Publications by authors named "Anna K Farquhar"

Humidity- and temperature-dependent errors in concentrations reported by electrochemical sensors for atmospheric nitrogen dioxide significantly limit the reliability of the data. A basic understanding of the source of these errors has been missing. Empirical, software-based corrections are of limited reliability.

View Article and Find Full Text PDF

Redox flow batteries (RFBs) are promising energy storage candidates for grid deployment of intermittent renewable energy sources such as wind power and solar energy. Various new redox-active materials have been introduced to develop cost-effective and high-power-density next-generation RFBs. Electrochemical kinetics play critical roles in influencing RFB performance, notably the overpotential and cell power density.

View Article and Find Full Text PDF

An inexpensive, solution phase modification of flat carbon electrodes by electrochemical reactions of a 1,8-diaminonaphthalene derivative results in a 120- to 700-fold increase in capacity by formation of a 15-22 nm thick organic film. Modification of high surface area carbon electrodes with the same protocol resulted in a 12- to 82-fold increase in capacity. The modification layer contains 9-15% nitrogen present as -NH- redox centers that result in a large Faradaic component involving one H ion for each electron.

View Article and Find Full Text PDF

We have recently reported that reversible electrowetting can be observed on the basal plane of graphite, without the presence of a dielectric layer, in both liquid/air and liquid/liquid configurations. The influence of carbon structure on the wetting phenomenon is investigated in more detail here. Specifically, it is shown that the adsorption of adventitious impurities on the graphite surface markedly suppresses the electrowetting response.

View Article and Find Full Text PDF

Methods that reliably yield monolayers of covalently anchored modifiers on graphene and other planar graphitic materials are in demand. Covalently bonded groups can add functionality to graphitic carbon for applications ranging from sensing to supercapacitors and can tune the electronic and optical properties of graphene. Limiting modification to a monolayer gives a layer with well-defined concentration and thickness providing a minimum barrier to charge transfer.

View Article and Find Full Text PDF