High-pressure synthesis of CO and syngas from CO2 reduction using Ni−N-doped porous carbon electrocatalyst

Abstract

Electrochemical conversion of CO2 to CO or syngas (CO/H2 mixture) is considered one of the most promising approaches to valorise waste-CO2. To develop the process on industrial scale, it would be necessary to use selective and inexpensive electrodes and to obtain high productivities with low energy consumption. In this frame, Ni−NC catalysts are considered among the most interesting ones because of their relatively low cost, high faradaic efficiency in CO (FECO), and high stability. However, up to now, quite low productivities were obtained as a result of low current densities achieved in aqueous electrolytes. In this work, we have evaluated the performances of a Ni−NC electrocatalyst at relatively high carbon dioxide pressures (5–30 bar) in a wide range of cell potentials and current densities. It is found that proper selection of CO2 pressure and catalyst loading improves drastically the performance of the process, obtaining high FECO (close to 100%), high current densities (>100 mA cm−2), and high productivities. Furthermore, it is shown that it is possible to obtain syngas with a target ratio of two between H2 and CO under various operating conditions. As an example, syngas was obtained with FE close to 100% and a productivity of ∼18 mol h−1 m−2 working at 30 bar with a current density close to 195 mA cm−2