Overpotential

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

A soluble copper–bipyridine water-oxidation electrocatalyst

Abstract: The oxidation of water to O(2) is a key challenge in the production of chemical fuels from electricity. Although several catalysts have been developed for this reaction, substantial challenges remain towards the ultimate goal of an efficient, inexpensive and robust electrocatalyst. Reported here is the first copper-based catalyst for electrolytic water oxidation. Copper-bipyridine-hydroxo complexes rapidly form in situ from simple commercially available copper salts and bipyridine at high pH. Cyclic voltammetry of these solutions at pH 11.8-13.3 shows large, irreversible currents, indicative of catalysis. The production of O(2) is demonstrated both electrochemically and with a fluorescence probe. Catalysis occurs at about 750 mV overpotential. Electrochemical, electron paramagnetic resonance and other studies indicate that the catalyst is a soluble molecular species, that the dominant species in the catalytically active solutions is (2,2'-bipyridine)Cu(OH)(2) and that this is among the most rapid homogeneous water-oxidation catalysts, with a turnover frequency of ~100 s(-1).

Rapid Synthesis of Cobalt Nitride Nanowires: Highly Efficient and Low-Cost Catalysts for Oxygen Evolution.

Abstract: Electrochemical splitting of water to produce hydrogen and oxygen is an important process for many energy storage and conversion devices. Developing efficient, durable, low-cost, and earth-abundant electrocatalysts for the oxygen evolution reaction (OER) is of great urgency. To achieve the rapid synthesis of transition-metal nitride nanostructures and improve their electrocatalytic performance, a new strategy has been developed to convert cobalt oxide precursors into cobalt nitride nanowires through N2 radio frequency plasma treatment. This method requires significantly shorter reaction times (about 1 min) at room temperature compared to conventional high-temperature NH3 annealing which requires a few hours. The plasma treatment significantly enhances the OER activity, as evidenced by a low overpotential of 290 mV to reach a current density of 10 mA cm−2, a small Tafel slope, and long-term durability in an alkaline electrolyte.

Atomically dispersed platinum supported on curved carbon supports for efficient electrocatalytic hydrogen evolution

Abstract: Dispersing catalytically active metals as single atoms on supports represents the ultimate in metal utilization efficiency and is increasingly being used as a strategy to design hydrogen evolution reaction (HER) electrocatalysts. Although platinum (Pt) is highly active for HER, given its high cost it is desirable to find ways to improve performance further while minimizing the Pt loading. Here, we use onion-like nanospheres of carbon (OLC) to anchor stable atomically dispersed Pt to act as a catalyst (Pt1/OLC) for the HER. In acidic media, the performance of the Pt1/OLC catalyst (0.27 wt% Pt) in terms of a low overpotential (38 mV at 10 mA cm−2) and high turnover frequencies (40.78 H2 s−1 at 100 mV) is better than that of a graphene-supported single-atom catalyst with a similar Pt loading, and comparable to a commercial Pt/C catalyst with 20 wt% Pt. First-principle calculations suggest that a tip-enhanced local electric field at the Pt site on the curved support promotes the reaction kinetics for hydrogen evolution. Isolating metal atoms on supports is becoming an increasingly studied approach to design water splitting electrocatalysts. Here, the authors prepare a hydrogen evolution catalyst comprising atomically dispersed Pt atoms on curved carbon supports, which outperform similar catalysts where the support is flat.

Accelerated Hydrogen Evolution Kinetics on NiFe-Layered Double Hydroxide Electrocatalysts by Tailoring Water Dissociation Active Sites.

Abstract: Owing to its earth abundance, low kinetic overpotential, and superior stability, NiFe-layered double hydroxide (NiFe-LDH) has emerged as a promising electrocatalyst for catalyzing water splitting, especially oxygen evolution reaction (OER), in alkaline solutions. Unfortunately, as a result of extremely sluggish water dissociation kinetics (Volmer step), hydrogen evolution reaction (HER) activity of the NiFe-LDH is rather poor in alkaline environment. Here a novel strategy is demonstrated for substantially accelerating the hydrogen evolution kinetics of the NiFe-LDH by partially substituting Fe atoms with Ru. In a 1 m KOH solution, the as-synthesized Ru-doped NiFe-LDH nanosheets (NiFeRu-LDH) exhibit excellent HER performance with an overpotential of 29 mV at 10 mA cm-2 , which is much lower than those of noble metal Pt/C and reported electrocatalysts. Both experimental and theoretical results reveal that the introduction of Ru atoms into NiFe-LDH can efficiently reduce energy barrier of the Volmer step, eventually accelerating its HER kinetics. Benefitting from its outstanding HER activity and remained excellent OER activity, the NiFeRu-LDH steadily drives an alkaline electrolyzer with a current density of 10 mA cm-2 at a cell voltage of 1.52 V, which is much lower than the values for Pt/C-Ir/C couple and state-of-the-art overall water-splitting electrocatalysts.

Mechanism and Kinetics of Li2S Precipitation in Lithium–Sulfur Batteries

Abstract: The kinetics of Li2 S electrodeposition onto carbon in lithium-sulfur batteries are characterized. Electrodeposition is found to be dominated by a 2D nucleation and growth process with rate constants that depend strongly on the electrolyte solvent. Nucleation is found to require a greater overpotential than growth, which results in a morphology that is dependent on the discharge rate.