Oxygen Vacancy and Heterojunction Enhanced 2d Black Nio/1d CDS Visible-Light-Driven Photocatalytic H2 Production Performance and Mechanism Insight

Abstract

Constructing highly active and stable earth-abundant heterojunction to replace expensive and rare metals is regarded as an effective strategy in the photocatalytic H 2  production system. Herein, a NiO with oxygen vacancies and broad absorption in the visible light band is prepared. The introduction of oxygen vacancies leads to the enhancement of catalytic activity and electrical conductivity of NiO.  The hydrogen production efficiency of the product calcined in Ar flow is much higher than that of the product calcined in the air due to the deactivation of surface components and change of morphology active components in the air atmosphere at high temperature. The best NiO/CdS catalyst calcined in Ar flow shows a dramatic Hydrogen evolution rate of 15.6 mmol·g -1 ·h -1  under visible light irradiation, which is comparable to CdS with photo-deposited palladium. The electrons and holes transfer pathway between the CdS and NiO was further investigated by CPD and  in-situ  KPFM technology, after contact with NiO and under illumination, electrons from CdS flow to NiO 1-x  with a higher work function, which enhances absorption of water molecules and accelerates Hydrogen desorption on the surface of NiO, resulting in efficient photogenerated electrons utilization and dramatical Hydrogen production rate.

Keywords: CdS, NiO, oxygen vacancy, in situ KPFM, photocatalytic hydrogen production