Cobalt hydrotalcite-derived catalysts, doped with potassium, are active materials for the ethanol steam reforming reaction. Potassium addition reduces the acid sites number and strength. It acts as a promoter of the ethanol steam reforming (ESR); ethanol conversion is higher at lower temperature, as the amount of potassium at the surface of the catalyst increases. The catalysts are stable for long-term experiments (300 h) under high loads of ethanol and bioethanol (0.036 g(EtOH) min(-1), H2O:CH3CH2OH = 4:1 molar). Moreover, they generate a low amount of carbon (0.0067 gc g(catalyst)(-1) h(-1)). The catalysts after reaction contain almost exclusively high spin Co2+ in cobalt oxide (or in (Co,Mg)O); only traces of metallic cobalt are identified by magnetometry, <0.1 wt.% Co-0, suggesting that oxidized cobalt is an active species in ESR. (C) 2012 Elsevier B.V. All rights reserved.