Understanding Mass Transport at Channel Microband Electrodes: Influence of Confined Space under Stagnant Conditions

A microfluidic electrochemical sensing platform for in situ detection of trace cadmium ions

Among various detection and analysis platforms, a microfluidic chip-based electrochemical sensing detection platform is a new type of detection platform. In this study, a microfluidic electrochemical detection platform for cadmium ion detection is proposed, and the performance of the detection platform is optimized in terms of both the microchannel size and electrode modifications. The detection mixing processes of the detector with different microchannel sizes, including the concentration distribution in the channel, pressure decay variation and electrolyte current density variation in the detector, were investigated by finite element model calculations. The analysis shows that the size of the microchannel in the detector affects the fluid and thus further affects the chemical reaction. If the size of the electrode does not match the size of the microchannel, insufficient sample volume will lead to inaccurate measurements, reduced sensitivity and increased detection limits. It was found that the sensitivity of the electrochemical sensor was highest when the size of the microchannel in the chip was 400 μm. After optimization, the optimal detection limit for cadmium ions was 0.03 μg L^-1 (S/N = 3). The proposed sensing platform is simple in design and stable in structure, and is suitable for field screening and rapid response to heavy metal contamination events.

A new electrochemical cell with a uniformly accessible electrode to study fast catalytic reactions

The electrochemical study of fast catalytic reactions is limited by mass transport when using the conventional electrochemical cell with a rotating disk electrode (RDE). To overcome this issue, it is important to find a new device with improved transport properties that respects electrochemical constraints. We used numerical simulations of computational fluid dynamics to design a new electrochemical cell based on the so-called "jet flow" design for the kinetic studies of catalytic chemical reactions at the surface of an electrode. The new cell is characterized by a high, reliable and uniform mass transport over the electroactive part of its surface. We investigated the effects of the nozzle and the electrode diameters, the nozzle-electrode distance and the Reynolds number on the performance of the jet-electrode in the flow system. Through the optimization of the geometry of this jet electrode cell, we achieved a factor of 3 enhancement in transport compared to the rotating disk electrode. We succeeded in constructing the designed electrode, characterized it with electrochemical techniques, and found an excellent agreement between the transport properties deduced from the numerical simulations and those from the measurements.