Direct electrification of oxygen-associated reactions
contributes
to large-scale electrical storage and the launch of the green hydrogen
economy. The design of the involved catalysts can mitigate the electrical
energy losses and improve the control of the reaction products. We
evaluate the effect of the interface composition of electrocatalysts
on the efficiency and productivity of the oxygen reduction reaction
(ORR) and oxygen evolution reaction (OER), both mechanistically and
at device levels. The ORR and OER were benchmarked on mesoporous nickel(II)
oxide and nickel cobaltite (NiO and NiCo2O4,
respectively) obtained by a facile template-free hydrothermal synthesis.
Physicochemical characterization showed that both NiO and NiCo2O4are mesoporous and have a cubic crystal structure
with abundant surface hydroxyl species. NiCo2O4showed higher electrocatalytic activity in OER and selectivity to
water as the terminal product of ORR. On the contrary, ORR over NiO
yielded hydroxyl radicals as products of a Fenton-like reaction of
H2O2. The product selectivity in ORR was used
to construct two electrolyzers for electrified purification of oxygen
and generation of hydroxyl radicals.