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Electrochemistry represents a powerful sustainable method for chemical synthesis; however, its widespread application is limited due to the lack of exposure and appropriate basic training of synthetic chemists and engineers in electrochemistry and electrochemical engineering. The introduction of diverse laboratory practices to the current curricula will improve the understanding of electrochemistry and the theory behind its various applications. Here, we suggest an efficient laboratory experiment on the electrochemical reduction of CO 2 to CO using inexpensive and readily available materials, such as metal wires, plastic vessels, batteries, and a handheld CO detector. Students learn to assemble a divided electrochemical cell and perform important electrochemical reactions, such as electrochemical CO 2 reduction and hydrogen evolution reaction.In this experiment, students analyze the rates of CO production under different electrolysis conditions and learn to understand the effects of operating parameters (applied potential, electrolyte concentration, and nature of the electrode) on the outcome of the reaction. This new comprehensive laboratory experiment is designed for students to better understand basic principles of electrochemistry and is suitable for undergraduate students.

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Silver is a promising electrode material for advanced lithium-based batteries, however it remains relatively unexplored due in part to the complexity of the lithium-silver phase diagram. [1] The larger opportunity is to realize the high capacity of lithium-rich phases with limited volume changes in a lithium-silver foil electrode.[2] ,[3] In order to accomplish this we must first understand the correlation between the equilibrium diagram and dynamic electrochemical phase formation.The lithium-silver equilibrium phase diagram consists of many solid solutions of varying lithium content and capacity. Notable phases (and their approximate compositions and gravimetric capacities based on total mass) are α (Li0-0.5Ag), β (Li1Ag, 230 mAh/g), γ3 (Li2Ag, 450 mAh/g), γ2 (Li4Ag, 800 mAh/g), γ1 (Li9Ag, 1500 mAh/g), and δ (Li50Ag, 3000 mAh/g). Early electrochemical studies of lithium-silver focused on sputter deposited silver films.[4] ,[5] These studies demonstrated the formation of three lithium-silver phases (β, γ3, and γ2) and exhibited poor capacity retention. The effect of deposition conditions (e.g. oxygen incorporation, rapid quenching) on the silver film and its electrochemical behaviour were unclear. More recently, lithium-rich (Li20Ag) composite foils were created by incorporating silver powder in molten lithium and then cooling. The resulting foils were then reversibly cycled between Li20Ag and Li5Ag (reversible capacity of 1600 mAh/g).2 Li20Ag has not been identified as an equilibrium phase but was also not identified as a composite of multiple Li-Ag phases. Each phase identified in the equilibrium diagram exhibited a wide, temperature-dependent composition range. The field needs conclusive identification of lithium-silver phases (including solid solution ranges) as a function of electrochemical conditions for reversible high capacity lithium-silver foil electrodes to be realized.Here we report on the electrochemical lithiation of silver foil using a suite of in-situ and operando methods over a wide range of temperatures and current densities. Two types of pure silver foil (99.99%, ESPI, 25 μm thick; and 99.9%, Shizendo, 2 μm thick) were galvanostatically cycled against lithium metal using Conflat cells[6] and standard electrolytes. Thick foils were used as a pure reference to understand the effects of diffusion; thin foils enabled higher rates and more meaningful x-ray diffraction studies.Potential vs. composition data is provided in Fig. 1a). Results from thick foils are very complicated. In most cases the highest composition observed was approximately Li3Ag. This does not align with a phase boundary in the established equilibrium phase diagram. A solid solution is likely present at intermediate temperatures as a plateau at approximately 10 mV vs. Li/Li+ is apparent. Ex-situ x-ray diffraction of thick lithiated foils (not shown) indicated β and γ3 Li-Ag phases were present on the lithium-facing surface of the electrode. However, the backside of the electrode was nearly pristine Ag. Such discrepancies can be a...

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