Highly active nickel oxide water oxidation catalysts deposited from molecular complexes

Nickel oxide (NiOx) water oxidation catalysts with high catalytic activity have been electrodeposited from [Ni(en)(3)]Cl-2 (en = 1,2-diaminoethane, NiOx-en) in a 0.10 M borate buffer (NaBi) solution (pH = 9.2). Electrolysis experiments at a fixed applied potential of 1.1 V (vs. Ag/AgCl) established that the NiOx-en films sustain a stable current of 1.8 mA cm(-2) for extended periods, compared with 1.2 mA cm(-2) for films derived from [Ni(OH2)(6)](NO3)(2) and [Ni(NH3)(6)]Cl-2 when tested in a 0.60 M NaBi buffer. XAS studies indicate that the gamma-NiOOH phase is formed in each case whereas SEM studies revealed significant differences in film morphology. The NiOx-en films were found to be more homogenous and to have a higher electroactive surface area, as determined from capacitance measurements. The results highlight the influence that the choice of molecular precursor can have on the activity and robustness of electrodeposited NiOx water oxidation catalysts.