Facile Fabrication of N‐Doped K2Nb2O6 Nanocrystals with Defective Pyrochlore Structure for Improved Visible‐Light Photocatalytic Hydrogen Production

Abstract

Semiconductor‐based photocatalytic water splitting is one of the effective ways for future hydrogen (H2) production. However, the wide bandgap of most semiconductors severely limits the solar spectral absorption range, which seriously hinders their practical applications. Herein, porous N‐doped K2Nb2O6 nanocrystals with defective pyrochlore structure are rationally designed to extend the absorption range from ultraviolet to visible region around 550 nm by NH3 heat treatment. The obtained 6N–K2Nb2O6 shows the highest visible‐light activity with an H2 evolution rate of 20.4 μmol h−1 g−1. More detailed exploration demonstrates that NH3 heat treatment can promote the substitutional nitrogen doping in K2Nb2O6 crystals while accompanied by the formation of oxygen vacancies or Nb4+ species. The hybridization of N 2p and O 2p orbitals in the valence band (VB) of the nitrogen‐doped K2Nb2O6 makes the VB maximum move more negatively, whereas the conduction band minimum shifted more positively due to the role of defective Nb4+ species. Such a synergistic effect endows the samples with visible‐light absorption and greatly enhances charge separation and transfer efficiency, resulting in the excellent H2 production performance. This study provides additional insights into the understanding of the effect of nitrogen doping on photocatalysts with excellent visible‐light‐driven photocatalytic activity.