Robust High-performance Bifunctional Porous Cobalt MOF-Based Catalysts for Overall Water Splitting

MOF-based materials, as bifunctional catalysts for electrocatalytic water splitting, play an important role in the application and development of clean fuel hydrogen energy. This study presents a series of novel 3D Co-based MOFs with layered networks, including [Co(4,4'-bipy)_0.5(aip)(CH₃OH)·H₂O] (Co-MOF 1), [Co₂(1,3'-bit)(aip)₂(CH₃OH)·H₂O] (Co-MOF 2), [Co(4,4'-bipb)(aip)] (Co-MOF 3), and [Co₂(4,4'-bipe)(aip)₂·1.5H₂O] (Co-MOF 4). Their single-crystal structures of Co-MOFs 1-4 are characterized and analyzed before being applied in alkaline solutions for water decomposition (OER and HER). The electrocatalytic tests indicate that Co-MOFs 1-4 exhibit a good performance. Notably, Co-MOF 4 exhibits great behavior which has low overpotentials of 94 and 188 mV (OER) as well as 185 and 352 mV (HER) at the currents of 10 and 100 mA cm^-2, respectively. In comparison with Co-MOFs 1-3, Co-MOF 4 has the lowest Tafel slopes, highest ECSA, and smallest resistance. The immanent qualities, such as distinct interwoven long chain layered structure, unsaturated coordination modes, and synergistic catalytic qualities among Co ions, contribute to explaining the results. The fundamentals provide valuable information for the investigation of innovative MOF-based bifunctional electrocatalysts for overall water splitting.