Steam reforming of methane (SRM) is the primary method to produce hydrogen. Commercial Ni-based catalysts have been optimized for SRM with excess steam (H2O/CH4 > 2.5) at high temperatures (>700 degrees C). However, commercial catalysts are not suitable under severe reaction conditions such as stoichiometric steam over methane ratio (H2O/CH4 = 1.0) and low temperature (600 degrees C). In this study, SRM has been carried out at a gas hourly space velocity (GHSV) of 155426 h(-1) over Ni-Ce((1-x))Z((x))O(2) catalysts prepared by a co-precipitation method. The CeO2/ZrO2 ratio was systematically varied to optimize Ni-Ce(1-x)Zr(x)O2 catalysts at a H2O/CH4 ratio of 1.0 and at 600 degrees C. 15 wt.% Ni-Ce0.8Zr0.2O2 exhibited the highest CH4 conversion as well as stability with time on stream due to high oxygen storage capacity. (C) 2011 Elsevier Ltd. All rights reserved.