The cavity-microelectrode as a tip for scanning electrochemical microscopy

• A Au-based cavity-microelectrode with correct geometry to be used as tip for the scanning electrochemical microscope was prepared and described
• This tip compensates for the lack of commercial microwire for building SECM tips using the conventional methods
• The C-ME tip can be easily filled with any finely dispersed material and used for positioning through approach curves
• The C-ME tip is useful for several modes of SECM, including feedback and generation/collection ones.

In this work, we present and discuss the use of cavity-microelectrodes (C-MEs) used as tip for the scanning electrochemical microscopy (SECM). Cavity-microelectrodes can be filled with a desired finely dispersed material thus compensating for the limited commercial availability of microwires. After discussing the possibility of filling and emptying a cavity-microelectrode with a desired tip shape, the consistency of negative and positive feedback approach curves obtained after filling a Au C-ME was verified. In addition, the tip/C-ME was tested under gas (oxygen) evolution condition, in order to demonstrate that the filling is stable in a wide range of gas fluxes thus extending the possible applications to tip generation/substrate collection mode. Finally, we introduce the use of the proposed system to quantify the rates of parallel reactions occurring at the material inserted in the tip under the tip generation/substrate collection mode.

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