Macroporous platinum electrodes for hydrogen oxidation in ionic liquids

Permeable Weldable Elastic Fiber Conductors for Wearable Electronics

Elastic fiber conductors are advantageous for applications in wearable electronics due to their small size, light weight, and excellent integration ability. Here, we report the fabrication of elastic fiber conductors with a three-dimensional (3D) porous structure using electrospun thermoplastic elastomer (TPE) microfibers and silver nanoparticles (AgNPs) as the building blocks. With the 3D porous structure, such a fiber is highly permeable to gases and liquids. As such, the performance of the fiber in many applications of wearable electronics (especially wearable sensors and detectors) can be improved significantly. Benefitting from the excellent processability of TPE and dispersibility of AgNPs, the fiber is highly compatible with thermal and solvent welding. In addition, the fiber also possesses super stretchability, high conductivity, and robust endurance to deformation. As a proof-of-concept application, we demonstrate that a rope-shaped capacitor made by plying one pair of such fibers can detect the volume change of artificial sweat with 17-times higher sensitivity than the capacitor using nonporous fibers as electrodes. We further demonstrate that, by integrating two groups of perpendicularly arranged fibers into a monolithic porous mat, sensitive matrix-addressed monitoring of artificial sweat can be realized.

Formation of 3-Dimensional Gold, Copper and Palladium Microelectrode Arrays for Enhanced Electrochemical Sensing Applications

Microelectrodes offer higher current density and lower ohmic drop due to increased radial diffusion. They are beneficial for electroanalytical applications, particularly for the detection of analytes at trace concentrations. Microelectrodes can be fabricated as arrays to improve the current response, but are presently only commercially available with gold or platinum electrode surfaces, thus limiting the sensing of analytes that are more electroactive on other surfaces. In this work, gold (Au), copper (Cu), and palladium (Pd) are electrodeposited at two different potentials into the recessed holes of commercial microelectrode arrays to produce 3-dimensional (3D) spiky, dendritic or coral-like structures. The rough fractal structures that are produced afford enhanced electroactive surface area and increased radial diffusion due to the 3D nature, which drastically improves the sensitivity. 2,4,6-trinitrotoluene (TNT), carbon dioxide gas (CO₂), and hydrogen gas (H₂) were chosen as model analytes in room temperature ionic liquid solvents, to demonstrate improvements in the sensitivity of the modified microelectrode arrays, and, in some cases (e.g., for CO₂ and H₂), enhancements in the electrocatalytic ability. With the deposition of different materials, we have demonstrated enhanced sensitivity and electrocatalytic behaviour towards the chosen analytes.

Fast responding hydrogen gas sensors using platinum nanoparticle modified microchannels and ionic liquids

From a safety perspective, it is vital to have fast responding gas sensors for toxic and explosive gases in the event of a gas leak. Amperometric gas sensors have been developed for such a purpose, but their response times are often relatively slow - on the order of 50 seconds or more. In this work, we have developed sensors for hydrogen gas that demonstrate ultra-fast response times. The sensor consists of an array of gold microchannel electrodes, electrodeposited with platinum nanoparticles (PtNPs) to enable hydrogen electroactivity. Very thin layers (∼9 μm) of room temperature ionic liquids (RTILs) result in an extremely fast response time of only 2 s, significantly faster than the other conventional electrodes examined (unmodified Pt electrode, and PtNP modified Au electrode). The RTIL layer in the microchannels is much thinner than the channel length, showing an interesting yet complex diffusion pattern and characteristic thin-layer behavior. At short times (e.g. on the timescale of cyclic voltammetry), the oxidation current is smaller and steady-state in nature, compared to macrodisk electrodes. At longer times (e.g. using long-term chronoamperometry), the diffusion layer is large for all surfaces and extends to the liquid/gas phase boundary, where the gas is continuously replenished from the flowing gas stream. Thus, the current response is the largest on the microchannel electrode, resulting in the highest sensitivity and lowest limit of detection for hydrogen. These microchannel electrodes appear to be highly promising surfaces for the ultrafast detection of hydrogen gas, particularly at relevant concentrations close to, or below, the lower explosive limit of 4 vol-% H₂.