Abstract
The nanotubular structures of IrO2 and Ir metal were successfully synthesized without any template. First, IrO2 nanotubes were prepared by electrospinning and post-calcination, where a fine control of synthetic conditions (e.g., precursor concentration and solvent composition in electrospinning solution, temperature increasing rate for calcination) was required. Then, a further thermal treatment of IrO2 nanotubes under hydrogen gas atmosphere produced Ir metal nanotubes. The electroactivity of the resultant Ir metal nanotubes was investigated toward carbon monoxide (CO) oxidation using linear sweep voltammetry (LSV) and amperometry. The anodic current response of Ir metal nanotubes was linearly proportional to CO concentration change, with a high sensitivity and a short response time. The amperometric sensitivity of Ir metal nanotubes for CO sensing was greater than a nanofibrous counterpart (i.e., Ir metal nanofibers) and commercial Pt (20 wt% Pt loading on carbon). Density functional theory calculations support stronger CO adsorption on Ir(111) than Pt(111). This study demonstrates that metallic Ir in a nanotubular structure is a good electrode material for the amperometric sensing of CO.
Highlights
The production of toxic gases, such as sulfur oxides, nitrogen oxides, hydrocarbons, and carbon monoxide (CO) has risen rapidly in the last few decades
We report the synthesis of IrO2 and Ir metal nanotubes without using any templates
The prepared IrO2 nanotubes were further reduced to Ir metal nanotubes under the thermal reduction process in H2 atmosphere
Summary
The production of toxic gases, such as sulfur oxides, nitrogen oxides, hydrocarbons, and carbon monoxide (CO) has risen rapidly in the last few decades. Electrochemical gas sensors have several advantages, including low detection limit, low power consumption, high stability and selectivity [3]. Amperometric gas sensors generally employ a variety of electrode materials catalyzing the electrochemical reactions of target analytes on the electrode surface. The amperometric sensing of CO requires electrode materials, which facilitate the oxidation of CO and are highly resistive to the poisoning. The mechanism for the CO oxidation in the aqueous acidic condition is shown as follows: CO + H2O → CO2 + 2H+ + 2e−
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