Prospects of membraneless mixed-reactant microfluidic fuel cells: Evolution through numerical simulation

Mixed-reactant microfluidic membraneless fuel cells are promising power sources for future electronic portable applications due to their simplified construction and operation. In order to develop a better performing mixed-reactant fuel cell, the improvement of elements such as selective catalysts and optimization of electrode-microchannel arrangements for cell stacking is of key importance. While we have previously worked on the catalysts approach, the next step is naturally to develop a microfluidic device for low power applications. Thus, this work focuses on developing a passive mixed-reactant fuel cell stack through numerical simulation studies, which allow better understanding of the phenomena occurring in the device and optimizing cell parameters based on simulation results. Two electrode arrangements were studied and the model pointed out the option with better fuel utilization and better oxygen supply, hence, stronger performance. The design was further improved by reducing the resistance between the electrodes, as indicated by the simulation. The resulting device was then fabricated and tested, reaching a maximum power density of 28 mW cm⁻² with 4 M MeOH and it exhibited stable operation during at least 6 h. Based on this results, 4 mixed-reactant cells were incorporated in a single microfluidic device. The stack was tested in passive conditions producing 1.0 mW of peak power in series connection and it exhibited a stable operation. Moreover, the proof of concept was demonstrated by using the stack for powering a green LED during 4 h with a single charge of 234 μL.