Synergetic enhancement of surface reactions and charge separation over holey C3N4/TiO2 2D heterojunctions

Efficient charge separation and rapid interfacial reaction kinetics are crucial factors that determine the efficiency of photocatalytic hydrogen evolution. Herein, a fascinating 2D heterojunction photocatalyst with superior photocatalytic hydrogen evolution performance - holey C3N4 nanosheets nested with TiO2 nanocrystals (denoted as HCN/TiO2) - is designed and fabricated via an in situ exfoliation and conversion strategy. The HCN/TiO2 is found to exhibit an ultrathin 2D heteroarchitecture with intimate interfacial contact, highly porous structures and ultrasmall TiO2 nanocrystals, leading to drastically improved charge carrier separation, maximized active sites and the promotion of mass transport for photocatalysis. Consequently, the HCN/TiO2 delivers an impressive hydrogen production rate of 282.3 μmol h-1 per 10 mg under AM 1.5 illumination and an apparent quantum efficiency of 13.4% at a wavelength of 420 nm due to the synergetic enhancement of surface reactions and charge separation. The present work provides a promising strategy for developing high-performance 2D heterojunctions for clean energy applications.