One-Step Synthesis of Nb2 O5 /C/Nb2 C (MXene) Composites and Their Use as Photocatalysts for Hydrogen Evolution.

Hydrogen production through facile photocatalytic water splitting is regarded as a promising strategy to solve global energy problems. Transition-metal carbides (MXenes) have recently drawn attention as potential co-catalyst candidates for photocatalysts. Here, we report niobium pentoxide/carbon/niobium carbide (MXene) hybrid materials (Nb2 O5 /C/Nb2 C) as photocatalysts for hydrogen evolution from water splitting. The Nb2 O5 /C/Nb2 C composites were synthesized by one-step CO2 oxidation of Nb2 CTx . Nb2 O5 grew homogeneously on Nb2 C after mild oxidation, during which some amorphous carbon was also formed. With an optimized oxidation time of 1.0 h, Nb2 O5 /C/Nb2 C showed the highest hydrogen generation rate (7.81 μmol h-1  gcat-1 ), a value that was four times higher than that of pure Nb2 O5 . The enhanced performance of Nb2 O5 /C/Nb2 C was attributed to intimate contact between Nb2 O5 and conductive Nb2 C and the separation of photogenerated charge carriers at the Nb2 O5 /Nb2 C interface; the results presented herein show that transition-metal carbide are promising co-catalysts for photocatalytic hydrogen production.