Overpotential

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

Hierarchical Hollow Nanoprisms Based on Ultrathin Ni-Fe Layered Double Hydroxide Nanosheets with Enhanced Electrocatalytic Activity towards Oxygen Evolution

Abstract: The oxygen evolution reaction (OER) is involved in various renewable energy systems, such as water-splitting cells and metal-air batteries. Ni-Fe layered double hydroxides (LDHs) have been reported as promising OER electrocatalysts in alkaline electrolytes. The rational design of advanced nanostructures for Ni-Fe LDHs is highly desirable to optimize their electrocatalytic performance. Herein, we report a facile self-templated strategy for the synthesis of novel hierarchical hollow nanoprisms composed of ultrathin Ni-Fe LDH nanosheets. Tetragonal nanoprisms of nickel precursors were first synthesized as the self-sacrificing template. Afterwards, these Ni precursors were consumed during the hydrolysis of iron(II) sulfate for the simultaneous growth of a layer of Ni-Fe LDH nanosheets on the surface. The resultant Ni-Fe LDH hollow prisms with large surface areas manifest high electrocatalytic activity towards the OER with low overpotential, small Tafel slope, and remarkable stability.

Amorphous FeOOH Oxygen Evolution Reaction Catalyst for Photoelectrochemical Water Splitting

Abstract: Reaching the goal of economical photoelectrochemical (PEC) water splitting will likely require the combination of efficient solar absorbers with high activity electrocatalysts for the hydrogen and oxygen evolution reactions (HER and OER). Toward this goal, we synthesized an amorphous FeOOH (a-FeOOH) phase that has not previously been studied as an OER catalyst. The a-FeOOH films show activity comparable to that of another OER cocatalyst, Co-borate (Co–Bi), in 1 M Na2CO3, reaching 10 mA/cm2 at an overpotential of ∼550 mV for 10 nm thick films. Additionally, the a-FeOOH thin films absorb less than 3% of the solar photons (AM1.5G) with energy greater than 1.9 eV, are homogeneous over large areas, and act as a protective layer separating the solution from the solar absorber. The utility of a-FeOOH in a realistic system is tested by depositing on amorphous Si triple junction solar cells with a photovoltaic efficiency of 6.8%. The resulting a-FeOOH/a-Si devices achieve a total water splitting efficiency of 4.3%...

Phosphorus-Doped Co3O4 Nanowire Array: A Highly Efficient Bifunctional Electrocatalyst for Overall Water Splitting

Abstract: It is vitally essential to design highly efficient and cost-effective bifunctional electrocatalysts toward water splitting. Herein, we report the development of P-doped Co3O4 nanowire array on nickel foam (P-Co3O4/NF) from Co3O4 nanowire array through low-temperature annealing, using NaH2PO2 as the P source. As a 3D catalyst, such P-Co3O4/NF demonstrates superior performance for oxygen evolution reaction with a low overpotential (260 mV at 20 mA cm–2), a small Tafel slope (60 mV dec–1), and a satisfying durability in 1.0 M KOH. Density functional theory calculations indicate that P-Co3O4 has a reaction free-energy value that is much smaller than that of pristine Co3O4 for the potential determining step of the oxygen evolution reaction. Such P-Co3O4/NF also performs efficiently for hydrogen evolution reaction, and a two-electrode alkaline electrolyzer assembled by P8.6-Co3O4/NF as both anode and cathode needs only 1.63 V to reach a water-splitting current of 10 mA cm–2.

Ultrafine Silver Nanoparticles for Seeded Lithium Deposition toward Stable Lithium Metal Anode

Abstract: To exploit the high energy density of the lithium (Li) metal battery, it is imperative to address the dendrite growth and interface instability of the anode. 3D hosts for Li metal are expected to suppress the growth of Li dendrites. Heterogeneous seeds are effective in guiding Li deposition and realizing spatial control over Li nucleation. Herein, this study shows that ultrafine silver (Ag) nanoparticles, which are synthesized via a novel rapid Joule heating method, can serve as nanoseeds to direct the deposition of Li within the 3D host materials, resolving the problems of the Li metal anode. By optimizing the Joule heating method, ultrafine Ag nanoparticles (≈40 nm) are homogeneously anchored on carbon nanofibers. The Ag nanoseeds effectively reduce the nucleation overpotential of Li and guide the Li deposition in the 3D carbon matrix uniformly, free from the dendrites. A stable and reversible Li metal anode is achieved in virtue of the Ag nanoseeds in the 3D substrate, showing a low overpotential (≈0.025 V) for a long cycle life. The ultrafine nanoseeds achieved by rapid Joule heating render uniform deposition of Li metal anode in 3D hosts, promising a safe and long-life Li metal battery for high-energy applications.

Shape-Dependent Electrocatalytic Reduction of CO2 to CO on Triangular Silver Nanoplates.

Abstract: Electrochemical reduction of CO2 (CO2RR) provides great potential for intermittent renewable energy storage. This study demonstrates a predominant shape-dependent electrocatalytic reduction of CO2 to CO on triangular silver nanoplates (Tri-Ag-NPs) in 0.1 M KHCO3. Compared with similarly sized Ag nanoparticles (SS-Ag-NPs) and bulk Ag, Tri-Ag-NPs exhibited an enhanced current density and significantly improved Faradaic efficiency (96.8%) and energy efficiency (61.7%), together with a considerable durability (7 days). Additionally, CO starts to be observed at an ultralow overpotential of 96 mV, further confirming the superiority of Tri-Ag-NPs as a catalyst for CO2RR toward CO formation. Density functional theory calculations reveal that the significantly enhanced electrocatalytic activity and selectivity at lowered overpotential originate from the shape-controlled structure. This not only provides the optimum edge-to-corner ratio but also dominates at the facet of Ag(100) where it requires lower energy to in...