Converging Hydrogen-Bonded Water Transport Channel with External Magnetic Field in a Janus Molecular Cobalt Phosphate for Enhanced Oxygen Evolution Reaction (OER) Activity

Increasing the water content and the hydrophobic accessibility through hydrogen-bonded dimeric cavities of Janus-faced mononuclear Co(II) phosphates, pristine complex [Co(Cl-tpy)(dtbppH)2(H2O)]·(H2O)(2MeOH) (1-xtal), and sonicated [Co(Cl-tpy)(dtbppH)2(H2O)]·(H2O)n (1-soni) produces systematic increments in the anodic water-splitting reaction (OER), which is further enhanced by an external magnetic field (50–300 mT), with water-rich 1-soni exhibiting the best electrocatalytic activity and energy efficiency. Such enhanced catalytic activity is traced to spin-state switching of a key intermediate formed during the catalytic cycle, offering a lower kinetic barrier from denisty functional theory calculations. Since the energy gap between these spin states is small, this suggests preferential switching of state with a lower kinetic barrier in the presence of a magnetic field, rationalizing the observed behavior.