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A Simple Method To Build Functionality Into Carbon Electrodes

Surface Chemistry: Straightforward technique requires no catalysts to add molecules to surfaces of electrodes used in fuel cells and sensors

by Leigh Krietsch Boerner
November 19, 2013

Easy Attachment
Schematic for attaching functional molecules to glassy carbon
Credit: Inorg. Chem.
A reaction between a glassy carbon surface decorated with azides and an organolithium alkyne (left) results in a triazolyllithium group (center). Chemists can then attach any number of different groups to the triazolyllithium, such as a ferrocene complex (right), to act as an electrocatalyst.

Attaching molecules to the glassy carbon electrodes used in fuel cells and electrochemical sensors just got easier thanks to chemistry reported in a new study (Inorg. Chem. 2013, DOI: 10.1021/ic402247n). The new technique lets scientists link functional molecules to a carbon surface without the need for catalysts or hard-to-synthesize materials, potentially simplifying the functionalization of electrodes.

Electrodes in fuel cells and sensors consist of a chemically inert surface—often carbon—decorated with functional groups that catalyze reactions as fluid reactants flow past. Unfortunately, past methods used to attach specific molecules to carbon needed either catalysts or a strained alkyne, which is tricky to make, says John A. S. Roberts, an electrochemist at the Pacific Northwest National Laboratory.

The new, easier method developed by Roberts and his colleagues helps functionalize electrodes by installing organolithium reagents on the carbon surfaces. Such groups can perform carbon-carbon coupling reactions to attach a wide range of functional groups to the surface.

To add these organolithium groups, the researchers first install azide groups on the glass carbon surface, and then react them with organolithium alkynes to form 1,2,3-triazolyllithium groups. As a proof of concept, the team attached a ferrocene compound to the surface groups—a difficult reaction which otherwise would have required a catalyst. They then used cyclic voltammetry to show that the ferrocene compound could do redox reactions after the attachment process. The whole process from bare electrode to ferrocene-coated one takes only three steps.

Because this method is simple and uses widely available reagents, it could greatly reduce the cost and the time for synthesis of carbon electrodes. “The idea here is to broaden the collection of things you can attach to carbon surfaces, to find a route that’s more synthetically flexible,” Roberts says.



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