Investigation into the performance of Ag2O/g-C3N4 p-n heterojunction photocatalysts with efficient H2 production activity

Abstract

The use of photocatalysts to break down water into hydrogen (H2) is one of the effective ways to solve energy scarcity and environmental pollution. The light utilization efficiency and separation efficiency of photogenerated carriers are key parameters for their application in photocatalytic H2 production. In this work, direct Z-scheme p-n heterojunction composites consisting of Ag2O and g-C3N4 (Ag2O/CN) were synthesized via an in-situ synthesis method. Characterizations of the synthesized Ag2O/CN composites were conducted to understand the performance of the photocatalysts for H2 production and to elucidate the possible mechanism. The experimental parameters such as Ag2O loading, sacrificial agent and electrolyte condition on photocatalytic H2 production were also investigated. The results show that the Ag2O/g-C3N4 composites have a favorable photoelectric effect and exhibit better H2 evolution performance than the single Ag2O and g-C3N4. The optimum formulation for the Ag2O/CN composites is to use triethanolamine as the sacrificial agent, 0.1 M KOH as the electrolyte, and 3 wt% Ag2O loading (3Ag2O/CN). The highest H2 production of 3Ag2O/CN is 7966.16 μmol/g/h, which is 3.68 and 195.48 times higher than that of g-C3N4 (2165.18 μmol/g/h) and Ag2O (40.75 μmol/g/h), respectively. The direct Z-scheme p-n heterojunction formed by g-C3N4 and Ag2O is the main reason for the enhanced photocatalytic activity. This study provides new ideas for the design of efficient g-C3N4-based p-n heterojunctions.