From one to three: how to achieve well-steered spatial charge separation in Janus-like asymmetrically graphene oxide films for high photocatalytic performance

Generally, Janus materials that include different functional compartments on their opposite faces offer great advantages for spatial charge separation in a heterojunction system. Here we demonstrate a general preparation strategy of Janus-like CdS/MnS graphene oxide films (CdS/JGFs/MnS) with a novel asymmetric structure along with the different faces of the films by interfacial reaction, where CdS and MnS nanoparticles (NPs) are in situ deposited on opposite faces of graphene oxide films, respectively. Such an asymmetric Janus p-n heterostructure can be conductive to light absorption and provide an intimate heterojunction interface between photocatalysts, which can facilitate photoexcited electron-holes near the Janus GO surface to transfer in the opposite direction to improve catalytic activity. Compared with their mixed counterparts, the Janus photocatalysts exhibit a much higher photocatalytic performance due to better steered charge-carrier separation. With this special configuration, the unique Janus p-n heterojunction displays an ultrahigh photodegradation (towards methyl orange (MO) about 86% within 25 min) and disinfection (approximately 6.7 log Escherichia coli (E. coli) inactivation) efficiencies and high cyclic stability. The general nature of the preparation protocols of Janus graphene oxide films provides a universal strategy for spatial charge separation and other potential applications.