Overpotential

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

Influence of particle agglomeration on the catalytic activity of carbon-supported Pt nanoparticles in CO monolayer oxidation

Abstract: Fuel cell electrocatalysts usually feature high noble metal contents, and these favour particle agglomeration. In this paper a variety of synthetic approaches (wet chemical deposition, electrodeposition and electrodeposition on chemically preformed Pt nuclei) is employed to shed light on the influence of nanoparticle agglomeration on their electrocatalytic properties. Pt loading on model glassy carbon (GC) support is increased systematically from 1.8 to 10.6 μg Pt cm−2 and changes in the catalyst structure are followed by transmission electron microscopy. At low metal loadings (≤5.4 μg Pt cm−2) isolated single crystalline Pt nanoparticles are formed on the support surface by wet chemical deposition from H2PtCl4 precursor. An increase in the metal loading results, first, in a systematic increase of the average diameter of isolated Pt nanoparticles and, second, in coalescence of nanoparticles and formation of particle agglomerates. This behaviour is in line with the previous observations on carbon-supported noble metal fuel cell electrocatalysts. The catalytic activity of Pt/GC electrodes is tested in CO monolayer oxidation. In agreement with the previous studies (F. Maillard, M. Eikerling, O. V. Cherstiouk, S. Schreier, E. Savinova and U. Stimming, Faraday Discuss., 2004, 125, 357), we find that the reaction is strongly size sensitive, exhibiting an increase of the reaction overpotential as the particle size decreases below ca. 3 nm. At larger particle sizes the dependence levels off, the catalytic activity of particles with diameters above 3 nm approaching that of polycrystalline Pt. Meanwhile, Pt agglomerates show remarkably enhanced catalytic activity in comparison to either isolated Pt nanopraticles or polycrystalline Pt foil, catalysing CO monolayer oxidation at ca. 90 mV lower overpotential. Enhanced catalytic activity of Pt agglomerates is ascribed to high concentration of surface defects. CO stripping voltammograms from Pt/GC electrodes, comprising Pt agglomerates along with isolated single crystalline Pt nanoparticles from 2 to 6 nm size, feature double voltammetric peaks, the more negative corresponding to CO oxidation on Pt agglomerates, while the more positive to CO oxidation on isolated Pt nanoparticles. It is shown that CO stripping voltammetry provides a fingerprint of the particle size distribution and the extent of particle agglomeration in carbon-supported Pt catalysts.

Strong-Coupled Cobalt Borate Nanosheets/Graphene Hybrid as Electrocatalyst for Water Oxidation Under Both Alkaline and Neutral Conditions

Abstract: Developing highly active catalysts for the oxygen evolution reaction (OER) is of paramount importance for designing various renewable energy storage and conversion devices. Herein, we report the synthesis of a category of Co-Pi analogue, namely cobalt-based borate (Co-Bi) ultrathin nanosheets/graphene hybrid by a room-temperature synthesis approach. Benefiting from the high surface active sites exposure yield, enhanced electron transfer capacity, and strong synergetic coupled effect, this Co-Bi NS/G hybrid shows high catalytic activity with current density of 10 mA cm−2 at overpotential of 290 mV and Tafel slope of 53 mV dec−1 in alkaline medium. Moreover, Co-Bi NS/G electrocatalysts also exhibit promising performance under neutral conditions, with a low onset potential of 235 mV and high current density of 14.4 mA cm−2 at 1.8 V, which is the best OER performance among well-developed Co-based OER electrocatalysts to date. Our finding paves a way to develop highly active OER electrocatalysts.

Highly uniform Ru nanoparticles over N-doped carbon: pH and temperature-universal hydrogen release from water reduction

Abstract: Highly uniform ruthenium (Ru) nanoparticles over N-doped carbon (Ru@CN) was designed and confirmed as a promising candidate for the hydrogen evolution reaction (HER) over a wide pH range In particular, outstanding catalytic activity with an overpotential of 32 mV at 10 mA cm−2 was achieved in basic media Moreover, Ru@CN holds promise for hydrogen production from 0 °C to 60 °C, greatly broadening its applicability

Electrochemical CO2 Reduction to Formic Acid at Low Overpotential and with High Faradaic Efficiency on Carbon-Supported Bimetallic Pd–Pt Nanoparticles

Abstract: The electrochemical reduction of CO2 has attracted significant interest recently, as it is a possible reaction for the storage of renewable energy. Here, we report on the synthesis of PdxPt(100–x)/C nanoparticles and their electrocatalytic properties for the reduction of CO2 to formic acid, compared with their activity for the reverse oxidation of formic acid to CO2. We find that PdxPt(100–x)/C nanoparticles have a very low onset potential for the reduction of CO2 to formic acid of ca. 0 V vs RHE, which approaches the theoretical equilibrium potential of 0.02 V vs RHE for this reaction. Furthermore, the Pd70Pt30/C catalyst shows a faradaic efficiency of 88% toward formic acid after 1 h of electrolysis at −0.4 V vs RHE with an average current density of ∼5 mA/cm2. Therefore, this catalyst shows a competing or even better faradaic efficiency toward formic acid compared to recently reported catalysts, at a substantially lower overpotential, while avoiding a strong deactivation that was observed with previous...

Under-Water Superaerophobic Pine-Shaped Pt Nanoarray Electrode for Ultrahigh-Performance Hydrogen Evolution

Abstract: A pine-shaped Pt nanostructured electrode with under-water superaerophobicity for ultrahigh and steady hydrogen evolution reaction (HER) performance is successfully fabricated by a facile and easily scalable electro-deposition technique. Due to the lower bubble adhesive force (11.5 +/- 1.2 mu N), the higher bubble contact angle (161.3 degrees +/- 3.4 degrees) in aqueous solution, and the smaller size of bubbles release for pine-shaped Pt nanostructured electrode, the incomparable under-water superaerophobicity for final repellence of bubbles from submerged surface with ease, is successfully achieved, compared to that for nanosphere electrode and for Pt flat electrode. With the merits of superior under-water superaerophobicity and excellent nanoarray morphology, pine-shaped Pt nanostructured electrode with the ultrahigh electrocatalytic HER performance, excellent durability, no obvious current fluctuation, and dramatically fast current density increase at overpotential range (3.85 mA mV(-1), 2.55 and 13.75 times higher than that for nanosphere electrode and for Pt flat electrode, respectively), is obtained, much superior to Pt nanosphere and flat electrodes. The successful introduction of under-water superaerophobicity to in-time repel as-formed H-2 bubbles may open up a new pathway for designing more efficient electrocatalysts with potentially practical utilization in the near future.