Overpotential

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

Directional Construction of Vertical Nitrogen-Doped 1T-2H MoSe2 /Graphene Shell/Core Nanoflake Arrays for Efficient Hydrogen Evolution Reaction.

Abstract: The low utilization of active sites and sluggish reaction kinetics of MoSe2 severely impede its commercial application as electrocatalyst for hydrogen evolution reaction (HER). To address these two issues, the first example of introducing 1T MoSe2 and N dopant into vertical 2H MoSe2/graphene shell/core nanoflake arrays that remarkably boost their HER activity is herein described. By means of the improved conductivity, rich catalytic active sites and highly accessible surface area as a result of the introduction of 1T MoSe2 and N doping as well as the unique structural features, the N-doped 1T-2H MoSe2/graphene (N-MoSe2/VG) shell/core nanoflake arrays show substantially enhanced HER activity. Remarkably, the N-MoSe2/VG nanoflakes exhibit a relatively low onset potential of 45 mV and overpotential of 98 mV (vs RHE) at 10 mA cm−2 with excellent long-term stability (no decay after 20 000 cycles), outperforming most of the recently reported Mo-based electrocatalysts. The success of improving the electrochemical performance via the introduction of 1T phase and N dopant offers new opportunities in the development of high-performance MoSe2-based electrodes for other energy-related applications.

Nickel–Cobalt Diselenide 3D Mesoporous Nanosheet Networks Supported on Ni Foam: An All-pH Highly Efficient Integrated Electrocatalyst for Hydrogen Evolution

Abstract: Novel 3D Ni1−xCoxSe2 mesoporous nanosheet networks with tunable stoichiometry are successfully synthesized on Ni foam (Ni1−xCoxSe2 MNSN/NF with x ranging from 0 to 0.35). The collective effects of special morphological design and electronic structure engineering enable the integrated electrocatalyst to have very high activity for hydrogen evolution reaction (HER) and excellent stability in a wide pH range. Ni0.89Co0.11Se2 MNSN/NF is revealed to exhibit an overpotential (η10) of 85 mV at −10 mA cm−2 in alkaline medium (pH 14) and η10 of 52 mV in acidic solution (pH 0), which are the best among all selenide-based electrocatalysts reported thus far. In particular, it is shown for the first time that the catalyst can work efficiently in neutral solution (pH 7) with a record η10 of 82 mV for all noble metal-free electrocatalysts ever reported. Based on theoretical calculations, it is further verified that the advanced all-pH HER activity of Ni0.89Co0.11Se2 is originated from the enhanced adsorption of both H+ and H2O induced by the substitutional doping of cobalt at an optimal level. It is believed that the present work provides a valuable route for the design and synthesis of inexpensive and efficient all-pH HER electrocatalysts.

Novel porous molybdenum tungsten phosphide hybrid nanosheets on carbon cloth for efficient hydrogen evolution

Abstract: Nanostructural modification and chemical composition tuning are paramount to developing effective non-noble hydrogen evolution reaction (HER) catalysts for water splitting. Herein, we report a novel excellent porous molybdenum tungsten phosphide (Mo–W–P) hybrid nanosheet catalyst for hydrogen evolution, which is synthesized via in situ phosphidation of molybdenum tungsten oxide (Mo–W–O) hybrid nanowires grown on carbon cloth. The three-dimensional (3D) hierarchical hybrid electrocatalyst exhibits impressively high electrocatalytic activity with a low overpotential of 138 mV required to achieve a high current density of 100 mA cm−2 and a small Tafel slope of 52 mV dec−1 in 0.5 M H2SO4, which are significantly higher than those of single MoP nanosheets and WP2 nanorods. Such an outstanding performance of the Mo–W–P hybrid electrocatalyst is attributed to the 3D conductive scaffolds, porous nanosheet structure, and strong synergistic effect of W and Mo atoms in Mo–W–P, making it a very promising catalyst for hydrogen production. Our findings demonstrate that careful control over the morphology and composition of the electrocatalyst can achieve highly efficient hybrid electrocatalysts.

Ultrathin Co3O4 Nanomeshes for the Oxygen Evolution Reaction

Abstract: Ultrathin transition-metal-based nanomeshes can perfectly combine the advantages of two-dimensional (2D) ultrathin nanosheets and porous nanostructures, which have wide applications in energy storage and conversion. In this work, we present an etch-free one-step approach to directly synthesize the ultrathin Co3O4 nanomeshes (Co-UNMs) by employing a CoCl2/K3Co(CN)6 cyanogel as the reaction precursor. The 2D planar structural unit and solid properties of the cyanogel result in the preferential assembly of generated crystal nuclei at the solid–liquid interface (i.e., cyanogel–solution interface) in the 2D direction, which plays a key role in the formation of nanomeshes. The as-prepared Co-UNMs with 1.5 nm thickness and abundant pores have high surface area and numerous defect atoms, resulting in enhanced activity for the oxygen evolution reaction (OER) in alkaline media, such as a low overpotential of 307 mV at 10 mA cm–2, a small Tafel slope of 76 mV dec–1, and attractive durability in 1 M KOH electrolyte.

Communications: Elementary oxygen electrode reactions in the aprotic Li-air battery

Abstract: We discuss the electrochemical reactions at the oxygen electrode of an aprotic Li-air battery. Using density functional theory to estimate the free energy of intermediates during the discharge and charge of the battery, we introduce a reaction free energy diagram and identify possible origins of the overpotential for both processes. We also address the question of electron conductivity through the Li(2)O(2) electrode and show that in the presence of Li vacancies Li(2)O(2) becomes a conductor.