Structure and Catalysis of NiOOH: Recent Advances on Atomic Simulation

NiOOH is one of the most promising catalysts for electrooxidation of water and organic molecules. Accompanying the long experimental practice to optimize the catalyst, atomic simulations, mainly based on density functional theory (DFT) calculations, have been performed in recent years to reveal the atomic structure of NiOOH and the reaction mechanism in catalysis. Due to both the structural complexity and the difficulty in computing the electronic structure, there are great concerns over the accuracy of first-principles methods and the validity of the structure models. This Perspective serves to overview the current status of atomic simulation on the structure and catalysis of NiOOH. We first present NiOOH phases and structures obtained by the latest global optimization methods in combination with machine learning potentials. The electronic structures of NiOOH are then described by comparing the performance of different theoretical levels, in particular, those based on PBE+U and hybrid functionals in DFT calculations. Finally, taking the oxygen evolution reaction of water splitting as the example, we elaborate the catalytic mechanism on pure, defective, and Fe-doped NiOOH surfaces and provide insights into the exceptional activity of the doped system. The further directions for theoretical investigations on NiOOH are also discussed.