Flexible On-Chip Device for In Situ Density of States Measurement and Understanding the d-Band Theory with Experiment

The performance of electrocatalysts is intrinsically related to their density of states (DOS). This relationship is well understood with the d-band center theory, which was first proposed in 1995. The DOS is typically obtained from theoretical calculations in this theory. It would be interesting to measure the DOS and electrocatalytic performance experimentally and explore the regulation between them. A flexible on-chip microdevice has been designed to measure/modulate the DOS and electrocatalysis within the same monolayer MoS 2 flake. It is demonstrated that there is a linear responsiveness of MoS 2 electrocatalytic performance to the defect d-band center, consistent with theoretical predictions. By tuning the defect d-band center, the hydrogen evolution reaction overpotential could be decreased from 199 to 40 mV. This study establishes an experimental validation framework bridging the tested DOS to electrocatalysis, offering a new strategy for designing high-performance electrocatalysts through defect states engineering.