Abstract
Coordination complexes are promising candidates for powerful electrocatalytic oxygen evolution reaction (OER) but challenges remain in favoring the kinetics behaviors through local coordination regulation. Herein, by refining the synergy of carboxylate anions and multiconjugated tripodal benzimidazole ligands, we tailor a series of well-defined and stable coordination complexes (CCs), Ni-tPBA0~3, with three-dimensional (3D) supramolecular/coordinated structures. The coordinated water as potential open coordination sites (OCSs) can directly become intermediates, while the metal center easily achieves re-coordination with water molecules in the pores to resist lattice oxygen dissolution. Specifically, nickel centers with mono-coordinated water undergo the intermolecular oxygen coupling while those with neighboring coordinated water molecules follow an intramolecular oxygen coupling mechanism (IOM) with a low thermodynamic energy barrier. With more coordinated water introduced, an optimized IOM process appears with the synergy of potential OCSs, enabling fast generation of –Ni–(OH)x intermediate and synchronizing the re-coordination of water molecules with the deprotonation of active –OH for enhanced kinetics. As such, a low overpotential of 265 mV at 10 mA cm–2 and long-term stability of 150 h at 100 mA cm–2 was achieved, superior to most single transition metal-based molecular electrocatalysts. This study underscores the potential of crafting the coordinated water molecules for efficient electrocatalysis applications.