Overpotential

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

NiFe (Oxy) Hydroxides Derived from NiFe Disulfides as an Efficient Oxygen Evolution Catalyst for Rechargeable Zn-Air Batteries: The Effect of Surface S Residues.

Abstract: A facile H2 O2 oxidation treatment to tune the properties of metal disulfides for oxygen evolution reaction (OER) activity enhancement is introduced. With this method, the degree of oxidation can be readily controlled and the effect of surface S residues in the resulted metal (oxy)hydroxides for the OER is revealed for the first time. The developed NiFe (oxy)hydroxide catalyst with residual S demonstrates an extraordinarily low OER overpotential of 190 mV at the current density of 10 mA cm-2 after coupling with carbon nanotubes, and outstanding performance in Zn-air battery tests. Theoretical calculation suggests that the surface S residues can significantly reduce the adsorption free energy difference between O* and OH* intermediates on the Fe sites, which should account for the high OER activity of NiFe (oxy)hydroxide catalysts. This work provides significant insight regarding the effect of surface heteroatom residues in OER electrocatalysis and offers a new strategy to design high-performance and cost-efficient OER catalysts.

Three-Dimensional Hierarchical Frameworks Based on MoS2 Nanosheets Self-Assembled on Graphene Oxide for Efficient Electrocatalytic Hydrogen Evolution

Abstract: Advanced materials for electrocatalytic water splitting are central to renewable energy research. In this work, three-dimensional (3D) hierarchical frameworks based on the self-assembly of MoS2 nanosheets on graphene oxide were produced via a simple one-step hydrothermal process. The structures of the resulting 3D frameworks were characterized by using a variety of microscopic and spectroscopic tools, including scanning and transmission electron microscopies, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman scattering. Importantly, the three-dimensional MoS2/graphene frameworks might be used directly as working electrodes which exhibited apparent and stable electrocatalytic activity in hydrogen evolution reaction (HER), as manifested by a large cathodic current density with a small overpotential of −107 mV (−121 mV when loaded on a glassy-carbon electrode) and a Tafel slope of 86.3 mV/dec (46.3 mV/dec when loaded on a glassy-carbon electrode). The remarkable performance might be ascribed to ...

Visible Light-Driven Water Oxidation by a Molecular Ruthenium Catalyst in Homogeneous System

Abstract: Discovery of an efficient catalyst bearing low overpotential toward water oxidation is a key step for light-driven water splitting into dioxygen and dihydrogen. A mononuclear ruthenium complex, Ru(II)L(pic)2 (1) (H2L = 2,2′-bipyridine-6,6′-dicarboxylic acid; pic = 4-picoline), was found capable of oxidizing water eletrochemically at a relatively low potential and promoting light-driven water oxidation using a three-component system composed of a photosensitizer, sacrificial electron acceptor, and complex 1. The detailed electrochemical properties of 1 were studied, and the onset potentials of the electrochemically catalytic curves in pH 7.0 and pH 1.0 solutions are 1.0 and 1.5 V, respectively. The low catalytic potential of 1 under neutral conditions allows the use of [Ru(bpy)3]2+ and even [Ru(dmbpy)3]2+ as a photosensitizer for photochemical water oxidation. Two different sacrificial electron acceptors, [Co(NH3)5Cl]Cl2 and Na2S2O8, were used to generate the oxidized state of ruthenium tris(2,2′-bipyridyl...

Controllable Surface Reorganization Engineering on Cobalt Phosphide Nanowire Arrays for Efficient Alkaline Hydrogen Evolution Reaction.

Abstract: Developing highly efficient hydrogen evolution reaction (HER) catalysts in alkaline media is considered significant and valuable for water splitting. Herein, it is demonstrated that surface reorganization engineering by oxygen plasma engraving on electocatalysts successfully realizes a dramatically enhanced alkaline HER activity. Taking CoP nanowire arrays grown on carbon cloth (denoted as CoP NWs/CC) as an example, the oxygen plasma engraving can trigger moderate CoOx species formation on the surface of the CoP NWs/CC, which is visually verified by the X-ray absorption fine structure, high-resolution transmission electron microscopy, and energy-dispersive spectrometer (EDS) mapping. Benefiting from the moderate CoOx species formed on the surface, which can promote the water dissociation in alkaline HER, the surface reorganization of the CoP NWs/CC realizes almost fourfold enhanced alkaline HER activity and a 180 mV decreased overpotential at 100 mA cm-2 , compared with the pristine ones. More interestingly, this surface reorganization strategy by oxygen plasma engraving can also be effective to other electrocatalysts such as free-standing CoP, Co4 N, O-CoSe2 , and C-CoSe2 nanowires, which verifies the universality of the strategy. This work thus opens up new avenues for designing alkaline HER electrocatalysts based on oxygen plasma engraving.

Nitrogen treatment generates tunable nanohybridization of Ni5P4 nanosheets with nickel hydr(oxy)oxides for efficient hydrogen production in alkaline, seawater and acidic media

Abstract: Hybrid engineering of electrocatalysts is still very challenging for electrochemical water splitting. Ni5P4 is a promising electrocatalyst for hydrogen evolution reaction (HER) but the formation of phosphide-hydrogen on Ni5P4 (P-Hads) bonds usually weakens the HER activity. Herein, we report a simple nitrogen treatment strategy to controllably hybridize Ni5P4 porous nanosheets with amorphous nickel hydr(oxy)oxide [Ni2+δOδ(OH)2−δ] layer and utilize as efficient electrocatalyst for hydrogen evolution reaction (HER) in neutral (real seawater), alkaline and acidic media. The in situ derived Ni5P4@Ni2+δOδ(OH)2−δ hybrid nanosheets can be obtained by annealing the nickel hydroxide-precursor nanosheets coupled with decomposition of NaH2PO2·H2O in nitrogen atmosphere. Benefiting from the thin amorphous Ni2+δOδ(OH)2−δ coated layer, the optimized Ni5P4@Ni2+δOδ(OH)2−δ with 3 nm amorphous layer achieve a current density of 10 mA cm−2 at low overpotential of 87, 144 and 66 mV in alkaline, seawater and acidic media, respectively. Theoretical and experimental analyses show that the hybridization of Ni5P4 and Ni2+δOδ(OH)2−δ could not only serve as protection to further enhance the electrocatalytic properties and high surface area of the hybrid electrocatalyst but also create good electronic interaction and synergistic properties for suppressing P-Hads bonds, which is beneficial for promoting water adsorption and optimizing the free energy of hydrogen adsorption for triggering the catalytic pathway at all pH range. This work offers new insights for facile designing of non-precious transition metal compound hybrids for HER with enhancing electrocatalytic performance and opens a promising pathway for hydrogen production at all-pH range.