysis of active oxygen species. As a result, the Z-scheme type CoTiO3/g-C3N4 composite photocatalyst possesses an improved separation of photogenerated electron-hole pairs by accelerating the interfacial charge earrier recombination, resulting in a strong redox ability for enhanced H2 evolution from water splitting.