The reaction of CO2 hydrogenation is of high environmental interest since it allows for the transformation of the logistically challenging H-2, gained from renewable sources, to the much more manageable hydrocarbons. Ruthenium is a catalyst widely used to produce methane from CO2. In this study we present an example of how Electrochemical Promotion of Catalysis (EPOC) can elucidate the role of solid electrolytes (YSZ, BZY) supporting Ru porous films or nanoparticles. It is found that the sign of the charge (-/+) of the current-conducting species of the electrolyte has a profound effect on the selectivity of Ru during CO2 hydrogenation. Using this insight, we have developed and tested a new supported Ru-Co catalyst for the production of higher hydrocarbons.