Compact and efficient gas diffusion electrodes based on nanoporous alumina membranes for microfuel cells and gas sensors

• Published in: Analyst (London) Vol. 145; no. 1; pp. 122 - 131
• Main Authors: Fernandez, Wanda V, Tosello, Rocío T, Fernández, José L
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 16.12.2019
• Subjects: Aluminum oxide; Computer simulation; Constraining; Contact angle; Current density; Diffusion electrodes; Diffusion rate; Dissolved gases; Electrocatalysts; Electrolytes; Electrolytic cells; Flooding; Floods; Gas sensors; Gaseous diffusion; Gases; Hydrophobicity; Membranes; Organic chemistry; Oxidation; Platinum
• ISSN: 0003-2654; 1364-5528
• DOI: 10.1039/c9an01882d

This work describes the fabrication, characterization and evaluation of thin gas diffusion electrodes (GDEs) that are capable of electrocatalyzing the reaction of dissolved gases operating at high diffusion limiting current densities and with fast response times. Nanoporous alumina membranes (NAMs) were used as supports of metal electrocatalysts. NAMs were hydrophobized by silanization and coated on one side with Pt, either over the whole alumina surface by sputtering or just onto the pore openings by local chemical deposition. The Pt-modified NAM-based GDEs were evaluated for hydrogen oxidation. They operated by exposing their coated side to the electrolyte solution and the hydrophobic uncoated side to the flowing gas. Due to the NAM hydrophobicity, flooding of the pores by the electrolyte was diminished, so they were quickly filled by the circulating gas. Simulations of the process on single-pore GDEs showed that the dissolved gas diffused into the solution both radially (ideal pore) and linearly (partially flooded pore), reaching the electrocatalyst film placed right around the pore, which guaranteed a fast mass transport. Hydrogen oxidation operated on these NAM-based GDEs at a steady state with limiting current densities as high as 0.5 A cm −2 , which were attained in less than 5 s and were proportional to H 2 concentrations over a wide range. Thus, their potential use in microfuel cells and gas sensors was demonstrated. Gas diffusion electrodes based on nanoporous alumina membranes electrocatalyze hydrogen oxidation at high diffusion-limiting current densities with fast response times.