Abstract
The hydrogen evolution reaction (HER) is central to green hydrogen production, yet 2D electrocatalysts are limited by inert basal planes, low densities of well-defined edges, charge-transfer barriers, and single-site scaling. In this talk, we present high-quality CVD-grown 2D materials and three atomic-engineering strategies for MoS₂-based catalysts: nanoribbon edge engineering, multisite cooperation, and Janus symmetry breaking. First, templated subtractive patterning produces large-area arrays of crystalline, sub-30-nm MoS₂ nanoribbons with a high density of well-defined, primarily zigzag edges. Their geometry reduces basal-to-edge charge-transfer barriers, yielding edge-dominated HER kinetics with an approximately 200-fold increase in turnover frequency. Second, multisite catalysts can overcome single-site scaling by separating adsorption and desorption across distinct active sites, yet their precise fabrication and experimental validation remain challenging. We realize and validate multisite electrocatalysis using van der Waals-stacked WS₂/MoS₂ edges with atomically controlled site separation. Intermediate exchange enables HER beyond single-site Sabatier scaling, whereas altering the separation restores single-site behavior, as demonstrated by electrostatic control and supported by ab initio calculations. Bifunctional edge assemblies further enable efficient neutral overall water splitting. We are extending this strategy to the one-step growth of vertically stacked heterostructure catalysts. Finally, uniform conversion of monolayer MoS₂ into Janus MoSSe breaks out-of-plane symmetry and activates both basal-plane and edge sites. The MoSSe basal plane outperforms the basal planes of MoS₂ and MoSe₂, while its edge shows even greater HER enhancement, with a 32-fold higher exchange current density than the MoS₂ edge. This enhancement is consistent with a previously predicted Se-assisted hydrogen-transfer pathway. Repeated HER cycling further activates the edge, suggesting reaction-induced self-optimization. Together, these findings demonstrate the potential of atomic engineering to overcome intrinsic limitations in 2D electrocatalysis and advance efficient hydrogen evolution and overall water splitting.
References
- D.-R. Chen, J. Muthu, X.-Y. Guo, H.-T. Chin, Y.-C. Lin, G. Haider, C.-C. Ting, M. Kalbáč, M. Hofmann, and Y.-P. Hsieh, Journal of Materials Chemistry A, 11 (2023) 15802–15810.
- H. Wang, D.-R. Chen, Y.-C. Lin, P.-H. Lin, J.-T. Chang, J. Muthu, M. Hofmann, and Y.-P. Hsieh, ACS Nano, 18 (2024) 19828–19835.
- D.-R. Chen, J. Muthu, J.-T. Chang, P.-H. Lin, Y.-X. Chen, F. Khurshid, H.-T. Chin, J. Kong, M. Hofmann, and Y.-P. Hsieh, Nano Letters, 25 (2025) 12059–12066.