Overpotential

About: Overpotential is a research topic. Over the lifetime, 16474 publications have been published within this topic receiving 616632 citations.

Ultrathin two-dimensional cobalt–organic framework nanosheets for high-performance electrocatalytic oxygen evolution

Abstract: Ultrathin two-dimensional cobalt–organic framework (Co–MOF) nanosheets [Co2(OH)2BDC, BDC = 1,4-benzenedicarboxylate] with good catalytic activity for the oxygen evolution reaction were synthesized by a simple surfactant-assisted hydrothermal method. The resulting material shows a low overpotential of 263 mV at 10 mA cm−2 and a Tafel slope of 74 mV dec−1 in 1.0 M KOH. The morphology and properties of the material before and after electrocatalysis did not change significantly over a long period of time and it maintained electrochemical stability for 12 000 s. The unsaturated CoII active center on the surface of the ultrathin two-dimensional cobalt–organic framework nanosheets enhances their oxygen evolution reaction performance. These results are significantly superior to most of the previously reported transition metal–organic framework or metal oxide electrocatalysts. We believe that the ultrathin two-dimensional metal–organic framework nanosheets synthesized by this simple process will be widely used in future energy conversion devices.

Voltammetry of Redox-Active Groups Irreversibly Adsorbed onto Electrodes. Treatment Using the Marcus Relation between Rate and Overpotential

Abstract: A treatment of linear sweep voltammetry for redox-active groups irreversibly immobilized on electrodes is presented with use of the Marcus theory of electrode kinetics to relate rate constants to overpotential. The present treatment extends an earlier treatment of the same problem (Laviron, E. J. Electroanal. Chem. 1979, 101, 19) that used the Butler-Volmer theory to relate rate coastants to overpotential. The behavior predicted in the present treatment matches that of the earlier treatment for very high reorginzation energies; however, for reorganization energies below about 2.0 eV, voltammograms are predicted to be broader and peak potentials are in most cases predicted to shift further from E o' than in the earlier treatment. These effects are most pronounced at high overpotentials and at high sweep rates

Metal-organic framework derived Co3O4/MoS2 heterostructure for efficient bifunctional electrocatalysts for oxygen evolution reaction and hydrogen evolution reaction

Abstract: Fabrication of highly efficient, sustainable and low-cost nonprecious metal oxide for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is exceedingly challenging and warranted for overall water splitting. Herein, we synthesized cobalt nanoleaves metal-organic framed work (MOF) on nickel foam substrate with uniform growth. After calcination of Co-MOF, molybdenum disulfide nanosheets is grown by a facial hydrothermal method. The as-prepared heterostructure (Co3O4/MoS2) can act as bifunctional electrocatalysts for overall water splitting. Under optimized condition, synthesized Co3O4/MoS2 heterostructure catalyst exhibited excellent catalytic activity for both OER and HER in 1 M KOH solution with a current density of 20 mA cm−2 at overpotential of 230 mV for OER and 205 mV for HER (@ j = 10 mA cm−2) and Tafel slopes of 45 and 98 mV dec-1, respectively. The superior catalytic activity for both OER and HER arises from the unique heterostructure of Co3O4/MoS2 and the synergistic effects of Co3O4 and MoS2.

Electrochemical Carbon Monoxide Reduction on Polycrystalline Copper: Effects of Potential, Pressure, and pH on Selectivity toward Multicarbon and Oxygenated Products

Abstract: Understanding the surface reactivity of CO, which is a key intermediate during electrochemical CO2 reduction, is crucial for the development of catalysts that selectively target desired products for the conversion of CO2 to fuels and chemicals In this study, a custom-designed electrochemical cell is utilized to investigate planar polycrystalline copper as an electrocatalyst for CO reduction under alkaline conditions Seven major CO reduction products have been observed including various hydrocarbons and oxygenates which are also common CO2 reduction products, strongly indicating that CO is a key reaction intermediate for these further-reduced products A comparison of CO and CO2 reduction demonstrates that there is a large decrease in the overpotential for C–C coupled products under CO reduction conditions The effects of CO partial pressure and electrolyte pH are investigated; we conclude that the aforementioned large potential shift is primarily a pH effect Thus, alkaline conditions can be used to inc

Pulse-Electrodeposited Ni–Fe (Oxy)hydroxide Oxygen Evolution Electrocatalysts with High Geometric and Intrinsic Activities at Large Mass Loadings

Abstract: One practical metric for electrocatalyst performance is current per geometric area at a given applied overpotential. An obvious route to increase performance is to increase the catalyst mass loading—as long as the intrinsic performance (i.e., specific activity or turnover frequency) of the catalyst is independent of loading, and other electrical, ionic, or mass-transfer resistances are not severe. Here we report the geometric and intrinsic oxygen evolution reaction (OER) activities of Ni(Fe)OOH films, the fastest known water oxidation catalyst in basic media, as a function of mass loading from 0 to ∼100 μg cm–2. We discuss practices for measuring and reporting intrinsic activities, highlighting experimental conditions where the film activity on a per-metal-cation basis can be accurately measured and where capacitance measurements of electrochemically active surface area fail. We find that the electrochemical reversibility of the (nominally) Ni2+/3+ redox wave correlates with the apparent intrinsic activit...