Effective alkaline water electrolysis on nwMnO2-nsNi(OH)2 composite electrode via lattice oxygen participant adsorbate evolving mechanism

Highlights: • The MnO₂ nanowires were wrapped by the Ni(OH)₂ nanosheets in the MnO₂-Ni(OH)₂ composites. • 1.0 nwMnO₂-1.0 @CP electrode showed cell voltage of 1.64 V and a low Tafel slope of 68 mV dec⁻¹. • Faradaic efficiency of 96.2% kept on for 300 h. • The synergy between nwMnO₂ and nsNi(OH)₂ accompanies a lattice oxygen participant adsorbate evolving mechanism. To improve and maintain the oxygen evolution reaction (OER) performance of MnO₂ in water electrolysis for a long time, this study attempts to utilize Ni(OH)₂ nanosheets (ns), which have excellent electrochemical properties. Nanocomposites of MnO₂ and Ni(OH)₂ were directly grown on a carbon paper (CP) electrode using hydrothermal synthesis. The MnO₂ nanowires (nw) appeared to be wrapped by the Ni(OH)₂ nanosheets in the MnO₂-Ni(OH)₂ composites. The MnO₂-Ni(OH)₂ composite electrode exhibited better OER performance than the nwMnO₂@CP or nsNi(OH)₂@CP electrodes. In particular, in a 1.0 M KOH alkaline electrolyte, the 1.0 nwMnO₂-1.0 nsNi(OH)₂@CP electrode showed the highest OER performance with a cell potential of 1.64 V and Tafel slope of 68 mV dec⁻¹ at a 10 mA cm⁻² of current density (η = 0.41 V). The X-ray photoelectron spectroscopy of nwMnO₂-nsNi(OH)₂@CP before and after the OER revealed the formation of more oxygen vacancies, which served as OH-adsorption sites, leading to higher OER activity. The stability of the 1.0 nwMnO₂-1.0 nsNi(OH)₂@CP electrode was demonstrated through 300 h-OER long-term tests, which yielded a high Faradaic efficiency of 96.2%. The lattice oxygen transfer plays a significant role in enhancing the intrinsic activity of catalysts during OER. The synergy between nwMnO₂ and nsNi(OH)₂ accompanies a lattice oxygen participant adsorbate evolving mechanism.