Catalytic steam reforming of methane in an electric field (named "electreforming") was conducted over metal catalysts supported on CeO2 or CexZr1-xO2 at low temperatures such as 423 K where conventional catalytic reactions hardly proceeded. The conversion of methane was greatly increased by weak and effective application of an electric field to the catalyst bed. Use of CexZr1-xO2 as a catalyst support promoted electreforming, the lattice oxygen of CexZr1-xO2 playing an important role. Energy efficiency of electreforming, reaction mechanism, and the role of lattice oxygen were investigated and are discussed in this paper. (C) 2011 Elsevier B. V. All rights reserved.