Li-based batteries are currently the most widely used energy storage technology in electric vehicles and portable electronic devices, but discarded batteries represent a growing environmental hazard. The flammability of the liquid electrolyte particularly requires exploration of alternative recycling methods. Herein, we report the photochemical conversion of usual carbonate-based electrolytes into a new catalyst with remarkable activity and selectivity for the CO2 reduction reaction. Solutions of LiPF6 in different organic solvents are first deposited on a Cu substrate and irradiated by a 1.88 eV laser. After air exposure, a layer consisting of LiF and graphitic carbon deposited on CuxO is obtained. When tested for the electrochemical reduction of CO2, this material converts in situ into an effective catalyst with a faradic efficiency as high as 46.7% for CH4, which is maintained above 40% for at least 100 h.