Facile synthesis of electrocatalytically active Cu/graphite using the negative electrode of spent Li-ion batteries

Abstract

We demonstrate that graphite-powder-supported Cu-based fine particles, which exhibit unique electrocatalytic performance, are facilely producible at room temperature using the graphite negative electrode of a spent Li-ion battery. A majority of impurity substances containing Li, F, and P, which are the elements attributable to the solid electrolyte interphase formed on the surface of spent graphite powder, were removed by washing with water. By contrast, when the spent graphite was dispersed into a CuCl₂ aqueous solution, P remained along with deposited Cu species, whereas Li and F were similarly removed. Synchrotron and microstructural analyses revealed that the fine particles deposited onto graphite powder were mainly composed of copper oxides such as Cu₃(PO₄)₂ and CuO, which were subsequently reduced by an electrochemical treatment at room temperature, resulting in metallic Cu particles with a needle-like morphology. The thus-obtained Cu/graphite powder was found to be active toward the electrochemical synthesis of C₂₊ products (i.e., C₂H₄, C₂H₅OH and C₃H₇OH). The results also showed that such catalytically active Cu-based compounds were not formed on graphite in the case where a pristine graphite powder was used, suggesting that the use of a spent graphite negative electrode would open an environmentally benign route to the synthesis of electrocatalysts.