waste electrical and electronic equipment (WEEE) generated after their disposal. The large quantities of WEEE and the wide variety of materials they often contain (ferrous metals, nonferrous metals, noblemetal, chemicals, glass, and plastics) have raised a serious alarm on their potential adverse health and environmental consequences when incorrectly disposed of. Moreover, this waste can be regarded as a resource of valuable materials (e.g., Au, Pt, Li) that if not recovered, has to be extracted again, resulting in natural resource depletion and environmental degradation. Recovering these metals and satisfying the demand for cheap secondhand equipment has become profitable business in emerging economies, which has turned Asia (in particular, China and India) and Africa into recipients of 90% of globally exported WEEE. [1] However, dismantling procedures are often carried out in inappropriate infrastructures with discarded components being openly incinerated and disposed of in unlined landfills that lack monitoring of leachate recovery systems of any kind. Due to their content of heavy metals, batteries are one of the most hazardous components of e-waste. For this reason, many Organization of Economic Cooperation and Development (OECD) countries have established regulations on the maximum permitted content of certain metals such as mercury or cadmium and the mandatory recycling of spent batteries. [2] Lithium-ion batteries are today the most predominant energy sources in portable applications because of their high energy density, low sensitivity to temperature variations, and no memory effect when recharging. [3] However, they are starting to raise important concerns related to the relatively low abundance of lithium metal-which is likely to increase the environmental impact of its extraction methods-and the large amount of CO 2 generated during battery manufacturing. In fact, its life cycle assessment determines that the use of lithium is only justified in rechargeable applications beyond hundreds of cycles, which clearly prohibits its use as primary batteries. [3,4] Despite all these worrying facts, battery recycling is far from meeting the goals set in developed regions (less than 30% of sold batteries are collected for proper recycling) and it is practically inexistent in low resource settings. [5] The most alarming issue is that consumption of batteries is expected to rise significantly in the following years due to the growth of small-sized portable appliances in the Information and Communications Technology This article presents a new approach for environmentally benign, low-cost batteries intended for single-use applications. The proposed battery is designed and fabricated using exclusively organic materials such as cellulose, carbon, and wax and features an integrated quinone-based redox chemistry to generate electricity within a compact form factor. This primary capillary flow battery is activated by the addition of a liquid sample and has shown continuous operation up to 100 min with an output voltage ...

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.

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Glycerol/bleach flow-through microfluidic fuel cells are presented. Carbon paper-modified Pt/C nanoparticles were used as the anode and cathode. Glycerol oxidation in alkaline medium was tested against hypochlorite reduction in alkaline and acidic media. The mixed media system displayed a power density of 315 mW cm and an open circuit voltage of 1.9-2.0 V.

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