Microfluidics for Electrochemical Energy Conversion

Abstract

Electrochemical energy conversion is an important supplement for storage and on-demand use of renewable energy. In this regard, microfluidics offers prospects to raise the efficiency and rate of electrochemical energy conversion through enhanced mass transport, flexible cell design, and ability to eliminate the physical ion-exchange membrane, an essential yet costly element in conventional electrochemical cells. Since the 2002 invention of the microfluidic fuel cell, the research field of microfluidics for electrochemical energy conversion has expanded into a great variety of cell designs, fabrication techniques, and device functions with a wide range of utility and applications. The present review aims to comprehensively synthesize the best practices in this field over the past 20 years. The underlying fundamentals and research methods are first summarized, followed by a complete assessment of all research contributions wherein microfluidics was proactively utilized to facilitate energy conversion in conjunction with electrochemical cells, such as fuel cells, flow batteries, electrolysis cells, hybrid cells, and photoelectrochemical cells. Moreover, emerging technologies and analytical tools enabled by microfluidics are also discussed. Lastly, opportunities for future research directions and technology advances are proposed.

Electrochemistry in Magnetic Fields

“…Microfluidics is the science which studies the behavior of fluids through microchannels and the technique of manipulating fluids in small conduits having at least one submillimeter dimension [72] . In electrochemistry, microfluidics may also take advantage of precise flow control, targeted species directional transportation, and optimal thermodynamic equilibrium [72, 73] . A simple representative schematic of a microfluidic flow cell is shown in Figure 16.…”

On the challenges of materials and electrochemical characterization of concentrated electrolytes for redox flow batteries

“…Custom-made cell configurations ( e.g. , microfluidic electrochemical devices 59 ) may also find utility in evaluating concentrated electrolytes by further quantifying transport descriptors. For example, a Hittorf cell can be constructed to estimate the cation transference number for a concentrated binary electrolyte.…”

“…Further, existing microelectrode theory has been well-developed for dilute solutions, 54 but the theory behind microelectrode models becomes complicated in the concentrated solution regime; it requires many parameters to be accurately estimated (e.g., solute-solute interaction coefficients), 11 it may necessitate the formulation of additional modes of mass transport (e.g., migration, Faradaic convection), 55 and it may require knowledge of chemical-specific phenomena such as aggregation and nano-heterogeneity. 12,56 Custom-made cell configurations (e.g., microfluidic electrochemical devices 57 ) may also find utility in evaluating concentrated electrolytes by further quantifying transport descriptors. For example, a Hittorf cell can be constructed to estimate the cation transference number for a concentrated binary electrolyte.…”

Copper nanoparticles suitable for bifunctional cholesterol oxidation reaction: harvesting energy and sensor

“…Consequently, one of the main problems of these microfluidic devices is the electrodes composition and the flow through them. On the other hand, one of the most important advantages is that different fuels can be used to produce energy and be quantified; fuels such as glucose, ethanol, methanol and glycerol have been reported [5,6]. One molecule that has received few attention as a fuel in studies is cholesterol, although it is of high biomedical interest for the continuous control of cholesterol in blood serum to minimize the risk of cardiovascular diseases [7].…”