Spatial distribution of ZnIn2S4 nanosheets on g-C3N4 microtubes promotes photocatalytic CO2 reduction

The graphitic carbon nitride (g-C3N4) is regarded as a powerful support for constructing heterojunction. How to rationally design high-performance g-C3N4-based heterojunction remains a great challenge. In this work, a kind of spatial distribution heterojunction is prepared by in situ growing ZnIn2S4 (ZIS) nanosheets on g-C3N4 microtubes (T-CN). To highlight the advantage of such a structure design, g-C3N4 bulk (B-CN) and g-C3N4 nanosheets (S-CN) are also used as the supports to obtain B-CN/ZIS bulk heterojunction and S-CN/ZIS 2D/2D heterojunction, respectively. T-CN/ZIS spatial distribution heterojunction combines the hierarchical core/shell structure of B-CN/ZIS and ultrathin structure of S-CN/ZIS, which is much favorable for photocatalytic CO2 reduction. It is found that the gas yield from CO2 reduction is highest over T-CN/ZIS, which is 3.5 and 1.5 times higher than B-CN/ZIS and S-CN/ZIS. The experimental results manifest that the spatial distribution of ZIS nanosheets on T-CN induces stronger photoabsorption, faster interfacial charge transfer, and larger CO2 adsorption, all of which are responsible for the best catalytic activity. It is expected that this work will provide an instructive guideline for designing g-C3N4-based heterojunction.