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

Abstract

chemical, [5] gas, humidity, [6] and strain sensing applications. [7,8] Various types of paper-based sensors have been reported, and these can be broadly categorized as optical sensors and electrochemical sensors. Optical sensors include colorimetric, surface-enhanced Raman spectroscopy, and fluorescence sensors, whereas electrochemical sensors include voltammetrybased, potentiometric, and chemiresistive sensors. [9] Chemiresistive sensors are preferred for gas sensing applications due to their low-cost fabrication, portability, and easy-to-read output. [10] In contrast to paper-based chemical sensors and biosensors that are typically disposable, [11] gas sensors, especially chemiresistive sensors, can be used to reversibly detect gases over extended periods of time. Hence, paper-based chemiresistive sensors are promising as ultra-low-cost chemiresistive sensors for gases such as NO 2 , [12] NH 3 , [13] H 2 S, [14] and H 2 . [15] Such paper-based chemiresistive gas sensors often outperform sensors using other (nonporous) substrates such as silicon or polymers, due to synergistic effects of the flexible porous paper coupled with simplicity of fabrication and use. [16] Hydrogen is a highly explosive gas with a lower explosion limit of 4% in air. It also has high diffusivity through many materials due to its small size, creating challenges in safely storing and transporting it. [17] These limitations are a key factor influencing future development of a H 2 -based energy economy. Hence, even with its obvious advantages such as high energy density, compatibility with efficient fuel cells, and carbon-free combustion products, the role of H 2 as a next generation fuel remains uncertain. [18] The cost of H 2 sensors is a significant factor in widespread adoption of H 2 as a fuel, as such sensors will be required at H 2 production units, distribution units, and in H 2 fuel cell-powered vehicles. The US Department of Energy (DOE) has set cost targets for such H 2 sensors, with an ambitious goal of <$15 per sensor for fuel cellpowered vehicles. [19] This goal for low-cost H 2 sensors could be achieved using paper-based Pd chemiresistive H 2 sensors. Pd can selectively absorb a large amount of H 2 at room temperature and form palladium hydride, PdH x , changing both the volume and resistivity of the Pd. [18] Although the material cost of Pd is higher than most conventional metals, low operating cost and selective room-temperature H 2 detection make 2D palladium nanostructures enable sensitive room-temperature detection of H 2 . However, they can be limited by stability and fabrication costs. Stability may be improved by alloying Pd with other metals, while cost could be reduced by using paper as a substrate. An ultra-low-cost sensor using Pd alloy (PdMoY) nanosheets (NS) on paper is reported. The 2D Pd alloy nanosheets are prepared by a solution-phase route, drop cast onto paper (≈1 × 1 cm) with silver contacts drawn on it, and dried. The same material is deposited on an interdigitated electrode (IDE). Both sensors are teste...

Review—Recent Progress in the Design of Chemical Hydrogen Sensors

“…12. 91 This work on inkjet-printable hydrogen sensor provides important insights for the future development of hydrogen gas sensors, as it combines high performance with low cost. This study introduces a groundbreaking concept by combining PdMoY NS of an undisclosed composition with solution processing and paper substrates, resulting in a roomtemperature hydrogen sensor that is both high-performance and flexible, while remaining costless.…”

A Review of Paper-Based Sensors for Gas, Ion, and Biological Detection

“…Some researchers focused on other gases such as H 2 , NH 3 , and H 2 S. Abhishek Kumar et al [59] used PdMoY alloy nanosheets (NS) to detect hydrogen (H 2 ) in the air, and the Pd alloy 2D solution-phase NS were prepared and then drop cast onto paper (≈1 × 1 cm) on which silver contacts were drawn and dried. The same substance content was deposited on an interdigitated electrode (IDE).…”

Paper-Based Hydrogen Sensors Using Ultrathin Palladium Nanowires

“…Our previous investigations on chemiresistive H 2 sensors show that fast response and recovery times can be achieved using Pd nanowires. , However, despite the small quantities of Pd nanowires used, the cost of these sensors remained relatively high due to the use of gold-coated interdigitated electrodes (IDEs) that require a cleanroom environment and sophisticated equipment to fabricate. Although some work has been done on paper-based H 2 sensors using nanoparticles − and Pd nanosheets, Pd nanowires have not previously been explored for paper-based H 2 sensors despite their obvious advantages. This may be because most PdNW chemiresistive sensor studies to date have used lithographically patterned PdNWs that are incompatible with a paper substrate. , …”

“…Although some work has been done on paper-based H 2 sensors using nanoparticles 17−19 and Pd nanosheets, 20 Pd nanowires have not previously been explored for paper-based H 2 sensors despite their obvious advantages. This may be because most PdNW chemiresistive sensor studies to date have used lithographically patterned PdNWs that are incompatible with a paper substrate.…”