An electrode consisting of a mixture of quinhydrone (QH) and polybenzimidazole (PBI) with carbon was investigated as a solid reference electrode for hydrogen sensors. The vibrational behaviour of the polybenzimidazole/quinhydrone blend was investigated by infrared spectroscopy. The results suggest the existence of hydroquinone in the blend. The quinone/hydroquinone redox couple was evidenced by cyclic voltammetry. The potential of the solid-state reference electrode was found to be very stable over a period of 700 h. The drift was less than 0.1 mV per day. This electrode was successfully implemented in a potentiometric sensor. The standard potential was of the order of -550 mV at room temperature and increased as a function of the temperature with a slope of 1 mV/degreesC. The standard potential was also insensitive to changes in relative humidity (rh) in the sample gas over a period of I day. (C) 2003 Elsevier Ltd. All rights reserved.