A new process is developed to fabricate a highly sensitive and selective hydrogen sensor by depositing a partially crystalline and highly oriented film of MoS2 from its single layer suspension on an alumina substrate. When these films are promoted with some catalysts selected from Pt-group metals (Pt, Pd, Ru or any combination of these metals) they exhibit a high sensitivity and selectivity to hydrogen gas. Unlike other metal oxide sensors which are sensitive to many reducing and oxidizing gases and operate at a temperature of 350 degrees C or higher, this sensor is highly selective to hydrogen gas and its operating temperature is from 25 to 150 degrees C. The lower operating temperature enhances safety when dealing with hydrogen gas. The sensor response to hydrogen at 120 degrees C is linear in concentration from 30 to 10(4) ppm with a 10 to 30 second response time and a 45 to 90 second recovery time. Above 10(4) ppm the sensor is still linear but the slope of conductance versus hydrogen concentration changes.