Figure. A lemon battery is a basic 2-electrode electrochemical cell. The nail (zinc) is the negative electrode (anode), the penny (copper) is the positive electrode (cathode) and the lemon juice is the electrolyte.
Electrochemical reactions form the backbone of a wide variety of energy technologies including batteries, fuel cells, and electrolyzers. An electrochemical reaction is when an electron is passed from a semiconductor or metal electrode into an electrolyte solution, causing a chemical reaction. In most electrochemical cells, the electrolyte is oxidized (loses and electron) at one electrode and reduced (gains an electron) at another electrode. The two electrodes are then connected to complete the electric circuit. Between the two electrodes can be a load (light bulb, TV, etc.), in the case of a battery, or a power source, in the case of an electrolyzer.
A specific branch of electrochemistry that is of particular interest in the Kamat lab is photoelectrochemistry. A photoelectrochemical cell is an electrochemical cell where one or both of the electrodes absorbs light, as in a Quantum Dot Solar Cell (QDSC). In a photoelectrochemical cell, the absorbed photon provides the energy which drives the reduction/oxidation of the electrolyte and forces electricity through the load. Careful tuning of the rates of the individual electrochemical reactions and electron transfer processes through the electrode, is one of the main ways in which the overall device efficiency can be optimized.
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Our Research Focus
Figure. MnO2/RGO composites show improved Li-ion battery performance. The reason for the improvement was attributed to better electrode kinetics, more rapid diffusion of Li+ to intercalation sites, and a greater capacitance effect during discharge.
- Understanding the electrochemical reactions present in Quantum Dot Solar Cells and controlling the rates of undesirable reactions
- Increasing electrochemical reaction rates through the design of nanostructured catalyst systems
- Developing improved Li-ion batteries through better understanding of their electrochemical reactions
Figure. Cu2S/RGO composite developed for use as a counter electrode for quantum dot solar cells employing a sulfide/polysulfide redox couple.
- Demonstrated the efficient regeneration of the S2-/Sn2 electrolyte in QDSCs using a Cu2S/RGO counter electrode
- Elucidated the role of the catalyst, IrO, in the photo-oxidation of water using TiO2
- Mapped the kinetics of hole regeneration, and chemical species present in a CdSe QDSC employing the S2-/Sn2 redox couple
425. Origin of Reduced Graphene Oxide Enhancements in Electrochemical Energy Storage. Radich, J. G.; Kamat, P. V. ACS Catal. 2012, 2, 807–816.
422. Boosting the Efficiency of Quantum Dot Sensitized Solar Cells Through Modulation of Interfacial Charge Transfer. Kamat, P. V. Acc. Chem. Res. 2012, ASAP.
416. Cu2S -Reduced Graphene Oxide Composite for High Efficiency Quantum Dot Solar Cells . Overcoming the Redox Limitations of S2-/Sn2- at the Counter Electrode Radich, J. G.; Dwyer, R.; Kamat, P. V. J. Phys. Chem. Lett. 2011, 2, 2453–2460.
415. Role of Water Oxidation Catalyst, IrO2 in Shuttling Photogenerated Holes Across TiO2 Interface Meekins, B. H.; Kamat, P. V., J. Phys. Chem. Lett. 2011, 2, 2304-2310.
411. CdSe Quantum Dot-Fullerene Hybrid Nanocomposite for Solar Energy Conversion: Electron Transfer and Photoelectrochemistry Bang, J. H.; Kamat, P. V. ACS Nano 2011, 5 (12), pp 9421–9427.
409. Understanding the Role of the Sulfide Redox Couple (S2-/Sn2-) in Quantum Dot Sensitized Solar Cells Chakrapani, V.; Baker, D.; Kamat, P. V. J. Am. Chem. Soc. 2011, 133, 9607-9615.
407. Graphene-based Composites for Electrochemical Energy Storage Radich, J. G.; McGinn, P. J.; Kamat, P. V. Interface 2011, Spring Issue, 63-66.
400. Beyond photovoltaics: semiconductor nanoarchitectures for liquid junction solar cells Kamat, P. V.; Tvrdy, K.; Baker, D. R.; Radich, J. G. Chem. Rev. 2010, 110, 6664–6688.
386. Got TiO2 Nanotubes? Lithium Ion Intercalation can Boost Their Photoelectrochemical Performance Three-Fold Meekins, B. H.; Kamat, P. V. ACS Nano 2009, 3, 3437–3446. NDRL 4821
385. Fuel Cell Geared in Reverse. Photocatalytic Hydrogen Production using a TiO2/Nafion/Pt Membrane Assembly with No Applied Bias Seger, B.; Kamat, P. V. J. Phys. Chem. C 2009, 113,18946–18952. NDRL 4820