In-situ synthesis of dual Z-scheme heterojunctions of cuprous oxide/layered double hydroxides/nitrogen-rich graphitic carbon nitride for photocatalytic sterilization

Two-dimensional (2D) layered double hydroxides (LDHs) and graphitic carbon nitride (g-C3N4) with sufficiently positive valence bands and negative conduction bands are promising materials for producing superoxide radicals (·O2-) and hydroxyl radicals (·OH) for photocatalytic sterilization; however, their relatively wide bandgaps limit the utilization of light in photocatalysis. Herein, the electronegative N-CN nanosheets were used to adsorb Cu2+, Zn2+ and Al3+ cations in situ to form uniformly distributed LDHs nanosheets. Then, the LDHs on LDHs/N-CN composites were partially reduced in situ into ultrafine Cu2O to harvest sufficient solar energy. Zeta potential measurements revealed that the constructed Cu2O/LDHs/N-CN composites and bacterial solution exhibited opposite charges, which induced strong electrostatic adsorption in photocatalytic sterilization. Under visible light, the highly hydrophilic 0D/2D/2D Cu2O/LDHs/N-CN heterojunctions exhibited the highest sterilization rate of 98.96% toward Escherichia coli without an obvious decrease after 4 cycles. It was experimentally and theoretically confirmed that a dual Z-scheme charge migration path in the Cu2O/LDHs/N-CN heterojunction was achieved, harnessing the full synergetic potential of the combined system. This work provides an effective method for synthesizing a robust, hydrophilic and positively charged heterojunction to further improve photocatalytic sterilization activity.