Nickel Selenide As High-Efficiency Catalyst for Oxygen Evolution Reaction

Electrolytic water splitting is considered to be clean energy generation and a substitute for fossil fuels and oxygen evolution reaction (OER) is an important reaction involved in water splitting. However, OER typically being a 4 electron process requiring O – O bond formation is a kinetically slow process typically requiring catalysts. 1 Identifying more-efficient, stable, earth-abundant catalysts for the OER has long been researched. Recently, Ni-oxide based OER electrocatalysts were found to exhibit high efficiency, and it was stated that the catalytic performance can be further tuned by increasing covalency in the metal-oxygen bonds. The catalytic properties of the metal oxides can also be influenced through other variables of the electrodeposition reaction such as the total and relative concentration(s) and composition(s) of dissolved metal salts and extra electrolytes, the pH, and the duration of the electrodeposition current. 2 Here we report, for the first time, a metal-rich form of Ni-selenide, Nickel subselenide, Ni 3 Se 2 as a potential oxygen evolution electrocatalyst in alkaline condition. The Ni 3 Se 2 phase has a structure similar to the sulfur mineral Heazlewoodite , which contains metal – metal bonding. The electrocatalytic activities of Ni 3 Se 2 towards OER was seen to be at par with or even superior to the transition metal oxide based electrocatalyst in terms of onset overpotential for O 2 evolution as well as overpotential to reach a current density of 10 mA/cm 2 (observed at 290 mV). The electrocatalytic Ni 3 Se 2 were grown by electrodeposition on conducting substrates and the deposition parameters including pH of the electrolytic bath, deposition potential, and substrate composition were seen to have some influence on the catalytic activity. Annealing of the as-deposited electrocatalytic films in an inert atmosphere enhanced their catalytic efficiencies by decreasing the overpotential (@10 mA/cm 2 ) as well increasing the current density. In addition to low overpotentials, these Ni 3 Se 2 electrodeposited films were seen to be exceptionally stable under conditions of continuous O 2 evolution for extended period (48 – 66 h). The structure and morphology of these films has been characterized with powder X-ray diffraction, Scanning and Transmission electron microscopy, Raman, and X-ray photoelectron spectroscopy. We will discuss in detail the electrochemical and structural characterizations of these films along with catalytic activities. References: 1. E. Mirzakulova, R. Khatmullin, J. Walpita, T. Corrigan, N. M. Vargas-Barbosa, S. Vyas, S. Oottikkal, S. F. Manzer, C. M. Hadad, and K. D. Glusac, Nature Chem . 2012, 4, 794. 2 McCrory, C. C. L.; Jung, S. H.; Peters, J. C.; Jaramillo, T. F. J. Am. Chem. Soc . 2013, 135, 16977.