Bimetallic MnNi-hydroxide electrodeposited on Ni-foam for superior water-splitting and energy storage.

Electrochemical energy conversion (via water splitting) and storage (via supercapacitors) are emerging strategies for developing the renewable energy sector; nevertheless, the hunt for low-cost and effective electrode material is a bottleneck issue. Herein, a bimetallic manganese nickel hydroxide was electrodeposited on Ni-foam without polymeric binder, followed by calcination to reveal its oxide configuration. As prepared, manganese nickel hydroxide (MnNi-hydroxide) displayed low Oxygen evolution reaction (OER) and Hydrogen evolution reaction (HER) overpotentials of 231 mV and 327 mV at 10 mA/cm2 during electrochemical water splitting, along with a superior turnover frequency of 0.12 sec−1 and 0.056 sec−1, respectively. Theoretical investigations revealed an increase in MnNi-hydroxide activity due to synergistic electronic interaction between Mn and Ni. Further, the MnNi-hydroxide, having high specific capacitances of 1174 mF/cm2 at 2 mV/s and 308 mF/cm2 at 1 mA/cm2, demonstrated a retention capacity of 98.9% over 5000 cycles. [Display omitted] • A bimetallic Mn-Ni hydroxide was electrodeposited on Ni-foam without polymeric binder. • Mn-Ni hydroxide displayed low OER and HER overpotentials of 231 mV and 327 mV at 10 mA/cm2. • This material also showed high specific capacitances of 1174 mF/cm2 at 2 mV/s and 308 mF/cm2 at 1 mA/cm2. • The synergistic interaction between Mn and Ni is a crucial factor in the efficient bifunctional activity. [ABSTRACT FROM AUTHOR]