•CO2RR is studied at Pd100–xCux nanopowders in the form of solid solution alloys.•Focus is set on the acquisition and interpretation of electrochemical signals.•The synergy between Pd and Cu is ...evidenced directly by cyclic voltammetry.•The critical time for full poisoning exhibits a volcano dependence on composition.•Pd70Cu30 is identified as a close to optimal composition in terms of CO tolerance.
A study of the CO2 electrochemical reduction reaction (CO2RR) at Pd100−xCux solid solution type nanoalloys is presented. Cyclic voltammetry and chronoamperometry are used in combination with a cavity microelectrode (CME) for the first time. Low-distorted voltammetric signals obtained with the CME evidence that for alloys with low or moderate Cu content (up to 50 at%) the typical CO2RR inhibition peak, related to CO blocking Pd active sites, becomes a current plateau. Interestingly, the plateau height matches the theoretical value corresponding to the steady state current of a microdisc. This fact indicates a better tolerance of Pd100−xCux towards CO poisoning and also the attainment of a pseudo-steady state where mass transport should be controlled by diffusion. The synergy between Cu and Pd is thus established for the first time at the level of the voltammograms. The chronoamperometric responses exhibit three well defined regions corresponding to (1) double layer charging and diffusion/reaction establishment, (2) beginning of CO poisoning by formation of a CO adlayer and (3) final collapse of the catalytic activity at a critical time, tc, which depends directly on the bimetallic composition. A plot of tc vs. Pd content exhibits a clear volcano shape, from which ~ Pd72Cu28 is identified as a close to optimal composition in terms of CO tolerance and Pd35Cu65 as the composition from which the advantage of alloying Pd with Cu is lost. An in-depth analysis of the I/V response and its evolution with composition and time is performed in the CO2RR and CO stripping regions. As a result, the possibility of developing a method to further increase the catalyst lifetime based on periodical releasing of “CO-like” intermediates by CO stripping is proposed.
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In this study, we demonstrate the benefit of an original vanadium pentoxide (V2O5) nanostructuration on the electrochemical performances. This new synthesis way of high purity nanosized V2O5 consists ...in a facile fluorination reaction of micro-V2O5 in aqueous solution followed by a heat-treatment at low temperature (230°C). Highly porous calisson-like particles with crystallite sizes in the 13–30nm range are obtained. Remarkably, this nanostructured V2O5 exhibits outstanding rate capacities and cycling stabilities. This material can deliver reversible capacities of 260mAhg−1 at 15mAg−1 (C/10 rate) and 150mAhg−1 at 300mAg−1 (2C rate), as well as a stable capacity of 200mAhg−1 at C rate after 50 cycles. The unique structural features of nano-LixV2O5 electrodes are determined over the large Li composition range 0≤x<2 based on XRD and Raman microspectrometry experiments. We provide evidence that lithiation in nanosized V2O5 proceeds via solid solution state without domain boundaries: a single phase behavior of the ε’-type whose interlayer distance and unit cell volume linearly increase with x is revealed. This constitutes a disruption of the usual mirco-LixV2O5 phase diagram made of the successive appearance of the (α/ε), (ε/δ) and (δ/γ) wide biphasic regions. These limited and reversible structural changes combined with shorter Li diffusion pathways explain the huge improvement in electrochemical performances of nano-V2O5. These findings fully elucidate the peculiar voltage profile of nanosized V2O5 and give a unique insight into the impact of nanostructures in terms of electrochemistry and solid state chemistry.
MAX is a complete suite of XAFS data analysis computer programs, written with the cross-platform object scripting langage Livecode 1 working on Windows, MacOSX and Linux systems, freely available on ...our web site since 2007 2. The 2009 version presentation is available in the XAFS14 conference proceedings 3 and regularly updated on the www.xafs.org web site 4.
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•CuPd nanoparticles are synthesized by Metal-Assisted Chemical Etching of Si.•The bimetallic composition is adjusted by the molar ratio of the Cu and Pd salts.•The electronic ...properties (d-band center) vary with the bimetallic composition.•Si etching around nanoparticles is more localized for Pd > PdCu > Cu.•Band bending modeling provides insight into the localized nature of Si etching.
An original study is presented for the synthesis of Cu100-xPdx nanoparticles directly on silicon by Metal Assisted Chemical Etching (MACE). CuPd is chosen as a representative bimetallic system on account of its interest and potential applications in catalysis and electrocatalysis, among others. The proposed methodology allows precise control of the nanoparticle bimetallic composition and structure. Thus, we demonstrate that Cu100-xPdx solid solutions and phase-separated nanoparticles can be synthesized at will by simply changing the deposition conditions. In-depth physical characterization of the synthesized material (structure, morphology, composition, oxidation state and d-band center position) is carried out by XRD, SEM-EDX and XPS. Finally, band bending simulations at the nanoscale in combination with electrochemical measurements help to interpret some of the peculiarities of the Pd, Cu and Cu100-xPdx deposits. The new method can be easily implemented, used for various silicon substrate geometries and extended to any bimetallic system whose metals are suitable for MACE of silicon.
The electrochemical and photoelectrochemical (PEC) properties of undoped, Ni-doped hematite nanoparticles and the film Ni–Fe
2
O
3
/Ni, a photoactive semiconductor, were investigated utilizing a ...methodology that combined the co-precipitation approach, spin-coating method and the sputtering-assisted synthesis of Fe
2
O
3
, Ni–Fe
2
O
3
, and Ni–Fe
2
O
3
/Ni, respectively. The excellent oxygen evolution reaction (OER) response was observed for 15% Ni–Fe
2
O
3
. The super capacitive properties of Ni–Fe
2
O
3
at a scan rate of 10 mVs
−1
show a maximum super capacitance of 914.76 F/g. The electrochemical oxidation of water achieved by Ni–Fe
2
O
3
@GCE modified electrode exhibited the current density of 1.5 mA/cm
2
at 1.5 V vs. the reversible hydrogen electrode (RHE) for 15% of Ni and reveals enhanced specific capacitance of 914.76 F/g. In another part, this work reported the photoelectrochemical (PEC) properties of undoped and 15% Ni–Fe
2
O
3
photoanodes. A photocurrent 1.8 and 0.35 µA/cm
2
at 1.5 V vs. RHE was obtained for undoped and 15% Ni–doped hematite, respectively. It is worth to note that the oxidation current density of 15% Ni–Fe
2
O
3
/Ni reached 300 µA/cm
2
at 1.6 V, which is greater than three times of the highest current density than in water (100 µA/cm
2
).
•Electrochemical Na intercalation in V2O5 was investigated at RT, in a 1M NaClO4/PC electrolyte.•The irreversible formation of NaV2O5 was induced from the first electrochemical discharge ...step.•Electrochemically formed NaV2O5 was found isostructural to the high temperature layered α’-NaV2O5 orthorhombic bronze.•Electrochemically formed NaV2O5 is demonstrated to be a genuine sodium intercalation compound with a high capacity of 120mAhg−1 available near 1.6V at C/10 rate and a promising cycling behaviour.•Zero strain structural behavior was evidenced from X-ray diffraction and Raman spectroscopy during Na+ insertion/extraction in electrochemically formed NaV2O5.
In this work the electrochemical behavior of α-V2O5 at RT, in a 1M NaClO4/PC (propylene carbonate) electrolyte is investigated for the first time. The irreversible formation of a sodiated layered compound is shown from the first electrochemical discharge step. This electrochemically formed compound, with highly stable structure close to that of the high temperature α’-NaV2O5 orthorhombic bronze, is demonstrated to be a genuine sodium intercalation compound. This material exhibits a high capacity of 120mAhg−1 available near 1.6V at C/10 rate with a promising cycling behaviour. X-ray diffraction and Raman spectroscopy show zero strain structural behaviour during Na+ insertion/extraction in this large interlayer spacing material.
In this study, we demonstrate the benefit of an original vanadium pentoxide (V2O5) nanostructuration on the electrochemical performances. This new synthesis way of high purity nanosized V2O5 consists ...in a facile fluorination reaction of micro-V2O5 in aqueous solution followed by a heat-treatment at low temperature (230 °C). Highly porous calisson-like particles with crystallite sizes in the 13–30 nm range are obtained. Remarkably, this nanostructured V2O5 exhibits outstanding rate capacities and cycling stabilities. This material can deliver reversible capacities of 260 mAh g−1 at 15 mA g−1 (C/10 rate) and 150 mAh g−1 at 300 mA g−1 (2C rate), as well as a stable capacity of 200 mAh g−1 at C rate after 50 cycles. The unique structural features of nano-LixV2O5 electrodes are determined over the large Li composition range 0 ≤ x < 2 based on XRD and Raman microspectrometry experiments. We provide evidence that lithiation in nanosized V2O5 proceeds via solid solution state without domain boundaries: a single phase behavior of the ε’-type whose interlayer distance and unit cell volume linearly increase with x is revealed. This constitutes a disruption of the usual mirco-LixV2O5 phase diagram made of the successive appearance of the (α/ε), (ε/δ) and (δ/γ) wide biphasic regions. These limited and reversible structural changes combined with shorter Li diffusion pathways explain the huge improvement in electrochemical performances of nano-V2O5. These findings fully elucidate the peculiar voltage profile of nanosized V2O5 and give a unique insight into the impact of nanostructures in terms of electrochemistry and solid state chemistry.
We characterized the structures in solution of carboplatin and oxaliplatin degradation products in presence of a large excess of methionine (Met). The reaction of carboplatin leads to the formation ...of cis-Pt(Met)2 while, in the case of oxaliplatin, methionine displaces only the oxalate ligand to form Pt(diaminocyclohexane)(Met).
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