Topic
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, the authors synthesize coordinatively unsaturated nickel-nitrogen (Ni-N) sites doped within porous carbon with a nickel loading as high as 5.44 wt% by pyrolysis of Zn/Ni bimetallic zeolitic imidazolate framework-8.
Abstract: High Faradaic efficiency and appreciable current density are essential for future applications of the electrochemical CO2 reduction reaction (CO2RR). However, these goals are difficult to achieve simultaneously due to the severe side reaction – the hydrogen evolution reaction (HER). Herein, we successfully synthesized coordinatively unsaturated nickel–nitrogen (Ni–N) sites doped within porous carbon with a nickel loading as high as 5.44 wt% by pyrolysis of Zn/Ni bimetallic zeolitic imidazolate framework-8. Over the Ni–N composite catalysts, the CO current density increases with the overpotential and reaches 71.5 ± 2.9 mA cm−2 at −1.03 V (vs. a reversible hydrogen electrode, RHE), while maintaining a high CO Faradaic efficiency of 92.0–98.0% over a wide potential range of −0.53 to −1.03 V (vs. the RHE). Density functional theory calculations suggest that the CO2RR occurs more easily than the HER over the coordinatively unsaturated Ni–N site. Therefore, highly doped and coordinatively unsaturated Ni–N sites achieve high current density and Faradaic efficiency of the CO2RR simultaneously, breaking current limits in metal–nitrogen composite catalysts.
547 citations
TL;DR: It is proposed that both the high surface area nanostructure and the 2H semiconducting to 1T metallic phase transition of MoS2 are responsible for the outstanding catalytic activity.
Abstract: Molybdenum disulfide (MoS2) with the two-dimensional layered structure has been widely studied as an advanced catalyst for hydrogen evolution reaction (HER). Intercalating guest species into the van der Waals gaps of MoS2 has been demonstrated as an effective approach to tune the electronic structure and consequently improve the HER catalytic activity. In this work, by constructing nanostructured MoS2 particles with largely exposed edge sites on the three-dimensional substrate and subsequently conducting Li electrochemical intercalation and exfoliation processes, an ultrahigh HER performance with 200 mA/cm2 cathodic current density at only 200 mV overpotential is achieved. We propose that both the high surface area nanostructure and the 2H semiconducting to 1T metallic phase transition of MoS2 are responsible for the outstanding catalytic activity. Electrochemical stability test further confirms the long-term operation of the catalyst.
540 citations
TL;DR: This work shows that the modification with a second anion is powerful way to design new catalysts for HER, while remaining good stability in accelerated durability testing.
Abstract: Phosphorus-modified tungsten nitride/reduced graphene oxide (P-WN/rGO) is designed as a high-efficient, low-cost electrocatalyst for the hydrogen evolution reaction (HER). WN (ca. 3 nm in size) on rGO is first synthesized by using the H3[PO4(W3O9)4] cluster as a W source. Followed by phosphorization, the particle size increase slightly to about 4 nm with a P content of 2.52 at %. The interaction of P with rGO and WN results in an obvious increase of work function, being close to Pt metal. The P-WN/rGO exhibits low onset overpotential of 46 mV, Tafel slope of 54 mV dec−1, and a large exchange current density of 0.35 mA cm−2 in acid media. It requires overpotential of only 85 mV at current density of 10 mA cm−2, while remaining good stability in accelerated durability testing. This work shows that the modification with a second anion is powerful way to design new catalysts for HER.
536 citations
TL;DR: In this paper, three categories of non-noble metal electrocatalysts are under heavy investigations: (i) alloys, (ii) transition metal compounds, and (iii) carbonaceous nanomaterials.
532 citations
TL;DR: In this article, the authors investigated the relative stability of different surface terminations of TiO2 interacting with H2O and analyzed the overpotential needed for the electrolysis and photoelectrolysis of water.
Abstract: The oxidation and photo-oxidation of water on the rutile TiO2(110) surface is investigated using density functional theory (DFT) calculations. We investigate the relative stability of different surface terminations of TiO2 interacting with H2O and analyze the overpotential needed for the electrolysis and photoelectrolysis of water. We found that the most difficult step in the splitting of water process is the reaction of a H2O molecule with a vacancy in the surface to form an adsorbed hydroxyl group (OH*). Comparison to experiment shows that the computed overpotential for O2 evolution (0.78 V) is available under the experimental conditions required for both oxygen and hydrogen evolution.
531 citations