Hydrogen evolution and CO2-reduction on a non-supported polypyrrole electrode

Conducting polymers are deposited mostly on a supporting metal of the Pt group and can be used as electrocatalysts. In the present work, a non-supported (bulk) polypyrrole (PPy) is prepared to eliminate any effect of the supporting metal on the desired reactions and is used for the hydrogen evolution reaction (HER) as well as for CO 2 reduction in protic methanol for the first time. The physical, chemical, and electrochemical properties of the synthesized materials are studied in the first step. Scanning electron microscope images reveal that PPy particle size had a change in the range of 30–90 nm (conductivity: 6.2 ×10 −2 ± 0.004 S/cm; four-probe). Tafel slope (82 mV/dec) and activation energy (41.67 kJ/mol) are calculated for HER using cyclic voltammograms. In the second step, the synthesized materials are used for the hydrogenation of CO 2 in acidic methanol. The novel material reduces CO 2 specifically to formic acid at −0.55 V with a maximum Faradaic efficiency of 92 %. • Polypyrrole was prepared chemically as electrocatalysts without any supporting material. • The non-supported polypyrrole electrode has a porous structure and high conductivity. • The non-supported polypyrrole electrode presents an excellent activity for the reduction of CO 2 • HER and CO 2 -reduction were studied on a non-supported polypyrrole electrode for the first time.