Homemade wet-proofing carbon papers with back-now effect were applied as backing layers in the cathode of passive air-breathing direct methanol fuel cell (DMFC) fed by pure methanol. With the increase of polytetrafluoroethylene (PTFE) content, the carbon papers exhibited different water transport resistance and generated different back-flow effects. Moreover. PTFE-treated carbon papers were observed by scanning electronic microscope (SEM) to investigate the function of the cross-linked microstructure. Maximum energy density (438 Wh L(-1)) of the improved pure methanol DMFC was obtained by using carbon paper with 40 wt.% PTFE content as the cathodic backing layer. This value was 6 times larger than that of the conventional DMFC fed by 2 M methanol solution. (C) 2011 Elsevier B.V. All rights reserved.