Operating direct methanol fuel cells (DMFCs) with concentrated fuel is desired to increase the energy density of the power pack. In this paper, we propose and fabricate a micro-porous anode current collector, which enables a passive DMFC to operate with methanol solutions as concentrated as 22.0 M without sacrificing the performance generated with diluted methanol. It is found that the micro-porous current collector allows an accumulation of CO2 gas in the porous structure, forming a barrier to resist the transport of methanol to the catalyst layer. The reduced methanol concentration level in the anode catalyst layer tends to reduce the rate of methanol crossover and hence, improve the performance. (C) 2014 Elsevier Ltd. All rights reserved.