(706h) Selectivity of Control of Oxygen Reduction Reaction over Mesoporous Transition Metal Oxides Catalysts for Electrified Purification Technologies

Electrification of oxygen-associated reactions is crucial for large-scale electrical energy storage and the development of the green hydrogen economy. The design of oxygen electrocatalysts can help minimize electrical energy losses and improve control over the reaction products. This study investigates the impact of the interface composition of electrocatalysts on the efficiency and productivity of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), examining both mechanistic aspects and device-level performance.^[1]

Mesoporous nickel (II) oxide and nickel cobaltite (NiO and NiCo₂O₄ ) catalysts, synthesized through a simple template-free hydrothermal method, was employed as ORR and OER catalysts. Physicochemical characterization revealed that both NiO and NiCo₂O₄ are mesoporous, cubic crystal structure, with abundant surface hydroxyl species. Electrochemical tests showed that NiCo₂O₄ demonstrates higher electrocatalytic activity in OER and greater selectivity towards water as the primary product of ORR. Conversely, ORR over NiO leads to the formation of hydroxyl radicals, resulting from a Fenton-like reaction of H₂O₂. The product selectivity in ORR is used to construct two electrolyzers of electrified purification of oxygen and generation of hydroxyl radicals. The optimization of configuration of hydroxyl radical generator enables the degradation of RhB up to 90% after 1 hour, and the electrochemical oxygen purifier shows high efficiency of close to 100%.

The distinct selectivity of ORR products was harnessed to construct electrolyzers for specific applications: oxygen purification and hydroxyl radical generation. This research highlights the potential of tailoring electrocatalysts for selective oxygen electrochemistry, which is relevant to energy storage, green chemistry, and environmental purification.

1. Wu, Z.; Vagin, M.; Boyd, R.; Ding, P.; Pshyk, O.; Greczynski, G.; Odén, M.; Bjork, E. M. Selectivity Control of Oxygen Reduction Reaction over Mesoporous Transition Metal Oxide Catalysts for Electrified Purification Technologies. ACS Appl. Mater. Interfaces 2023, 15 (21), 26093−26103.