The tris(2-pyridyl)phosphine oxide (Py3PO) complex [Ru(Py3PO)(bpy)(OH2)] 2+ (bpy is 2,20-bipyridine) is a pH-dependent water oxidation electrocatalyst that accelerates dramatically with increasing pH—up to 780 s 1 at pH 10 ( 1 V overpotential). Despite retaining the pentakis(pyridine) ligand arrangement common to previously reported catalysts, the tripodal Py3PO ligand framework supports much f...