overpotential


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overpotential

[¦ō·vər·pə′ten·chəl]
(electricity)
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The voltage decays with the discharge time due to losses caused by mass transport resistance, concentration and activation overpotential, and due to thermodynamics.
Overpotential is necessary as a driving force for charge carrier transport and reactions, thus practical requirement for CO2 conversion is usually greater than the theoretical energy required to produce the desired products [76, 89].
It has been shown previously that BOx demonstrated high electrocatalytic oxygen reduction and low overpotential necessary to catalyze the reaction and a turnover rate of 0.7 [O.sub.2] per Cu x [s.sup.-1], while Pt catalysts turnover rate is three times lower at overpotential of 350 mV [2,10].
Unfortunately, the adsorption of CO on the bare Pt surface in the low potential domain inducts a critical poisoning for the Pt catalyst deactivating most of its active sites and consuming a higher overpotential in undesirable oxidation route.
FeTDHPP was reported to catalyze the C[O.sub.2] reduction to CO, in acidic dimethylformamide (DMF) solutions, with modest overpotential of less than 0.5 V and 90% faradaic yield for CO production through 50 million turnovers over 4 hours (3500 [s.sup.-1]) [77].
It can be seen that Pt/C exhibits superior HER activity in alkaline media with a near-zero onset overpotential, and the conductive acetylene black shows negligible HER activity in the investigated potential range.
Especially for fuel cell applications, EIS is a powerful tool which allows a deep in situ kinetic analysis of catalytic phenomena as well as the separation of different processes contributing to overpotential [25] depending on frequency domain.
Transition metals as dopants in photocatalytic materials have some advantages for the higher N[H.sub.3] yields, such as less charge carrier recombination, stronger photocatalyst absorbance, and lower overpotential for the [N.sub.2] reduction.
The difference between both potentials (E (I) and E (I = 0)) is denominated as polarization or overpotential, measured in volts, [eta] (V).
A significant decrease in the overpotential for NADH oxidation has been achieved using carbon-based nanomaterials.
To achieve sustainable production of [H.sub.2] fuel through water splitting, much effort has been made to design highly efficient electrocatalysts that are vital for lowering the dynamic overpotential during the HER.