A generalized approach for enhancing contact-electro-catalysis of oxides in a broad temperature range by fluorination

Abstract

Contact-electro-catalysis (CEC) has emerged as a sustainable and effective strategy for promoting chemical reactions. While polymers are the mostly used CEC catalysts, their limited contact-electrification (CE) performance at high temperatures limits the application of CEC in some environment. Here, we engineer fluorinated functional groups onto a series of oxides (SiO2 Al2O3, ZrO2 and MgO) for enhancing their CE abilities. The fluorinated SiO2 (F-SiO2), for example, exhibits comparable CEC efficiency to that of polymers at room temperatures, and, more importantly, superior performance at elevated temperatures up to 180 °C. This should be mainly ascribed to the thermal stability of F-SiO2 and the facilitated electron transfer enabled by fluorinated functional groups. The practicability of F-SiO2 is verified by CEC-leaching of ternary cathodes of spent lithium-ion battery at 70 °C, with leaching efficiencies for all elements exceeding 90% within 300 min. Given the fluorination-based improvement is feasible for various oxides, we expect this strategy could not only enrich the spectrum of effective CEC catalysts, but also render a general approach for more efficient CEC process in a broad temperature window.