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Dynamic Tuning of a Thin Film Electrocatalyst by Tensile Strain.

ABSTRACT: We report the ability to tune the catalytic activities for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) by applying mechanical stress on a highly n-type doped rutile TiO₂ films. We demonstrate through operando electrochemical experiments that the low HER activity of TiO₂ can reversibly approach those of the state-of-the-art non-precious metal catalysts when the TiO₂ is under tensile strain. At 3% tensile strain, the HER overpotential required to generate a current density of 1?mA/cm² shifts anodically by 260?mV to give an onset potential of 125?mV, representing a drastic reduction in the kinetic overpotential. A similar albeit smaller cathodic shift in the OER overpotential is observed when tensile strain is applied to TiO₂. Results suggest that significant improvements in HER and OER activities with tensile strain are due to an increase in concentration of surface active sites and a decrease in kinetic and thermodynamics barriers along the reaction pathway(s). Our results highlight that strain applied to TiO₂ by precisely controlled and incrementally increasing (i.e. dynamic) tensile stress is an effective tool for dynamically tuning the electrocatalytic properties of HER and OER electrocatalysts relative to their activities under static conditions.

SUBMITTER: Benson EE

PROVIDER: S-EPMC6828675 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Dynamic Tuning of a Thin Film Electrocatalyst by Tensile Strain.

Benson Eric E EE Ha Mai-Anh MA Gregg Brian A BA van de Lagemaat Jao J Neale Nathan R NR Svedruzic Drazenka D

Scientific reports 20191104 1

We report the ability to tune the catalytic activities for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) by applying mechanical stress on a highly n-type doped rutile TiO2 films. We demonstrate through operando electrochemical experiments that the low HER activity of TiO2 can reversibly approach those of the state-of-the-art non-precious metal catalysts when the TiO2 is under tensile strain. At 3% tensile strain, the HER overpotential ...[more]

PMID: 31685891

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Project description:Wearable mechanical sensors have the potential to transform healthcare by enabling patient monitoring outside of the clinic. A critical challenge in the development of mechanical-e.g., strain-sensors is the combination of sensitivity, dynamic range, and robustness. This work describes a highly sensitive and robust wearable strain sensor composed of three layered materials: graphene, an ultrathin film of palladium, and highly plasticized PEDOT:PSS. The role of the graphene is to provide a conductive, manipulable substrate for the deposition of palladium. When deposited at low nominal thicknesses (~8 nm) palladium forms a rough, granular film which is highly piezoresistive (i.e., the resistance increases with strain with high sensitivity). The dynamic range of these graphene/palladium films, however, is poor, and can only be extended to ~10% before failure. This fragility renders the films incompatible with wearable applications on stretchable substrates. To improve the working range of graphene/palladium strain sensors, a layer of highly plasticized PEDOT:PSS is used as a stretchable conductive binder. That is, the conductive polymer provides an alternative pathway for electrical conduction upon cracking of the palladium film and the graphene. The result was a strain sensor that possessed good sensitivity at low strains (0.001% engineering strain) but with a working range up to 86%. The piezoresistive performance can be optimized in a wearable device by sandwiching the conductive composite between a soft PDMS layer in contact with the skin and a harder layer at the air interface. When attached to the skin of the torso, the patch-like strain sensors were capable of detecting heartbeat (small strain) and respiration (large strain) simultaneously. This demonstration highlights the ability of the sensor to measure low and high strains in a single interpolated signal, which could be useful in monitoring, for example, obstructive sleep apnea with an unobtrusive device.

Dataset Information

Dynamic Tuning of a Thin Film Electrocatalyst by Tensile Strain.

Publications

Dynamic Tuning of a Thin Film Electrocatalyst by Tensile Strain.

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