Palladium Nanosheet-Based Dual Gas Sensors for Sensitive Room-Temperature Hydrogen and Carbon Monoxide Detection

Abstract

Palladium has long been explored for use in gas sensors because of its excellent catalytic properties and its unique property of forming hydrides in the presence of H 2 . However, pure Pd-based sensors usually suffer from low response and a relatively high limit of detection. Palladium nanosheets (PdNS) are of particular interest for gas sensing applications due to their high surface area and excellent electrical conductivity. Here, we demonstrate the design and fabrication of low-cost PdNS-based dual gas sensors for room-temperature detection of H 2 and CO over a wide concentration range. We fabricated sensors using multiwalled carbon nanotube@PdNS (MWCNT@PdNS) composites and compared their performance against pure PdNS devices for hydrogen sensing based on electrical resistive response. Devices using PdNS alone had a response and response time of 0.4% and 50 s, respectively, to 1% H 2 in air. MWCNT@PdNS (1:5 mass ratio) showed enhanced performance at a lower hydrogen concentration with a limit of detection (LOD H 2 ) of 5 ppm. Nearly an order of magnitude increase in response was observed on increasing the amount of MWCNT to 50 mass % in the nanocomposite, but the response fell off at low H 2 concentration. Overall, these PdNS-based sensors were found to show good repeatability, stability, and performance under humid conditions. Their response was selective for H 2 versus CH 4 , CO 2 , and NH 3 ; the response to CO was comparable in magnitude but opposite in sign to the response to H 2 . Upon simultaneous exposure to equal concentrations (10 ppm each) of H 2 and CO, the response to CO was dominant. The PdNS showed high sensitivity to CO, detecting as little as 1 ppm CO in air at room temperature. The sensitivity to CO could be used either in a stand-alone room-temperature CO detector, where H 2 is known not to be present, or in combination with CO and combustible gas detectors to distinguish H 2 from other combustible gases.

Ultrathin Palladium Nanowires for Fast and Hysteresis-Free H2 Sensing

“…CO can strongly bind to the surface of Pd and interfere with H 2 sensing. 34 A 10% decrease in the sensor response was seen post-CO exposure. However, such a concentration of CO is much higher than the allowable CO concentrations in fuel cells (typically <0.2 ppm) 35 or in the ambient environment, for which our sensor is intended to be used.…”

“…To test the durability of the PdNW sensor, it was exposed to 100 ppm CO for 2 min, and the response of the sensor to 100 ppm H 2 was compared before and after this CO exposure (Figure S13). CO can strongly bind to the surface of Pd and interfere with H 2 sensing . A 10% decrease in the sensor response was seen post-CO exposure.…”

Pd Alloy Nanosheet Inks for Inkjet‐Printable H2 Sensors on Paper

“…The slightly higher response time of the paper‐based sensor compared to the IDE‐based sensor might be due to stacking of multiple layers of PdMoY NS which slows the H diffusion required to equilibrate the PdMoY NS with the gas and reach Δ R max . This somewhat sluggish response time is common in other 2D material‐based H 2 sensors including Pd films, [ 51 ] Pd alloy films, [ 37 ] and Pd‐decorated graphene based sensors. [ 52 ] The recovery time of the paper‐based sensor is shorter than that of the IDE‐based sensor due to the porous substrate which allows rapid diffusion of H 2 away from the PdMoY NS.…”

“…A similar result was reported in our previous work. [ 51 ] Figure 4d presents the response of a paper‐based PdMoY NS sensor to 100 ppm of H 2 , CO, CH 4 , or CO 2 in air. Compared to the IDE‐based sensor, for which the responses to H 2 and CO were comparable in magnitude, the paper‐based sensor has a comparatively larger response to H 2 than CO and negligible response to CH 4 and CO 2 .…”

An Improved Humidity Sensor with GO-Mn-Doped ZnO Nanocomposite and Dimensional Orchestration of Comb Electrode for Effective Bulk Manufacturing

“…Hence, maintaining the layer-by-layer spacing in Mxene without water intercalation at high humidity levels is a major limitation. Generally, MXene is prone to degradation when it encounters oxygen and water in the air, reducing its long-term stability performance under highly humid environmental conditions [ 20 , 21 , 22 ]. This requires more maintenance of material after preparation.…”