Harnessing the Cobalt-Catalyzed Hydrogen Evolution Reaction through a Data-Driven Approach

The design of cobalt complexes for the hydrogen evolution reaction (HER) has garnered significant attention over the past few decades. To address the limitations of the traditional trial-and-error method, we introduced the strategy of a simplified mechanism-based approach with data-driven practice (SMADP) in this study. Our results indicate that the polypyridyl cobalt complexes of the DPA-Bpy family (DPA-Bpy = N,N-bis(2-pyridinylmethyl)-2,2'-bipyridine-6-methanamine) generally follow the electron transfer (E)-chemical proton transfer (C)-electron transfer (E)-chemical proton transfer (C) pathway in HER. However, the involvement of proton-coupled electron transfer (PCET) in the formation of the [Co^II(L)-H]⁺ intermediate has been observed in the PY₅Me₂ family (PY₅Me₂ = 2,6-bis(1,1-di(pyridin-2-yl)ethyl)pyridine). Furthermore, the hydricity of the [Co^II(L)-H]⁺ intermediate (ΔG_H) and the Co^III-H/Co^II-H reduction potential (E_Red^°) are found to be the active descriptors in the cobalt-catalyzed HER. Excellent two-parameter regression models (ΔG_H and E_Red^°) for the formation of the H₂ molecule have been obtained (R² = 0.9429 for the DPA-Bpy family and R² = 0.9854 for the PY₅Me₂ family). Our results demonstrate that the SMADP strategy is a groundbreaking method for delineating active descriptors in the cobalt-catalyzed HER. This data-driven approach could also accelerate the design of novel polypyridyl cobalt complexes for enhanced HER.