Interfacial Engineering of Metal-Organic Framework-Based Electrode for High-Performance Smart Glass

Prussian blue (PB), a representative metal–organic framework, holds great promise as an electrode material for optical applications. However, the preparation of cycle-stable PB with minimal defects/vacancies and coordinated water has been limited by the uncontrollable growth kinetics. Here, we report on the electrodeposition of a cycle-stable PB film via presilanization on the growth substrate. By self-assembling an aminosilane layer on the indium–tin oxide (a-ITO) substrate before the PB growth, we demonstrate an a-ITO/PB film with minimal defects/vacancies and water (∼5%), as validated by a combination of X-ray photoelectron spectroscopy (XPS), Raman and thermogravimetric analysis (TGA) studies. In addition, scanning electron microscopy (SEM) measurements indicate that the conventional delamination and cracking issue of the PB film can be effectively impeded in our a-ITO/PB film over 1000 cycles. The cyclic tests also indicate that the a-ITO/PB film attains a remarkably higher charge density of 17.4 mC/cm 2 with better stability (charge density retention ∼87% over 1000 cycles) than the state-of-the-art PB benchmark. The crucial role of the aminosilane treatment in increasing the a-ITO/PB interaction/binding is elucidated by density functional theory (DFT) simulations. DFT results suggest that there is a substantial charge redistribution localized around the interface of a-ITO/PB, leading to six times increment in binding energy as compared to non-treated ITO/PB. As an exemplified application, the cycle-stable a-ITO/PB film is applied as an efficient counter electrode in a smart glass. This study paves an effective interfacial engineering means for increasing the binding at the PB–substrate interface and structural integrity of PB itself for long-term electrochemical and optical applications.