Scanning electrochemical microscopy at variable temperatures.

All chemical reactions are influenced by temperature, however, temperature is usually not considered an important parameter which has to be varied or at least controlled in SECM measurements. A precise temperature-control unit was designed and integrated into a SECM setup which allows setting the temperature of the sample and the adjacent electrolyte in a range between 0 and 100 °C without causing convection. Data acquisition was synchronized with the current pulses through the Peltier element to decrease the noise and keep the tip-to-sample distance constant during imaging. SECM images in the feedback mode, generator collector mode and the redox competition mode for model samples such as an enzyme entrapped within a polymer spot or oxygen reduction catalysts demonstrate the importance of controlling temperature as well as performing SECM experiments at predefined and constant increased temperature.

Electrochemical synthesis of core-shell catalysts for electrocatalytic applications.

A novel electrochemical method to prepare platinum shells around carbon-supported metal nanoparticles (Ru and Au) by pulsed electrodeposition from solutions containing Pt ions is presented. Shell formation is confirmed by characteristic changes in the cyclic voltammograms, and is further evidenced by monitoring particle growth by transmission electron microscopy as well as by energy-dispersive analysis of X rays (EDX). Scanning electrochemical microscopy and EDX measurements indicate a selective Pt deposition on the metal/carbon catalyst, but not on the glassy carbon substrate. The thus prepared carbon-supported core-shell nanoparticles are investigated with regard to their activity in electrocatalytic oxygen reduction, which demonstrates the applicability of these materials in electrocatalysis or sensors.