Overpotential

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

Component-Controllable WS2(1–x)Se2x Nanotubes for Efficient Hydrogen Evolution Reaction

Abstract: Owing to the excellent potential for fundamental research and technical applications in optoelectronic devices and catalytic activity for hydrogen evolution reaction (HER), transition metal dichalcogenides have recently attracted much attention. Transition metal sulfide nanostructures have been reported and demonstrated promising application in transistors and photodetectors. However, the growth of transition metal selenide nanostructures and their applications has still been a challenge. In this work, we successfully synthesized high-quality WSe2 nanotubes on carbon fibers via selenization. More importantly, through optimizing the growth conditions, ternary WS2(1–x)Se2x nanotubes were synthesized and the composition of S and Se can be systematically controlled. The as-grown WS2(1–x)Se2x nanotubes on carbon fibers, assembled as a working electrode, revealing low overpotential, high exchange current density, and small series resistance, exhibit excellent electrocatalytic properties for hydrogen evolution r...

Selenium-Enriched Nickel Selenide Nanosheets as a Robust Electrocatalyst for Hydrogen Generation

Abstract: To address the urgent need for clean and sustainable energy, the rapid development of hydrogen-based technologies has started to revolutionize the use of earth-abundant noble-metal-free catalysts for the hydrogen evolution reaction (HER). Like the active sites of hydrogenases, the cation sites of pyrite-type transition-metal dichalcogenides have been suggested to be active in the HER. Herein, we synthesized electrodes based on a Se-enriched NiSe2 nanosheet array and explored the relationship between the anion sites and the improved hydrogen evolution activity through theoretical and experimental studies. The free energy for atomic hydrogen adsorption is much lower on the Se sites (0.13 eV) than on the Ni sites (0.87 eV). Notably, this electrode benefits from remarkable kinetic properties, with a small overpotential of 117 mV at 10 mA cm−2, a low Tafel slope of 32 mV per decade, and excellent stability. Control experiments showed that the efficient conversion of H+ into H2 is due to the presence of an excess of selenium in the NiSe2 nanosheet surface.

FeS2 /CoS2 Interface Nanosheets as Efficient Bifunctional Electrocatalyst for Overall Water Splitting.

Abstract: Electrochemical water splitting to produce hydrogen and oxygen, as an important reaction for renewable energy storage, needs highly efficient and stable catalysts. Herein, FeS2 /CoS2 interface nanosheets (NSs) as efficient bifunctional electrocatalysts for overall water splitting are reported. The thickness and interface disordered structure with rich defects of FeS2 /CoS2 NSs are confirmed by atomic force microscopy and high-resolution transmission electron microscopy. Furthermore, extended X-ray absorption fine structure spectroscopy clarifies that FeS2 /CoS2 NSs with sulfur vacancies, which can further increase electrocatalytic performance. Benefiting from the interface nanosheets' structure with abundant defects, the FeS2 /CoS2 NSs show remarkable hydrogen evolution reaction (HER) performance with a low overpotential of 78.2 mV at 10 mA cm-2 and a superior stability for 80 h in 1.0 m KOH, and an overpotential of 302 mV at 100 mA cm-2 for the oxygen evolution reaction (OER). More importantly, the FeS2 /CoS2 NSs display excellent performance for overall water splitting with a voltage of 1.47 V to achieve current density of 10 mA cm-2 and maintain the activity for at least 21 h. The present work highlights the importance of engineering interface nanosheets with rich defects based on transition metal dichalcogenides for boosting the HER and OER performance.

Multielectron, Multistep Molecular Catalysis of Electrochemical Reactions: Benchmarking of Homogeneous Catalysts

Abstract: Current–potential responses in cyclic voltammetry and in preparative-scale electrolysis are established for two-electron two-step homogeneous molecular catalysis after systematic categorization of the various possible reaction schemes. They allow the derivation of catalytic Tafel plots, reflecting the intrinsic properties of the catalysts independent of contingent electrolysis parameters. They serve as a rational basis for benchmarking catalysts of the same electrochemical reaction within the same log(turnover frequency) versus overpotential plane of merit.

Platinum/Carbon nanotube nanocomposite synthesized in supercritical fluid as electrocatalysts for low-temperature fuel cells.

Abstract: Carbon nanotube (CNT)-supported Pt nanoparticle catalysts have been synthesized in supercritical carbon dioxide (scCO2) using platinum(II) acetylacetonate as metal precursor. The structure of the catalysts has been characterized with transmission electron micrograph (TEM) and X-ray photoelectron spectroscopy (XPS). TEM images show that the platinum particles' size is in the range of 5−10 nm. XPS analysis indicates the presence of zero-valence platinum. The Pt−CNT exhibited high catalytic activity both for methanol oxidation and oxygen reduction reaction. The higher catalytic activity has been attributed to the large surface area of carbon nanotubes and the decrease in the overpotential for methanol oxidation and oxygen reduction reaction. Cyclic voltammetric measurements at different scan rates showed that the oxygen reduction reaction at the Pt−CNT electrode is a diffusion-controlled process. Analysis of the electrode kinetics using Tafel plot suggests that Pt−CNT from scCO2 provides a strong electrocata...