Enhancement of the OER Kinetics of the Less-Explored α-MnO Nickel Doping Approaches in Alkaline Medium.

Development of a low-cost transition metal-based catalyst for water splitting is of prime importance for generating green hydrogen on an industrial scale. Recently, various transition metal-based oxides, hydroxides, sulfides, and other chalcogenide-based materials have been synthesized for developing a suitable anode material for the oxygen evolution reaction (OER). Among the various transition metal-based catalysts, their oxides have received much consideration for OER, especially in lower pH condition, and MnO is one of the oxides that have widely been used for the same. The large variation in the structural disorder of MnO and internal resistance at the electrode-electrolyte interfaces have limited its large-scale application. By considering the above limitations of MnO, here in this work, we have designed Ni-doped MnO a simple wet-chemical synthetic route, which has been successfully applied for OER application in 0.1 M KOH solution. Doping of various quantities of Ni into the MnO lattices improved the OER properties, and for achieving 10 mA/cm current density, the Ni-doped MnO containing 0.02 M of Ni ions (coined as MnO-Ni) demands only 445 mV overpotential, whereas the bare MnO required 610 mV overpotential. It has been proposed that the incorporation of nickel ions into the MnO lattices leads to an electron transfer from the Ni ions to Mn, which in turn facilitates the Jahn-Teller distortion in the Mn-O octahedral unit. This electron transfer and the creation of a structural disorder in the Mn sites result in the improvization of the OER properties of the MnO materials.