A highly efficient recyclable system for capture and subsequent conversion of CO 2 to formate salts is reported that utilizes aqueous inorganic hydroxide solutions for CO 2 capture along with homogeneous pincer catalysts for hydrogenation. The produced aqueous solutions of formate salts are directly utilized, without any purification, in a direct formate fuel cell to produce electricity and regenerate the hydroxide base, achieving an overall carbon-neutral cycle. The catalysts and organic solvent are recycled by employing a biphasic solvent system (2-MTHF/H 2 O) with no significant decrease in turnover frequency (TOF) over five cycles. Among different hydroxides, NaOH and KOH performed best in tandem CO 2 capture and conversion due to their rapid rate of capture, high formate conversion yield, and high catalytic TOF to their corresponding formate salts. Among various catalysts, Ru-and Fe-based PNP complexes were the most active for hydrogenation. The extremely low vapor pressure, nontoxic nature, easy regenerability, and high reactivity of NaOH/KOH toward CO 2 make them ideal for scrubbing CO 2 even from lowconcentration sourcessuch as ambient airand converting it to value-added products.

We describe the first direct formate fuel cell on a paper microfluidic platform. In traditional membrane-less microfluidic fuel cells (MFCs), external pumping consumes power produced by the fuel cell in order to maintain co-laminar flow of the anode stream and oxidant stream to prevent mixing. However, in paper microfluidics, capillary action drives flow while minimizing stream mixing. In this work, we demonstrate a paper MFC that uses formate and hydrogen peroxide as the anode fuel and cathode oxidant, respectively. Using these materials we achieve a maximum power density of nearly 2.5 mW/mg Pd. In a series configuration, our MFC achieves an open circuit voltage just over 1 V, and in a parallel configuration, short circuit of 20 mA absolute current. We also demonstrate that the MFC does not require continuous flow of fuel and oxidant to produce power. We found that we can pre-saturate the materials on the paper, stop the electrolyte flow, and still produce approximately 0.5 V for 15 min. This type of paper MFC has potential applications in point-of-care diagnostic devices and other electrochemical sensors.

Paper-based microfluidic fuel cells (MFCs) are a potential replacement for traditional FCs and batteries due to their low cost, portability, and simplicity to operate. In MFCs, separate solutions of fuel and oxidant migrate through paper due to capillary action and laminar flow and, upon contact with each other and catalyst, produce electricity. In the present work, we describe an improved microfluidic paper-based direct formate FC (DFFC) employing formate and hydrogen peroxide as the anode fuel and cathode oxidant, respectively. The dimensions of the lateral column, current collectors, and cathode were optimized. A maximum power density of 2.53 mW/cm(2) was achieved with a DFFC of surface area 3.0 cm(2) , steel mesh as current collector, 5% carbon to paint mass ratio for cathode electrode and, 30% hydrogen peroxide. The longevity of the MFC's detailed herein is greater than eight hours with continuous flow of streams. In a series configuration, the MFCs generate sufficient energy to power light-emitting diodes and a handheld calculator.

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The development of alkaline anion exchange membranes (AEM) has allowed for a myriad of new liquid fuels to be used in fuel cell applications that cannot be effectively oxidized under acidic conditions using proton exchange membrane fuel cells (PEMFCs). Moreover, many of these fuels are readily electrooxidized by non-platinum group metal catalysts under basic conditions. Interested in the direct formate fuel cell (DFFC), we have explored the activity of palladium supported on reduced graphene oxide (Pd/rGO) toward the formate oxidation reaction in the alkaline medium. The reduction of GO to rGO and synthesis of Pd nanoparticles were confirmed using X-ray diffraction, Raman, and X-ray photoelectron spectroscopies. The surface morphology was evaluated by scanning electron microscopy and transmission electron microscopy. Half-cell studies demonstrated superior electrocatalytic activity and stability toward formate electrooxidation for Pd/rGO than commercial Pd/C catalysts. A low metal loading AEM DFFC, fabricated with a Pd/rGO anode catalyst, displayed a 15% increase in maximum power density at 60 °C compared to the commercial Pd/C catalyst.