Abstract: The disclosure provides in its first aspect a catalyst system for gas-phase electrolysis of a reactant gas to form a product in an aqueous medium, the catalyst system comprising a catalytic material; an ion-conducting polymer layer provided on the catalytic material and comprising an ion-conducting polymer that includes hydrophilic and hydrophobic groups. Said catalyst system is remarkable in that the ion-conducting polymer layer has a thickness of 2 nm to 50 nm measured by transmission-electron microscopy. In its second aspect, the disclosure provides a method of manufacturing a catalyst system for gas-phase electrolysis of reactant gas to produce a product in an aqueous medium preferably according to the first aspect. The use of the catalyst system in accordance with the first aspect in the electrochemical production of at least one multi-carbon compound from a carbon-containing gas or of at least one product from a reactant gas is also disclosed.