Solution-Processed Ni-Based Nanocomposite Electrocatalysts: An Approach to Highly Efficient Electrochemical Water Splitting

In this study, we report an up-scalable and low-cost solution-processed method to in situ synthesize an earth-abundant nonstoichiometric NiO x -based electrocatalytic film for water oxidation. The catalytic activity was found to be inversely proportional to the baking temperature, which varied from 50 to 500 C. We found the formation of a hybrid nanocomposite thin film of NiO x nanocrystals (<2 nm size) inside an acetate-based organic matrix at low temperatures (<200 C). The defective and short-range structural order of the NiO x -based nanocomposite electrocatalysts, compatible with lattice stress, low electrical conductivity, and high density of catalytically active surface species, and higher Fe incorporation were responsible for the enhanced electrocatalytic activity. Our champion NiO x catalyst features a 358 mV overpotential at 10 mA cm -2 and more than 60 h of continuous operation without significant losses, which is a remarkable milestone for undoped NiO x electrocatalysts synthesized at nearly room temperature by a solution-processed up-scalable method.