Hierarchical ZnO/MXene (Nb2C and V2C) heterostructure with efficient electron transfer for enhanced photocatalytic activity

Recently, MXene has attracted much attention as photocatalysts for efficient pollutant degradation in the field of environmental remediation but a rapid recombination of photogenerated carriers usually leads to a decrease in the photocatalytic performance. Constructing a heterostructure is considered as an effective way to improve the catalytic performance of MXene-based photocatalysts due to the promoted interfacial electron transfer. In this work, the chimeric ZnO nanosheets with good carrier mobility were formed on the accordion-shaped MXene (Nb2C and V2C) surface to construct hierarchical ZnO/MXene heterostructure as a photocatalyst for dye degradation. The obtained ZnO/Nb2C and ZnO/V2C hierarchical structure exhibited excellent photocatalytic performance in the degradation of methylene blue (MB): the degradation rate reached 62.62% and 99.53%, respectively, after irradiation with ultraviolet light for 120 min. Also, the apparent degradation rate constants (k) were 0.00777 min−1 and 0.04317 min−1, respectively, which were 2.92 and 16.23 times higher than those of pure ZnO. This was probably attributed to the heterostructures between ZnO and MXene which could shorten the carrier transfer path, which could facilitate the transfer of photo-generated electrons from conduction band (CB) of ZnO to CB of MXene, thereby significantly improving the photocatalytic degradation efficiency. In addition, the ZnO/Nb2C and ZnO/V2C hierarchical structure showed good photocatalytic stability: the degradation rate remained at 58.6% and 97.3%, respectively, after 4 cycles while it only maintained at 22.0% for pure ZnO because the obtained ZnO/MXene hierarchical structure could provide uniform active sites on the surface and porous structure, preventing the aggregation of ZnO or MXene. Therefore, this work could provide a feasible design strategy to improve the catalytic performance of 2D photocatalysts and shed a light on the design of other photocatalysts.