Asymmetric charge distribution boosts hydrogen evolution performance in two-dimensional MoO2/MoS2 step heterostructure

Step heterostructures are predicted to hold a profound catalytic performance because of the rearranged electronic structure at their interface. However, limitations in the morphology of heterostructures prepared by hydrothermal reactions or molten salt-assisted strategies make it challenging to directly assess charge distribution and evaluate a single interface's hydrogen evolution reaction (HER) performance. Here, we prepared two-dimensional MoO2/MoS2 step heterostructures with a large specific surface area by the chemical vapor deposition method. Surface Kelvin probe force microscopy and electrical transport measurement verified the asymmetric charge distribution at a single interface. By fabricating a series of micro on-chip electrocatalytic devices, we investigate the HER performance for a single interface and confirm that the interface is essential for superior catalytic performance. We experimentally confirmed that the enhancement of the HER performance of step heterostructure is attributed to the asymmetric charge distribution at the interface. This work lays a foundation for designing highly efficient catalytic systems based on step heterostructures.