Microwave-assisted synthesis of FeN Co-doped ZIF-8 derived carbon for low-concentration lithium recovery via CDI: Adsorption performance and mechanism

Microwave synthesis enables atomic Fe dispersion in ZIF-8 - derived carbon. • Fe-doped carbon boosts low-concentration Li + adsorption via CDI. • Fe doping tunes porous structure and active sites. • Li + adsorption on Fe-N 4 is clarified by characterization and DFT. Lithium ions are widely present in various water resources, but their extraction has long been constrained by low lithium concentration in various water resources, necessitating the development of efficient extraction technologies. Capacitive deionization (CDI) is an emerging, energy-efficient technology for lithium recovery, yet its efficacy is largely constrained by the limited adsorption capacity of existing electrode materials. Herein, we developed a facile method to fabricate Fe N co-doped porous carbon materials (Fe-NC-M) derived from Zeolitic Imidazolate Framework-8 (ZIF-8) via a microwave-aided pyrolysis route. Microwave-assisted pyrolysis, leveraging rapid volumetric heating and selective energy absorption to achieve uniform Fe N 4 dispersion and construct a hierarchically porous carbon skeleton, effectively suppressing metal agglomeration. By modulating the Fe doping content, the electronic structure and surface chemistry of the carbon skeleton are refined, resulting in a remarkable enhancement in Li + adsorption. The optimized Fe-NC-M-150 electrode demonstrates an appreciable adsorption capacity for lithium ions, measuring 17.34 mg/g, surpassing most reported carbon-based CDI materials. Moreover, the electrode exhibits stable cyclic performance with 84.4% capacity retention after 20 adsorption-desorption cycles. A combination of physicochemical characterization, electrochemical analysis, and Density Functional Theory (DFT) calculations reveals that the Fe N 4 sites improve conductivity and ion diffusion kinetics, and provide strong coordination sites for Li + adsorption. This work provides a feasible strategy for designing high-performance CDI electrode materials toward efficient lithium resource recovery from low-concentration lithium resources. Download: Download high-res image (319KB) Download: Download full-size image