A fuel cell based amperometric room temperature hydrogen sensor with Nafion as proton conducting electrolyte, Pd as sensing electrode, Pt as both counter and reference electrodes has been developed. Sensing electrode was prepared by electrodeposition of Pd on carbon gas diffusion electrode using room temperature ionic liquid electrolyte. Pt spray coated on gas diffusion electrode forms the counter electrode in the sensor. Pd electrodeposition was carried out at an applied potential of -1.0 V vs Pd wire and resulted in the formation of Pd clusters. The microstructure of electrodeposited Pd was investigated using field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The crystal structure of the Pd nanoparticles was indexed to face centered cubic by X-ray diffraction (XRD) and selected area electron diffraction (SAED). X-ray photoelectron spectroscopy (XPS) confirmed metallic form of the deposited Pd nanoparticles. The scratch test endorsed the fact that Pd nanoparticles adhered firmly to the surface of the gas diffusion electrode and it is found to be stable up to the load of 2 N. Range of response of the sensor to H-2 was in the concentration range 1% to 5% and found to be linear. (C) The Author(s) 2017. Published by ECS. All rights reserved.