Fabrication of nanoporous Ni and NiO via a dealloying strategy for water oxidation catalysis

Nickel oxides and (oxy)hydroxides are promising replacements for noble-metal-based catalysts owing to their high activity and good long-term stability for the oxygen evolution reaction (OER). Herein, we developed nanoporous Ni by a method of combined rapid solidification and chemical dealloying. Subsequently, nanoporous NiO was obtained via heating treatment, the macropore and skeleton sizes of the NiO originated from Ni10Al90 alloy are 100-300 nm and 80-200 nm, respectively. Benefiting from the multi-stage nanoporous structure and high specific surface area, the nanoporous NiO demonstrates an outstanding OER, reaching 20 mA cm(-2) at an overpotential of 356 mV in 1 M KOH. The corresponding Tafel slope and apparent activation energy are measured to be 76.73 mV dec(-1) and 29.0 kJ mol(-1), respectively. Moreover, kinetic analysis indicates that the NiO catalyst shows pseudocapacitive characteristics, and the improved current is attributed to the high-rate pseudocapacitive behavior that efficiently maintains increased nickel redox cycling to accelerate the reaction rates. After 10 0 0 cycles of voltammetry, the overpotential of the NiO decreases by 22 mV (j = 10 mA cm(-2)), exhibiting excellent stability and durability. (C) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.