Solid electrochemical mass spectrometry (SEMS) for investigation of supported metal catalysts under high vacuum

A new experimental set-up, coupling electrochemistry and mass spectroscopic techniques, for the investigation of a solid electrochemical cell under high vacuum conditions (HV) is presented. Two configurations are realized allowing the investigation of both the electrochemical and electrocatalytical behavior of a thin Pt layer on yttria stabilized zirconia (YSZ). We can readily select the atmosphere down to 10−6 Pa partial pressure and determine the response of the system in less than 1s. Under HV conditions, YSZ appears electrochemically active and we have identified, in the cathodic potential domain, the reduction/oxidation process of zirconia and in the anodic domain, the platinum oxidation/reduction and the oxygen evolution reactions. In a catalytic active gas mixture, despite the Faradaic enhancement of the CO oxidation observed over Pt/YSZ during an anodic polarization, an intriguing sustainable enhanced Pt/YSZ catalyst activity is achieved after current interruptio

Quantum algorithms for optimal effective theory of many-body systems

A common situation in quantum many-body physics is that the underlying theories are known but too complicated to solve efficiently. In such cases, one usually builds simpler effective theories as low-energy or large-scale alternatives to the original theories. Here the central tasks are finding the optimal effective theories among a large number of candidates and proving their equivalence to the original theories. Recently quantum computing has shown the potential of solving quantum many-body systems by exploiting its inherent parallelism. It is thus an interesting topic to discuss the emergence of effective theories and design efficient tools for finding them based on the results from quantum computing. As the first step towards this direction, in this paper, we propose two approaches that apply quantum computing to find the optimal effective theory of a quantum many-body system given its full Hamiltonian. The first algorithm searches the space of effective Hamiltonians by quantum phase estimation and amplitude amplification. The second algorithm is based on a variational approach that is promising for near-future applications.Comment: 8 pages, 4 figure

Investigation of the Pt/YSZ interface at low oxygen partial pressure by solid electrochemical mass spectroscopy under high vacuum conditions

The Pt/YSZ interface was investigated at low oxygen partial pressure under high vacuum (HV) conditions at 400°C. Two different electrochemical techniques were coupled to mass spectrometric gas analysis using a new solid electrochemical mass spectrometric monitoring device. Under cathodic polarization, the lack of oxygen in the gas phase induces the reduction of the YSZ solid electrolyte which acts as oxygen source for the formation of O2− ions migrating to the anode. Under anodic polarization, both platinum oxidation and oxygen evolution reaction are identified. PtOx is formed at both the Pt/YSZ and the Pt/gas interface according to two different mechanisms. At the Pt/YSZ interface, PtOx formation is an electrochemical process following a parabolic growth law, while the presence of PtOx at the Pt/gas interface is related to the diffusion of PtOx formed at the triple phase boundary towards the Pt/gas interface. It is proposed that the side oxygen evolution reaction stabilizes thermodynamically the PtOx diffusion toward the gas exposed interface during the anodic polarizatio

Ferroelectric memristor based on Pt/BiFeO3/Nb-doped SrTiO3 heterostructure

We report a continuously tunable resistive switching behavior in Pt/BiFeO₃/Nb-doped SrTiO₃ heterostructure for ferroelectric memristor application. The resistance of this memristor can be tuned up to 5 × 10⁵% by applying voltage pulses at room temperature, which exhibits excellent retention and anti-fatigue characteristics. The observed memristive behavior is attributed to the modulation effect of the ferroelectric polarization reversal on the width of depletion region and the height of potential barrier of the p-n junction formed at the BiFeO₃/Nb-doped SrTiO₃ interface.This work was supported by the National Natural Science Foundation of China (Grant Nos. 11074193 and 51132001). Q.L. and Y.L. acknowledge the support of the Australian Research Council (ARC) in the form of ARC Discovery Grants

Quantifying electrochemical promotion of induced bipolar Pt particles supported on YSZ

Electrochemical promotion (EP) of CO oxidation is shown for the first time on induced bipolar Pt particles supported on yttria-stabilized zirconia (YSZ). These Pt particles are formed by sputter deposition of high-purity Pt metal followed by sintering. Conditions were chosen to stay below the percolation threshold of Pt particles. In-plane polarization of Pt particles results in a bipolar system and leads to the formation of a large number of galvanic cells partially or completely polarized. We have defined an equivalent number of active cells (n cell) which has been estimated from the oxygen evolution reaction as a function of the applied current on the two feed electrodes. The CO oxidation rate is measured under high vacuum conditions as a function of applied current. The use of isotopically labeled oxygen allows the discrimination of the faradaic process (16O from YSZ) from the non-faradaic process (18O from18O2) and to determine the faradaic efficiency (Λ) and the rate enhancement (ρ) parameters in this bipolar system. These results mark an important step in the realization of electrochemical promotion on highly dispersed catalysts. © 2010

Electrochemical promotion of CO combustion over Pt/YSZ under high vacuum conditions

Electrochemical promotion of CO combustion over Pt/YSZ was investigated under high vacuum conditions. A galvanostatic step was coupled to mass spectrometric gas analysis using an electrochemical mass spectrometric monitoring device. Non-Faradaic electrochemical promotion of catalysis took place at 300 degrees C while only electrochemical oxidation was observed at 400 degrees C. Oxygen evolution measurements revealed that electrochemical promotion is related to the thermodynamically stable PtOx species over the Pt/gas interface. The polarization time and O-2 pressure show strong influence on the relaxation transient upon current interruption. We propose that during anodic polarization, PtOx is first formed at the Pt/YSZ interface. With prolonged polarization time, the formed PtOx either migrates over the Pt/gas interface inducing electrochemical promotion or diffuses into the Pt bulk leading to the oxygen storage. After polarization, the stored O species is released and acts as sacrificial promoter causing the persistent electrochemical promotion effect. (C) 2011 Elsevier B.V. All rights reserved

Current evidence, clinical applications, and future directions of transcranial magnetic stimulation as a treatment for ischemic stroke

Transcranial magnetic stimulation (TMS) is a non-invasive brain neurostimulation technique that can be used as one of the adjunctive treatment techniques for neurological recovery after stroke. Animal studies have shown that TMS treatment of rats with middle cerebral artery occlusion (MCAO) model reduced cerebral infarct volume and improved neurological dysfunction in model rats. In addition, clinical case reports have also shown that TMS treatment has positive neuroprotective effects in stroke patients, improving a variety of post-stroke neurological deficits such as motor function, swallowing, cognitive function, speech function, central post-stroke pain, spasticity, and other post-stroke sequelae. However, even though numerous studies have shown a neuroprotective effect of TMS in stroke patients, its possible neuroprotective mechanism is not clear. Therefore, in this review, we describe the potential mechanisms of TMS to improve neurological function in terms of neurogenesis, angiogenesis, anti-inflammation, antioxidant, and anti-apoptosis, and provide insight into the current clinical application of TMS in multiple neurological dysfunctions in stroke. Finally, some of the current challenges faced by TMS are summarized and some suggestions for its future research directions are made