Fabrication of TiO 2 on porous g-C 3 N 4 by ALD for improved solar-driven hydrogen evolution.

Porous graphitic carbon nitride (P-g-C 3 N 4 ) thin sheets were fabricated by a one-step calcination of a mixture of urea, melamine, and ammonia chloride at 550 °C. P-g-C 3 N 4 showed 48% higher photocatalytic H 2 production from methanol aqueous solution than conventional urea-derived graphitic carbon nitride (g-C 3 N 4 ) because the existence of numerous pores reduces the recombination rate of charge carriers. In order to further enhance the photocatalytic activity, TiO 2 was uniformly deposited on P-g-C 3 N 4 by 60-300 cycles of atomic layer deposition (ALD) to form the TiO 2 @P-g-C 3 N 4 composite. They exhibited much higher photocatalytic hydrogen production rates than both TiO 2 and P-g-C 3 N 4 . Among all composites, the sample deposited with 180 ALD cycles of TiO 2 showed the highest H 2 production because of optimal diffusion length for electrons and holes. It also performed better than the sample of g-C 3 N 4 deposited with 180 cycles of TiO 2 .