Facile synthesis of multi-layer Co(OH)2/CeO2-g-C3N4 ternary synergistic heterostructure for efficient photocatalytic oxidation of NO under visible light
Zhiyu Xiao, Hainam Do, Abubakar Yusuf, Hongpeng Jia, Haolun Ma, Shanshan Jiang, Jian‐Rong Li, Yong Sun, Chengjun Wang, Yong Ren, George Z. Chen, Jun He
Abstract
In this work, we report a one-step synthesis of ternary Z-scheme Co(OH)2/CeO2-g-C3N4 (CoCe-CN) heterostructure via hydrothermal method. Owing to the modification of Co(OH)2 and CeO2, the existence of Co(OH)2 as an electron acceptor-donor center between CeO2 and g-C3N4 accelerates the electron transfer and provides extra OH- reaction pathway for photocatalytic oxidation of NO. As a result, 50CoCe-CN (Co and Ce accounting for 25% mass ratio separately) achieved a 53.5% conversion efficiency of NO at 600 ppb concentration, which is 1.82 times that of g-C3N4 under visible light. The results of the DFT analysis and element distribution of cobalt and ceria provide convincing evidence supporting the existence of a novel multi-layer structure in the CoCe-CN photocatalyst. This structure involves the loading of CeO2 and Co(OH)2 on the g-C3N4 surface, and Co(OH)2 as a co-catalyst introduced between CeO2 and g-C3N4 realizes the synergy between CeO2 and Co(OH)2 which further improve the photocatalytic properties. The higher photocatalytic efficiencies observed in the CoCe-CN photocatalysts compared to those containing only cobalt (Co-CN) or ceria (Ce-CN) provide further evidence of the synergistic effect of these two elements. This work demonstrates a more efficient and effective ternary photocatalytic system, with greater practical potential for photocatalytic oxidation of NO. NOx is considered as a harmful air pollutant in both outdoor and indoor environments， which can lead to photochemical smog and cause respiratory diseases via the exposure. Herein, a ternary heterostructure Co(OH)2/CeO2-g-C3N4 photocatalyst was fabricated using a facile ultrasonication-hydrothermal process which was found to improve the oxidation efficiency up to 53% at the NO concentration down to ppb level. In this photocatalyst of multi-layer structure, Co(OH)2 not only promotes the electronic communication between g-C3N4 and CeO2, but also provides an efficient pathway to utilize OH- to accelerate the production of •O2- and •OH.