Voltammetric study of one-step electrochemical methane production during water and CO2 co-electrolysis in molten CsH2PO4

Cyclic voltammetry was performed with a nickel electrode in molten CsH2PO4 at 350 °C and at approximately 25 bar of water pressure. The effect of adding carbon dioxide was examined. It is found that even small amounts of CO2 (partial pressure below 0.2 bar at 350 °C, corresponding to 0.5 bar at 22 °C of a 5:1 mixture of N2:CO2) have a pronounced effect on the cyclic voltammetry curves. Under these conditions the hydrogen formation is substituted by another process, methane formation. At the same time the cathodic current increased by a factor of 4–6, meaning that the ease of methanisation was much improved.