The model of anode catalyst layer performance in a direct methanol fuel cell is developed. The model takes into account finite rate of methanol adsorption on the catalyst surface. The solution to the problem is reduced to calculation of integral. This solution reveals a novel mode of the catalyst layer operation: the regime with variable thickness of current-generating domain. Local current in this regime is generated in a sub-layer adjacent to the membrane; the thickness of this sub-layer increases with the increase in total current. Voltage loss in this regime is minimal. Conditions when this regime is realized are obtained and the physics of the effect is discussed.