Overpotential

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

Self-supported nanoporous NiCo2O4 nanowires with cobalt–nickel layered oxide nanosheets for overall water splitting

Abstract: Water splitting via the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in producing H2 and O2 is a very important process in the energy field. Developing an efficient catalyst which can be applied to both HER and OER is crucial. Here, a bifunctional catalyst, CFP/NiCo2O4/Co0.57Ni0.43LMOs, has been successfully fabricated. It exhibits remarkable performance for OER in 0.1 M KOH producing a current density of 10 mA cm−2 at an overpotential of 0.34 V (1.57 V vs. RHE), better than that of the commercial Ir/C (20%) catalyst. Simultaneously, it also exhibits good catalytic performance for HER in 0.5 M H2SO4 producing a current density of 10 mA cm−2 at an overpotential of 52 mV and a Tafel slope of 34 mV dec−1, approaching that of the commercial Pt/C (20%) nanocatalyst. Particularly, CFP/NiCo2O4/Co0.57Ni0.43LMOs present better durability under harsh OER and HER cycling conditions than commercial Ir/C and Pt/C. Furthermore, an H-type electrolyzer was fabricated by applying CFP/NiCo2O4/Co0.57Ni0.43LMOs as the cathode and anode electrocatalyst, which can be driven by a single-cell battery. This bifunctional catalyst will be very promising in overall water splitting.

Model for the Particle Size, Overpotential, and Strain Dependence of Phase Transition Pathways in Storage Electrodes: Application to Nanoscale Olivines

Abstract: In the drive toward improved electrical energy storage for applications ranging from wireless devices to electric vehicles to grid stabilization, nanoscale materials are of growing interest as ion storage electrodes. Nanoscale olivines based on LiMPO4 (M = Fe, Mn, Co, Ni) are one class of compounds for which recent experimental developments reveal very different phase transition and solid-solubility behavior compared to larger particles. The olivines may be an exemplar for generalized behavior for which metastable crystalline or amorphous phases are produced under the large driving forces incurred during electrochemical reactions. Here we use a diffuse-interface thermodynamic model to assess the conditions under which amorphous phase transitions may occur in nanoscale LiMPO4 particles. There are three central conclusions. First, assuming as with similar solids that the amorphous phase has the lower surface energy, it is found that an initially crystalline phase may undergo amorphization during cycling whe...

An amorphous Co-carbonate-hydroxide nanowire array for efficient and durable oxygen evolution reaction in carbonate electrolytes

Abstract: The development of earth-abundant catalysts toward high-efficient and durable oxygen evolution reaction (OER) electrocatalysis in the carbonate electrolyte is in great demand but remains a huge challenge. In this communication, we describe the development of a Co-carbonate-hydroxide nanowire array on nickel foam (CoCH/NF) via in situ electrochemical conversion of the Co(CO3)0.5(OH)·0.11H2O nanowire array. When utilized as a 3D catalyst electrode for the OER in 1.0 M KHCO3 (pH: 8.3), as-formed CoCH/NF demands overpotential of only 332 mV to drive a geometrical catalytic current density of 10 mA cm-2, with its catalytic activity being maintained for at least 130 h. Impressively, it also demonstrates a high turnover frequency value of 0.22 mol O2 s-1 at an overpotential of 500 mV.

Nickel oxide functionalized silicon for efficient photo-oxidation of water

Abstract: We report a nickel oxide (NiOx) thin film, from a cost-effective sol–gel process, coated n-type silicon (n-Si) as a photoanode for efficient photo-oxidation of water under neutral pH condition. The NiOx thin film has three functions: (i) serves as a protection layer to improve the chemical stability of the Si photoelectrode, (ii) acts as an oxygen evolution catalyst, and (iii) provides junction photovoltage to further reduce overpotential. The oxygen evolution onset potential is reduced to below the thermodynamic water oxidation level and oxygen evolution was observed at low overpotentials. Our results demonstrate the fabrication of robust photoelectrodes from low-cost NiOx and Si, which enable a practical solar water oxidation with high efficiency.

Iron-doped nickel disulfide nanoarray: A highly efficient and stable electrocatalyst for water splitting

Abstract: Developing efficient water-splitting electrocatalysts, particularly for the anodic oxygen evolution reaction (OER), is an important challenge in energy conversion technologies. In this study, we report the development of iron-doped nickel disulfide nanoarray on Ti mesh (Fe0.1-NiS2 NA/Ti) via the sulfidation of its nickel–iron-layered double hydroxide precursor (NiFe-LDH NA/Ti). As a three-dimensional OER anode, Fe0.1-NiS2 NA/Ti exhibits remarkable activity and stability in 1.0 M KOH, with the requirement of a low overpotential of 231 mV to achieve 100 mA·cm−2. In addition, it exhibits excellent activity and durability in 30 wt.% KOH. Notably, this electrode is also efficient for the cathodic hydrogen evolution reaction under alkaline conditions.