Temperature-dependent tailoring of the pore structure based on MOF-derived carbon electrodes for electrochemical capacitors

The pore structures of carbon play a critical role in the charge storage process of electrochemical capacitors; however, the involvement of other varying characteristics, such as electrical conductivity and surface functionalities, complicate the research of the pore size effects on various electrochemical phenomena. In this study, by carbonizing MOF-5 at a selected temperature range of 500-700 °C, a series of MOF-derived carbon materials were obtained with pore size distribution concentrated in different size ranges while admitting similar results in the graphitization degree and surface functionalities. The related morphological changes of ZnO were systematically investigated by changing the carbonization temperature and dwelling time, demonstrating a "from thin to thick, from inside to outside" growth routine of ZnO crystals. With the pore size approximated as the sole variable, the as-assembled electrochemical capacitors present a linear relationship between the 1-10 nm pores and the impedance resistance, which for the first time demonstrate how 1-10 nm pores is beneficial to ion diffusion. The results of this study not only provide a useful approach to manipulating the pore structure in carbon electrodes but also pave the way to establish the numerical relationship between the pore structure and various phenomena in electrochemistry or other related areas.