Overpotential

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

Noncovalent Immobilization of a Molecular Iron-Based Electrocatalyst on Carbon Electrodes for Selective, Efficient CO2-to-CO Conversion in Water

Abstract: Catalysis of fuel-producing reactions can be transferred from homogeneous solution to surface via attachment of the molecular catalyst. A pyrene-appended iron triphenyl porphyrin bearing six pendant OH groups on the phenyl rings in all ortho and ortho′ positions was immobilized on carbon nanotubes via noncovalent interactions and further deposited on glassy carbon. X-ray photoelectron spectroscopy and electrochemistry confirm catalyst immobilization. Using the carbon material, highly selective and rapid catalysis of the reduction of CO2 into CO occurs in water (pH 7.3) with 480 mV overpotential. Catalysis could be sustained for hours without loss of activity and selectivity, and high turnover number was obtained.

Mixed-Node Metal–Organic Frameworks as Efficient Electrocatalysts for Oxygen Evolution Reaction

Abstract: Metal organic frameworks (MOFs), an emerging class of nanoporous crystalline materials, have become increasingly attractive for solar energy applications In this work, we report a newly designed mixed-node MOF catalyst, CoxFe1–x-MOF-74 (0 < x ≤ 1), which acts as a highly efficient electrocatalyst for oxygen evolution reaction (OER) in alkaline solution with remarkably low overpotential (280 mV at a current density of 10 mA/cm2), small Tafel slope (56 mV/dec), and high faradic efficiency (91%) and can deliver a current density of 20 mA/cm2 at 158 V for overall water splitting Moreover, using the combination of multiple spectroscopic methods, including X-ray absorption, electron spin resonance, and X-ray photoelectron spectroscopy, etc, we unraveled the mechanistic origin of the enhanced catalytic performance of CoxFe1–x-MOF-74 compared to its single-metal counterparts We show the mixed-node MOF can provide more open metal sites and an enhanced electron-rich environment, which facilitates efficient cha

Superb Alkaline Hydrogen Evolution and Simultaneous Electricity Generation by Pt‐Decorated Ni3N Nanosheets

Abstract: The development of efficient hydrogen evolution reaction electrocatalysts is critical to the realization of clean hydrogen fuel production, while the sluggish kinetics of the Volmer-step substantially restricts the catalyst performances in alkali electrolyzers, even for noble metal catalysts such as Pt. Here, a Pt-decorated Ni3N nanosheet electrocatalyst is developed to achieve a top performance of hydrogen evolution in alkaline conditions. Possessing a high metallic conductivity and an atomic-thin semiconducting hydroxide surface, the Ni3N nanosheets serve as not only an efficient electron pathway without the hindrance of Schottky barriers, but also provide abundant active sites for water dissociation and generation of hydrogen intermediates, which are further adsorbed on the Pt surface to recombine to H2. The Pt-decorated Ni3N nanosheet catalyst exhibits a hydrogen evolution current density of 200 mA cm−2 at an overpotential of 160 mV versus reversible hydrogen electrode, a Tafel slope of ≈36.5 mV dec−1, and excellent stability of 82.5% current retention after 24 h of operation. Moreover, a hybrid cell consisting of a Pt-decorated Ni3N nanosheet cathode and a Li-metal anode is assembled to achieve simultaneous hydrogen evolution and electricity generation, exhibiting >60 h long-term hydrogen evolution reaction stability and an output voltage ranging from 1.3 to 2.2 V.

Single Atom Ruthenium-Doped CoP/CDs Nanosheets via Splicing of Carbon-Dots for Robust Hydrogen Production

Abstract: Ultrathin two-dimensional catalysts are attracting attention in the field of electrocatalytic hydrogen evolution. This work describe a composite material design in which CoP nanoparticles doped with Ru single-atom sites supported on carbon dots (CDs) single-layer nanosheets formed by splicing CDs (Ru CoP/CDs). Small CD fragments bore abundant functional groups, analogous to pieces of a jigsaw puzzle, and could provide a high density of binding sites to immobilize Ru CoP. The single-particle-thick nanosheets formed by splicing CDs acted as supports, which improved the conductivity of the electrocatalyst and the stability of the catalyst during operation. The Ru CoP/CDs formed from doping atomic Ru dispersed on CoP showed very high efficiency for the hydrogen evolution reaction (HER) over a wide pH range. The catalyst prepared under optimized conditions displayed outstanding stability and activity: the overpotential for the HER at a current density of 10 mA cm was as low as 51 and 49 mV under alkaline and acidic conditions, respectively. Density functional theory calculations showed that the substituted Ru single atoms lowered the proton-coupled electron transfer energy barrier and promoted H−H bond formation, thereby enhancing catalytic performance for the HER. The findings open a new avenue for developing carbon-based hybridization materials with integrated electrocatalytic performance for water splitting. 1 1 1 −2

Nickel Hydroxide as an Active Material for the Positive Electrode in Rechargeable Alkaline Batteries

Abstract: Spherical nickel hydroxide powders coprecipitated with the additives Ca(OH){sub 2}, Co(OH){sub 2}, and Zn(OH){sub 2} were prepared through a spraying technique. These powders, which have a higher tapping density and a much smaller pore volume and crystalline size than conventional powders, were used as the active materials of nickel hydroxide electrodes. The effects of the Ca(OH){sub 2}, Co(OH){sub 2}, and Zn(OH){sub 2} additions on electrode properties such as charge-discharge, reversibility of the electrode reaction, and cycle life, were studied. The relationship between the electrode swelling and the formation of {gamma}-NiOOH was also investigated. The results show that nickel hydroxide powders having a smaller crystallite size show better electrode characteristics such as lower overpotential, higher plateau discharge potential, and higher capacity. The utilization of the active material in the electrodes illustrates that for general use it is better to add Co{sub 2+}, while for a wider temperature range, it would be better to consider the addition of Ca{sup 2+}. The cycle life of the electrode containing Zn{sup 2+} was improved obviously because there was less electrode swelling due to much reduced formation of {gamma}-NiOOH.