Overall Design of a Gradient-Ordered Membrane Electrode Assembly for Direct Liquid Fuel Cells

The direct liquid fuel cell (DLFC) constitutes a promising energy conversion system that directly conveys the chemical energy of liquid fuels into electrical energy. In certain DLFCs, gas is produced as a product of electrochemical reactions during operation. However, the accumulation of gas inside the porous electrode can significantly hinder the transport of reactants, leading to the failure of active sites and severe concentration loss. To address this issue, a gradient-ordered membrane electrode assembly (MEA) is designed and fabricated, consisting of a dual-gradient diffusion layer that comprises a pore-size gradient and a wettability gradient as well as a catalyst layer constructed by nanoneedle catalyst. This MEA promptly removes the produced gas and delivers the fresh solution, thereby enhancing the cell power output and stability. The fuel cell with the gradient-ordered MEA achieves a remarkable peak power density of 177 mW cm⁻² and a discharging time of 19 h, which are more than four times and 30 times, respectively, higher than those of the conventional MEA.