The electrochemical CO2 reduction to hydrocarbons and alcohols with sustainable energies is a promising technology for reducing atmospheric CO2 and storing electricity as chemical energy. However, the development of catalysts with high activities, high product selectivities, and low overpotentials to drive the reaction remains a major challenge for practical applications. On Pt, CO2 reduction to CO occurs easily, but further reduction to hydrocarbons and alcohols is difficult because of the strong adsorption of CO on the Pt surface. Consequently, Pt is considered an inactive catalyst and has been studied less than other transition metals such as Cu and Au. Herein, we show that adsorbed CO is selectively reduced to methane on carbon-supported Pt catalysts at low CO2 partial pressures and, crucially, at potentials close to the thermodynamic equilibrium potential of the reaction (0.16 V vs reversible hydrogen electrode), i.e., without overpotentials. Although the estimated apparent faradaic efficiency of 6.8% is not sufficiently high for commercial applications, this is the first demonstration of electrochemical methane generation without an overpotential. We suggest that the overpotential deposition (OPD) of hydrogen atoms at the atop sites of the Pt surface facilitates the reduction of adsorbed CO to methane and that the onset of hydrogen OPD coincidentally matches the equilibrium potential of methane generation. Mechanistic considerations also answer some questions raised by the present experiments, such as why low CO2 pressures are favorable for selective methane generation and why the faradaic efficiency is low. Overall, the results provide useful information for rationally designing effective CO2RR catalysts.

An effective poisoning elimination method for CH4 production from CO2 reduction using a Pt/C electrocatalyst in a polymer electrolyte cell has been established by controlling the Pt–CO/Pt–H ratio and re-arranging the surface adsorption.

We now report the CO 2 -reduction performances of Pt-Ru/C electrocatalysts and power-generation characteristic of a polymer electrolyte fuel cell driven by feeding H 2 and CO 2 to the anode (Pt/C) and cathode (Pt-Ru/C), respectively. The CO 2 electroreduction was evaluated by the current-voltage relationships in combination with in-line mass spectrometry. The onset potentials for the CO 2 reduction are observed at 0.06-0.4 V vs. the reversible hydrogen electrode (RHE), and they depend on the Pt:Ru composition of the Pt-Ru/C cathode. Mass spectrometry revealed that a Pt-rich catalyst generates CH 4 , whereas this gas is not or slightly generated at a Ru-rich catalyst. Based on these results, two significant effects of a small amount of Ru doping to Pt were elucidated: (i) it allows H, which is used for H 2 evolution at the Pt/C, to be used for the CH 4 generation, and (ii) it decreases the adsorption energy of the CO 2 -reduced intermediate (CO) on the Pt. In the fuel cell test, the fuel cell effectively generates power by combining a Pt/C anode and a Pt 0.8 Ru 0.2 /C cathode rather than a Pt/C cathode. Consequently, we demonstrated that Pt 0.8 Ru 0.2 /C exhibits greater performances than Pt/C for the CO 2 reduction and power generation of the H 2 -CO 2 fuel cell.

Generating electric power using CO2 as a reactant is challenging because the electroreduction of CO2 usually requires a large overpotential. Herein, we report the design and development of a polymer electrolyte fuel cell driven by feeding H2 and CO2 to the anode (Pt/C) and cathode (Pt0.8Ru0.2/C), respectively, based on their theoretical electrode potentials. Pt–Ru/C is a promising electrocatalysts for CO2 reduction at a low overpotential; consequently, CH4 is continuously produced through CO2 reduction with an enhanced faradaic efficiency (18.2%) and without an overpotential (at 0.20 V vs. RHE) was achieved when dilute CO2 is fed at a cell temperature of 40 °C. Significantly, the cell generated electric power (0.14 mW cm−2) while simultaneously yielding CH4 at 86.3 μmol g−1 h−1. These results show that a H2-CO2 fuel cell is a promising technology for promoting the carbon capture and utilization (CCU) strategy.

Generating electric power using CO2 as a reactant is challenging because the electroreduction of CO2 usually requires a large overpotential. Herein, we report the design and development of a polymer electrolyte fuel cell driven by feeding H2 and CO2 to the anode (Pt/C) and cathode (Pt0.8Ru0.2/C), respectively, based on their theoretical electrode potentials. Pt-Ru/C is a promising electrocatalysts for CO2 reduction at a low overpotential; consequently, CH4 is continuously produced through CO2 reduction with an enhanced faradaic efficiency (18.2%) and without an overpotential (at 0.20 V vs. RHE) was achieved when dilute CO2 is fed at a cell temperature of 40 °C. Significantly, the cell generated electric power (0.14 mW·cm− 2) while simultaneously yielding CH4 at 86.3 µmol·g− 1·min− 1. These results show that a H2-CO2 fuel cell is a promising technology for promoting the carbon capture and utilization (CCU) strategy.

To identify an electrocatalyst that can effectively generate power and reduce CO 2 , we measured the power generation characteristics of a polymer electrolyte fuel cell fed with H 2 and CO 2 to the anode (Pt/C) and cathode (Pt (1−x) Ru x /C), respectively. The obtained power generation characteristics were compared to their corresponding CO 2 reduction characteristics. A trade-off relationship between the CO 2 reduction and power generation performances was observed. Overall, the Pt 0.8 Ru 0.2 /C electrocatalyst has the potential to be an efficient cathodic catalyst in a H 2-CO 2 fuel cell that reduces CO 2 while generating power.