Synthesis of MnNiO3/Mn3O4 nanocomposites for the water electrolysis process.

The hydrothermal method was optimized to produce highly efficient, novel MnNiO₃/Mn₃O₄ nanocomposites for water electrolysis. The predominant peak observed at 36.6° corresponds to the X-ray crystal plane orientation of (1−10) and confirmed rhombohedral phase MnNiO₃. The other well-resolved peaks were attributed to MnNiO₃/Mn₃O₄ nanocomposites. Vibrational properties and metal oxygen vibrations were revealed in Fourier transform infrared profile around ~570–620 cm⁻¹. The oxygen vacancies and electron trapping mechanism were exposed from photoluminescence spectra. The combined morphology of nanorods and distinguished nanopetals was determined for highly active MnNiO₃ nanocatalyst. The band structure and modification was thoroughly studied by employing UV-visible diffuse reflection spectra and the observed band gap was 2.8 eV for MnNiO₃/Mn₃O₄ nanocomposites. Cyclic voltammogram and linear sweep voltammogram study were used to investigate the redox behavior and water oxidation nature of the novel MnNiO₃/Mn₃O₄ nanocomposites. A higher OER activity of 274 mA/g at 10 mV/s was achieved for the electrode loaded with optimized electrocatalysts. The excellent conductivity and ionic mobility were confirmed by electrochemical impedance spectra. The 72-h stability test was carried out and long-time durability was reported for the optimized electrocatalysts. Thus, the present study completely dealt with the preparation of novel combinations of MnNiO₃/Mn₃O₄ nanocomposites by using controlled synthesis techniques and the exploration of optimized candidates for efficient water electrolysis process. Highlights: New combination of MnNiO₃/Mn₃O₄ nanocomposites for water electrolysis. Higher current density of 274 mA/g was achieved at 10 mV/s. Sixty-seven percent of retention was achieved after 72 h of continuous water electrolysis. [ABSTRACT FROM AUTHOR]