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The increase in the fraction of high-valent metal cations is of significant importance for enhancing the stability of noble-metal-free catalysts in the acid oxygen evolution reaction (OER). Herein, we report the preparation of a cobalt-manganese oxide spinel nanowire catalyst, where the incorporation and stabilization of high-valent cation fractions are induced by electron-withdrawing anionic fluorine groups. By the XPS, the strongly electronegative F atoms improve the ratio of Co3+/Co2+ and Mn4+/Mn3+, thereby enhancing OER activity and stability. The hydrophilicity F-MCO nanowires have a large specific surface area and great conductivity, which expose more catalytically active sites and continuously promotes oxygen evolution. The proposed F-MCO catalyst requires only an overpotential of 210 mV at the current density of 10 mA cm−2 and can maintain stable operation for more than 100 h. And a photovoltaic-electrolysis device with the F-MCO electrocatalyst delivers a solar-to-hydrogen efficiency of 15.1 %. • Rational design of noble metal-free cobalt-manganese spinel nanowire catalyst induced by F atom for enhanced electrocatalytic oxygen evolution from water splitting. • This method significantly enhances the stability of highly valent Co and Mn. • The photovoltaic-electrolysis device with the F-MCO electrocatalyst delivers a solar-to-hydrogen efficiency of 15.1 %. [ABSTRACT FROM AUTHOR]

Phosphorus dopants and defects were successfully introduced to a manganese‐cobalt oxide (MCO) spinel via plasma treatment in the presence of NaH2PO2. High‐energy electrons generated by plasma can produce oxygen vacancy and embed phosphorus into the spinel. To balance the charge of lattice phosphorus, manganese and cobalt atoms left their original sites and deposited as MnO and CoP, thereby forming a disordered structure. Meanwhile, the oxidation state of cobalt increased. These changes provided extra active sites for electrochemical reaction and improved electrical conductivity. In addition, tunnels were formed on the surface, thus favoring mass transport in the electrolyte. Compared with pristine MCO, the spinel doped with phosphorus via plasma treatment showed higher oxygen evolution reaction performance, with a lower onset potential of 1.45 V, higher current density of 25.32 mA cm−2 at 1.75 V, and smaller Tafel slope of 118.7 mV dec−1. These findings can facilitate the development of high‐activity electrocatalysts with dopants and defects for energy storage and conversion systems. [ABSTRACT FROM AUTHOR]

This paper seeks to examine how the Mn–Co spinel interconnect coating microstructure can influence Cr contamination in an oxygen electrode of intermediate temperature solid oxide cells, at an operating temperature of 750 °C. A Mn–Co spinel coating is processed on Crofer 22 APU substrates by electrophoretic deposition, and subsequently sintered, following both the one-step and two-step sintering, in order to obtain significantly different densification levels. The electrochemical characterization is performed on anode-supported cells with an LSCF cathode. The cells were aged prior to the electrochemical characterization in contact with the spinel-coated Crofer 22 APU at 750 °C for 250 h. Current–voltage and impedance spectra of the cells were measured after the exposure with the interconnect. Post-mortem analysis of the interconnect and the cell was carried out, in order to assess the Cr retention capability of coatings with different microstructures.

This paper seeks to examine how the Mn–Co spinel interconnect coating microstructure can influence Cr contamination in an oxygen electrode of intermediate temperature solid oxide cells, at an operating temperature of 750 °C. A Mn–Co spinel coating is processed on Crofer 22 APU substrates by electrophoretic deposition, and subsequently sintered, following both the one-step and two-step sintering, in order to obtain significantly different densification levels. The electrochemical characterization is performed on anode-supported cells with an LSCF cathode. The cells were aged prior to the electrochemical characterization in contact with the spinel-coated Crofer 22 APU at 750 °C for 250 h. Current–voltage and impedance spectra of the cells were measured after the exposure with the interconnect. Post-mortem analysis of the interconnect and the cell was carried out, in order to assess the Cr retention capability of coatings with different microstructures. [ABSTRACT FROM AUTHOR]