In this work, we present an investigation on Pt/graphene/GaN devices for hydrogen gas sensing applications. The graphene layer was deposited on GaN substrate using a chemical vapour deposition (CVD) technique and was characterised via Raman and X-ray photoelectron spectroscopy. The current-voltage (I-V) and dynamic response of the developed devices were investigated in forward and reverse bias operation at an optimum temperature of 160 degrees C. Voltage shifts of 661.1 and 484.9 mV were recorded towards 1% hydrogen at forward and reverse constant bias current of 1 mA, respectively.