Crystal reconstructed cubic nickel oxide with energetic reactive interfaces for exceptional electrochromic smart windows.

Electrochromic smart windows can realize intelligent photothermal regulation by applying a low potential, which is of great significance for energy-saving buildings and achieving low carbon emission. However, the dense structure of conventional metal oxide electrochromic materials limits ion transport efficiency, resulting in poor electrochromic properties. Here, we propose a surface crystal reconstruction strategy for cubic NiO through phosphorylation (P-NiO) to build energetic reactive interfaces and enhance the electrochromic performance. Theoretical simulations and experiments reveal that the introduction of PO tetrahedra tailored the crystal structure of cubic NiO, which endows it with a large number of contiguous intracrystal cavities and unsaturated P-O bonds on the surface. The energetic reactive interface optimizes the transport path of OH and gets rid of the dependence on K in the adsorption process, thus improving the reaction kinetics of NiO. The P-NiO film delivers a large optical modulation (90.3%, at 500 nm), a high coloration efficiency (81.1 cm C, at 500 nm), and a fast switching speed (6 s and 7.2 s for coloring and bleaching processes). Furthermore, a model of an electrochromic smart window was fabricated based on the P-NiO film, using which a potential energy saving of 60.81 MJ m and CO emission reduction of 11.98 kg m can be achieved in hot climate zones according to energy simulations. The in-depth insights gained into the fundamental mechanism of this surface crystal reconstruction strategy will facilitate the rational design of high-performance electrochromic and electrochemical materials.