Low-power, room-temperature electrochemical hydrogen sensors are critical for safe hydrogen utilization. Here, we report a room-temperature mixed-potential H2 sensor using a Pd-decorated epoxy-controlled graphene oxide (Pd-epGO) sensing electrode, which is paired with a cerium-doped graphene oxide (Ce-GO) proton-conducting membrane and a reference electrode with an oxygen-reduction activity. The Ce-GO membrane provides high proton conductivity via interlayer expansion and stabilized hydration, while epoxide-controlled GO enables homogeneous dispersion of ultrasmall Pd nanoparticles (∼2.5 nm) and efficient electronic conduction after reduction. By engineering the reference electrode with an active ORR catalyst (La0.5Sr0.5CoO1−δ (LSCO)) integrated with reduced epGO to maintain a stable oxygen electrode potential and suppress H2-crossover-induced mixed potentials, the sensor exhibits enhanced potentiometric sensitivity (134 mV decade–1) and a clear logarithmic response over 10–1,000 ppm of H2 with rapid room-temperature dynamics. Electrochemical analysis clarifies how competitive HOR/ORR kinetics at both electrodes determine the output, establishing reference-electrode selection as a key design principle for improving low-temperature H2 sensing.
Siga et al. (Wed,) studied this question.