A fuel-cell-type sensor for detection of formaldehyde in aqueous solution

A direct formaldehyde fuel cell using PtRu black as anode catalyst in membrane electrolyte assembly (MEA) has been fabricated for detecting formaldehyde in aqueous solution. The sensor shows high sensitivity for formaldehyde with good linearity over a wide concentration range from 0.002 to 1.25 mg ml−1 and the response time is within tens of seconds. According to voltammetric results, the PtRu black electrode shows a comparable electro-oxidizing catalytic activity for formaldehyde to methanol and high stability in monitoring formaldehyde through long-term test. By analyzing the results at different temperatures, the electrochemical reaction determines the response of the sensor, which is comparable to that of mass transfer process. Moreover, the effect of load resistance on the performance of the sensor was investigated: a small resistance is preferred for detecting higher concentrations and a high resistance is preferred for detecting lower concentrations. Through water absorption, the fuel-cell-type sensor can also detect gaseous formaldehyde concentration.