A Highly Sensitive and Stable rGO:MoS2-Based Chemiresistive Humidity Sensor Directly Insertable to Transformer Insulating Oil Analyzed by Customized Electronic Sensor Interface

Reduced graphene oxide and molybdenum disulfide (rGO:MoS2) are the most representative two-dimensional materials, which are promising for a humidity sensor owing to its high surface area, a large number of active sites, and excellent mechanical flexibility. Herein, we introduced a highly sensitive and stable rGO:MoS2-based humidity sensor integrated with a low-power in-plane microheater and a temperature sensor, directly insertable to transformer insulating oil, and analyzed by a newly developed customized sensor interface electronics to monitor the sensor's output variations in terms of relative humidity (RH) concentration. rGO:MoS2 sensing materials were synthesized by simple ultrasonication without using any additives or additional heating and selectively deposited on titanium/platinum (Ti/Pt) interdigitated electrodes on a SiO2 substrate using the drop-casting method. The significant sensing capability of p-n heterojunction formation between rGO and MoS2 was observed both in the air and transformer insulating oil environment. In air testing, the sensor exhibited an immense sensitivity of 0.973 k Omega/%RH and excellent linearity of similar to 0.98 with a change of humidity from 30 to 73 %RH, and a constant resistance deviation with an inaccuracy rate of 0.13% over 400 h of continual measurements. In oil, the sensor showed a high sensitivity of 1.596 k Omega/%RH and stable repeatability for an RH concentration range between 34 and 63 %RH. The obtained results via the sensor interface were very similar to those measured with a digital multimeter, denoting that our developed total sensor system is a very promising candidate for real-time monitoring of the operational status of power transformers.

Automated summary

The study presented a highly sensitive humidity sensor based on rGO:MoS2, which exhibited significant sensing performance in both air and transformer insulating oil environments. The sensor demonstrated excellent linearity, stable repeatability, and accurate monitoring results, making it a very promising candidate for real-time monitoring of power transformer operational status.