MOFs-derived Multi-heterostructured Composites for Enhanced Photocatalytic Hydrogen Evolution: Deciphering the Roles of Different Components

Abstract

Bimetal-organic-framework (Bi-MOF) NH2-MIL-125(Ti/Cu) derived nanocomposites are systematically investigated to elucidate the role of individual species TiO2, CuxO, and porous carbon matrix in photocatalytic activity. Among the studied samples, the TiO2/CuxO/C nanocomposite derived from heat processing NH2-MIL-125(Ti/Cu) under Ar/H2O vapor demonstrates the highest photocatalytic H2 evolution performance due to the formation of phasejunction between well-crystallized anatase/rutile TiO2 polymorph, the optimized and co-doped nitrogen/carbon in the composites, the formation of p-n heterojunction between the TiO2 and CuxO nanoparticles, as well as their uniform distribution in a hydrophilic porous carbon matrix decorated with N and carboxylic functional groups. These parameters enable the in-situ formed multi-heterostructures in these nanocomposites to not only possess relatively narrower energy band gaps and improved spatial charge separation due to the formed type-II staggered p-n heterojunctions, but also offer multiple pathways for charge diffusion, resulting in lower charge transfer resistance, suppressed bulk charge recombination, and consequently much improved visible-light absorption. Therefore, Bi-MOF NH2-MIL-125(Ti/Cu) derived TiO2/CuxO/C nanocomposite provides easily accessible active sites with excellent photocatalytic H2 evolution activity of 3147 µmol gcat-1 h-1, 99 times higher than bare TiO2. This work provides a simple one-step approach to produce tunable novel nanocomposites for efficient photocatalytic H2 evolution without using expensive noble metal as co-catalysts.