Development of effective oxygen evolution reaction (OER) electrocatalysts has been intensively studied to improve water splitting efficiency and cost effectiveness in the last ten years. However, it is a big challenge to obtain highly efficient and durable OER electrocatalysts with overpotentials below 200 mV at 10 mA cm-2 despite the efforts made to date. In this work, the successful synthesis of supersmall α-Ni(OH)2 is reported through electro-oxidation of NiSe2 loaded onto carbon nanoarrays. The obtained α-Ni(OH)2 shows excellent activity and long-term stability for OER, with an overpotential of only 190 mV at the current density of 10 mA cm-2 , which represents a highly efficient OER electrocatalyst. The excellent activity could be ascribed to the large electrochemical surface area provided by the carbon nanoarray, as well as the supersmall size (≈10 nm) of α-Ni(OH)2 which possess a large number of active sites for the reaction. In addition, the phase evolution of α-Ni(OH)2 from NiSe2 during the electro-oxidation process was monitored with in situ X-ray absorption fine structure (XAFS) analysis.
Keywords: Ni (oxy)hydroxide; X-ray absorption spectroscopy; nickel diselenide; oxygen evolution reaction; α-Ni(OH)2.
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