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Overpotential

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


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TL;DR: In this article, molybdenum carbide (β-Mo2C) nanoparticles are prepared by in situ carburization of ammonium molydate on carbon nanotubes and XC-72R carbon black without using any gaseous carbon source.
Abstract: In an attempt to tailor low-cost, precious-metal-free electrocatalysts for water electrolysis in acid, molybdenum carbide (β-Mo2C) nanoparticles are prepared by in situ carburization of ammonium molybdate on carbon nanotubes and XC-72R carbon black without using any gaseous carbon source. The formation of Mo2C is investigated by thermogravimetry and in situ X-ray diffraction. X-ray absorption analysis reveals that Mo2C nanoparticles are inlaid or anchored into the carbon supports, and the electronic modification makes the surface exhibit a relatively moderate Mo–H bond strength. It is found that carbon nanotube-supported Mo2C showed superior electrocatalytic activity and stability in the hydrogen evolution reaction (HER) compared to the bulk Mo2C. An overpotential of 63 mV for driving 1 mA cm−2 of current density was measured for the nanotube-supported Mo2C catalysts; this exceeds the activity of analogous Mo2C catalysts. The enhanced electrochemical activity is facilitated by unique effects of the anchored structure coupled with the electronic modification.

834 citations

Journal ArticleDOI
TL;DR: Experimental and theoretical results demonstrate that lower a coordination number facilitates activation of CO2 to the CO2.- intermediate and hence enhances CO2 electroreduction activity.
Abstract: The design of active, selective, and stable CO2 reduction electrocatalysts is still challenging. A series of atomically dispersed Co catalysts with different nitrogen coordination numbers were prepared and their CO2 electroreduction catalytic performance was explored. The best catalyst, atomically dispersed Co with two-coordinate nitrogen atoms, achieves both high selectivity and superior activity with 94 % CO formation Faradaic efficiency and a current density of 18.1 mA cm-2 at an overpotential of 520 mV. The CO formation turnover frequency reaches a record value of 18 200 h-1 , surpassing most reported metal-based catalysts under comparable conditions. Our experimental and theoretical results demonstrate that lower a coordination number facilitates activation of CO2 to the CO2.- intermediate and hence enhances CO2 electroreduction activity.

834 citations

Journal ArticleDOI
TL;DR: In this paper, a complete polarization model of a solid oxide fuel cell (SOFC) was presented to eliminate the ambiguity of the suitability of such model when used under different design and operating conditions.

830 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the promotional effects of certain transition metal ions on the activity of amorphous MoS3 films and found that Fe, Co, and Ni ions promote the growth of the MoS-3 films, resulting a high surface area and a higher catalyst loading.
Abstract: Molybdenum sulfide materials have been shown as promising non-precious catalysts for hydrogen evolution. This paper describes the study of the promotional effects of certain transition metal ions on the activity of amorphous MoS3 films. Ternary metal sulfide films, M–MoS3 (M = Mn, Fe, Co, Ni, Cu, Zn), have been prepared by cyclic voltammetry of aqueous solutions containing MCl2 and (NH4)2[MoS4]. Whereas the Mn–, Cu–, and Zn–MoS3 films show similar or only slightly higher catalytic activity as the MoS3 film, the Fe–, Co–, and Ni–MoS3 films are significantly more active. The promotional effects of Fe, Co, and Ni ions exist under both acidic and neutral conditions, but the effects are more pronounced under neutral conditions. Up to a 12-fold increase in exchange current density and a 10-fold increase in the current density at an overpotential of 150 mV are observed at pH = 7. It is shown that Fe, Co, and Ni ions promote the growth of the MoS3 films, resulting a high surface area and a higher catalyst loading. These changes are the main contributors to the enhanced activity at pH = 0. However, at pH = 7, Fe, Co, and Ni ions appear to also increase the intrinsic activity of the MoS3 film.

821 citations

Journal ArticleDOI
TL;DR: This is the topotactic fabrication of self-supported Cu3 P nanowire arrays on commercial porous copper foam from its Cu(OH)2 NW/CF precursor by a low-temperature phosphidation reaction.
Abstract: Searching for inexpensive hydrogen evolution reaction (HER) electrocatalysts with high activity has attracted considerable research interest in the past years. Reported herein is the topotactic fabrication of self-supported Cu3P nanowire arrays on commercial porous copper foam (Cu3P NW/CF) from its Cu(OH)(2) NW/CF precursor by a low-temperature phosphidation reaction. Remarkably, as an integrated three-dimensional hydrogen-evolving cathode operating in acidic electrolytes, Cu3P NW/CF maintains its activity for at least 25 hours and exhibits an onset overpotential of 62 mV, a Tafel slope of 67 mVdec(-1), and a Faradaic efficiency close to 100%. Catalytic current density can approach 10 mAcm(-2) at an overpotential of 143 mV.

806 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20232,316
20224,268
20212,838
20202,411
20192,174
20181,740