A Tortuosity Engineered Dual-Microporous Layer Electrode Including Graphene Aerogel Enabling Largely Improved Direct Methanol Fuel Cell Performance with High-Concentration Fuel

Methanol crossover is an important factor affecting the performance of direct methanol fuel cells (DMFCs). In this work, a novel membrane electrode assembly (MEA) is designed and prepared by adding a layer of graphene aerogel (GA) between the carbon powder microporous layer and the catalytic layer, which optimizes the methanol transport and improves the output performance of DMFC at high methanol concentrations. Compared to conventional carbon powder, the addition of GA increases the tortuosity of the anode in the through-plane direction; hence, methanol is diluted to a suitable concentration when it reaches the catalyst. The maximum power density of the novel MEA can reach 27.4 mW·cm−2 at a condition of 8 M methanol, which is 234% higher than that of the conventional electrode. The test results of electrochemical impedance spectroscopy (EIS) indicate that the addition of GA does not increase the internal resistance of the novel MEA and that the mass transfer resistance at high concentrations is significantly lower. The experimental results indicate that the output performance at high concentration can be significantly improved by adding a GA layer, and its practicability in portable devices can be improved. It also improves the stability of DMFC under long-term testing.