A robust methanol concentration sensing technique in direct methanol fuel cells and stacks using cell dynamics

The electrochemical behaviour of direct methanol fuel cells (DMFCs) is sensitive to methanol concentration; thus, to avoid external sensors, it is a promising candidate to monitor the concentration of methanol in the fuel circulation loop, which is central to the efficient operation of direct methanol fuel cell systems. We address this issue and report on an extremely robust electrochemical methanol sensing technique that is not sensitive to temperature, cell degradation and membrane electrode assembly (MEA) type. We develop a temperature independent empirical correlation of the dynamic response of cell voltage to step changes in current with methanol concentration. This equation is successfully validated under various operating scenarios at both the single cell and stack levels. Our sensing method achieves an impressive accuracy of ±0.1 M and this is expected to increase the reliability of methanol sensing and simplify the control logic of DMFC systems.