SnS is increasingly studied due to its various domains of applications and especially in renewable energy. This work focused on the understanding of the electrochemical behavior of SnS from a bath containing pyrophosphates (PP). PP were used to stabilize the precursor of Sn(II) in solution. First, Sn-PP and thiosulfate, used as a sulfur precursor, electrochemical system were studied separately. Sn-PP system appears quite complex with multiple redox reactions related to the Sn-PP complex but also PP which are electroactives and the formation/oxidation of AuSn. Voltammetries clearly show the advantage of using PP as stabilizing agent for Sn. Regarding thiosulfate, special attention must be paid to the preparation of the solution in order to obtain colloidal sulfur. Afterwards, the study of the electrochemical system allows the assignments of the redox reactions. Then, the binary system was studied through voltammetry and electrodeposition. The deposits were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Two major parameters were studied namely, the ratio S/Sn precursors in solution and the potential of deposition. Single-phase, well-crystallized and oriented SnS films were obtained for a ratio of S/Sn of 4.2 and at -0.7 V vs Ag/AgCl.

This study describes a reproducible process for forming highly mesoporous, mechanically robust, and handleable aerogels based on entangled poly(3-hexylthiophene) (P3HT) and syndiotactic polystyrene (sPS) nanofibers for thermoelectric applications. The highly porous structure results in low thermal conductivity, allowing the temperature difference (between the hot and the cold side) to be maintained across the aerogel sample. Porosity also enables dopants to diffuse efficiently within the sample. When using 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4TCNQ), the highest dopant uptake leads to a maximum apparent electrical conductivity of 2 x 10-2 S cm-1 and a Seebeck coefficient (58 mu V K-1) close to the values obtained in thin films. The Seebeck coefficient is not affected by the high porosity of the material. To improve the doping level of the P3HT:sPS aerogels, FeCl3 or a mixture of F4TCNQ:FeCl3 is also used as a dopant. This enhances the power factor (0.2 mu W m-1 K-2) without significantly increasing the thermal conductivity (30-40 mW m-1 K-1). Finally, the use of the doped aerogel as a vertical thermoelectric generator with one leg is demonstrated by generating a few tens of nW at a thermal difference of 11 K. This result highlights the potential for integrating these polymer aerogels into wearable thermoelectric generators for powering microelectronics.

A sandwich structure of TiO2 layer was proposed, i.e., a dense inner layer and a porous outer layer, for anodising of technical titanium in a DES solvent composed of choline dihydrogencitrate and oxalic acid in a 1:1 M ratio. The first seconds of logarithm growth of thickness from a single nm to about 10 nm formed a barrier inner layer with resistance of 28 M Omega cm(2), low electric capacitance (15 mu F cm(-2)) and not so high outer layer resistance (similar to 0.6 M Omega cm(2)). It was accompanied by a distinct decrease in anodic current density in the passive range in 0.05 mol dm(-3) NaCl solution. Extension of the anodising time from 10 s to 20 min, despite the fact that the layer thickness increased from about 10 to over 30 nm, did not deepen this initial trend due to the possible development amorphous features more similar to titanium(IV) hydroxide than to titanium(IV) oxide.

The deposition of functional coatings by Physical Vapor Deposition (PVD) on open-cell 3D foams represents a burgeoning area within material science, especially for electrochemical applications. Due to the novelty of this field and the unique geometry of the foams, the use of PVD on these substrates is a breakthrough innovation for functional material development. However, several challenges remain, e.g. understanding film growth mechanisms on foams, their impact on electrochemical processes, and optimizing the performance of coated foams across various applications through an understanding of the electrochemical phenomena occurring inside and on the surface of the coated foams. This review provides the first thorough overview of the current state-of-the-art in this area and suggests innovative solutions to the challenges encountered. It reports the various properties of films on foams reported in literature, compares the electrochemical performance of PVD-coated foams for Oxygen Evolution Reaction (OER)/Hydrogen Evolution Reaction (HER) catalysis, and energy storage applications, and discusses the mechanisms that explain their performance. Additionally, the review offers an analysis of existing research and introduces a novel numerical methodology, integrating Direct Simulation Monte Carlo (DSMC), Particle-in-Cell Monte Carlo (PICMC), and kinetic Monte Carlo (kMC) techniques to facilitate the characterization of coatings within the foams.

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Single crystalline Cu7Te4 nanorods were obtained from a two-step synthesis route. The first step is the electrochemical deposition of self-standing tellurium nanorods on Pt-coated glass electrode in an ionic liquid electrolyte acting as a structuring solvent. Afterwards, soft chemical transformation in Cu7Te4 is performed by immersing the Te-covered electrode in a Cu(II) solution in presence of ascorbic acid acting as reducer at room temperature and atmospheric pressure. Tellurium seems to undergo a reaction of disproportionation induced by the simultaneous presence of Cu(II) and Cu(I) into Te(IV) and Cu7Te4, which is supported by thermodynamic considerations. The copper telluride nanorods were analyzed by XRD, SEM-EDX, HRTEM-FFT/SAED, EELS and XPS that allowed to set the required parameters in terms of molar ratio of precursors in the bath to induce the targeted chemical reaction. The analyses highlight the obtention of single crystalline Cu7Te4 with a homogeneous chemical composition along the nanorods. A detailed analysis of the microstructure shows the presence of stacking local defects, leading to curved nanostructures.

The anticorrosive performance of pulse electrodeposited Zn–Mn deposits was investigated according to the salt spray test DIN EN ISO 9227, commonly used in the automotive industry. A comprehensive analysis of the corrosion products was conducted on the surface and cross‐sections via X‐ray diffraction and scanning electron microscopy to define the corrosion mechanisms involved. The results revealed a significant enhancement of the anticorrosive performance of Zn–Mn deposits over commercial Zn through a complex corrosion mechanism. The protective coating evolves continuously with exposition time. A preferential dissolution of Mn is observed leading to the formation of a compact layer of zinc hydroxychloride. Moreover, an overlayer of manganese oxide and zinc oxide is highlighted at prolonged exposures due to an increase in interface pH.

SnSe is semiconductor with various applications in optoelectronic devices, but its synthesis still facing chal-lenges. Here, an original approach to tune the morphology, the optical properties and microstructure of SnSe films is proposed, based on the change of pulse duration during electrodeposition. The syntheses were carried out at a unique applied potential of-0.55 V vs AgCl/Ag with pulse durations (tON) ranging from 50 ms to 500 ms. The microstructure was systematically studied with SEM, TEM, XRD and XPS characterizations. First, the for-mation of SnSe of compact films without pinholes is demonstrated, with no significant change of composition (Se/Sn ratio close to 1:1). All the films are crystalized according to the Pnma orthorhombic phase with a pref-erential growth direction perpendicular to the (111) direction. The increase of pulse duration from 50 to 500 ms reduces the crystallinity of film, but less Se and SnO2 by-products are formed. Finally, the absorption coefficient of the films was extracted from ellipsometric measurements and evaluated in the near-edge region to evaluate the optical bandgaps. The results confirmed a slight change in the optical bandgap, from 1 to 1.1 eV. This work opens new alternative to tune physico-chemical properties of SnSe films.

Pure monoclinic single crystalline Ag2Te nanorods were synthesized by a two-step method. The first step concerns the electrodeposition of self-standing Te nanorods in an ionic liquid medium, taking advantage of its templating properties. These obtained nanorods are single crystalline with growth direction along the [001] axis in the hexagonal lattice. The average diameter of the as-deposited Te nanorods is 60 +/- 13 nm with less than 300 nm long. Afterwards, the resulting nanostructured Te film is immerged in a dedicated silver-based bath in order to be transformed into Ag2Te binary compounds by a combined mechanism of chemical cementation and topotactic transformation. The chemical analysis reveals that the final nanostructures exhibit a slight excess of silver and TEM-SAED analysis shows that they are still single crystalline with an increase of the initial diameter, less than 30%. HR-TEM highlights the presence of an intermediate stutzite phase and the hessite phase alpha-Ag2Te is obtained at the end of the synthesis process.

In this study, we describe a reproducible process route to form highly mesoporous, mechanically robust and handleable aerogels based on entangled PEDOT:PSS nanofibers. The conservation of the alcogel 3D network is ensured via thorough control of the solvent exchange and drying steps. Particular consideration has been given to metrology, allowing us to fully characterize the thermoelectric properties of the aerogels. The interconnected fibrillar morphology provides good electrical conductivity and mechanical properties by forming effective pathways for both electron transfer and sustaining mechanical forces. The Seebeck coefficient does not seem to be impacted by the high porosity of the material. Finally, the positive impact of mesoporosity on thermal transport and in particular on the lattice part of the thermal conductivity (klat) is demonstrated here for the first time. Thus, this pure PEDOT:PSS aerogel exhibits very interesting structural and charge transport properties. The high power output of 2 µW, measured for a temperature gradient of 36.5 K on a single aerogel sample, highlights the possibility of integrating PEDOT:PSS aerogels into thermoelectric generators. Graphical Abstract

Measuring the thermoelectric transport properties of a material is a prerequisite to determining its usefulness for application in waste heat recovery or cooling and the basis for devising improvement strategies. While well-established characterization methods exist for bulk samples, characterization of microscale samples remains challenging. This usually results in incomplete characterization such as restriction to study of the thermal transport properties, which can be misleading. While elaborate microdevices for complete thermoelectric characterization have been fabricated, a demanding transfer of the samples onto these devices is generally required and establishing sufficient electrical contact can be challenging in this case. Therefore a complete and transfer free in-plane characterization method for samples obtained by deposition processes was developed. The approach is based on expanding a well-established self-heating technique for the measurement of electrical and thermal conductivity to allow, in addition, for the measurement of the Seebeck coefficient. The fabrication exclusively involves photolithography and wet etching, with no need for other steps like electron-beam lithography and a lift-off process. The accuracy of the method is verified by numerical studies closely mimicking the actual measurement process, comparison to measurements on simultaneously deposited reference samples and results from literature.

Zinc oxide (ZnO) thin films were prepared on glass substrates with three different lithium salt precursors (acetate, chloride and nitrates) with Li/Zn atomic ratio varying between 0% and 20% using sol-gel deposition and spin-coating technique. The aim of the work was to compare the physical properties of lithium containing ZnO thin layers obtained using different Li salt precursors; in order to identify the most suitable one. The X-ray diffraction measurements showed that all 500 degrees C annealed films were polycrystalline. The samples prepared from lithium nitrates solutions showed a preferred orientation along c-axis (002) and their crystallites sizes are much larger compared to other Li source. The ultraviolet-visible transmission spectra confirmed the good transparency of all ZnO films with an average transmission around 85 % in the visible range. The optical band gap values varied between 3.19 eV and 3.28 eV. All the results revealed that the ZnO-Li films prepared with LiNO3 exhibit the highest crystallographic quality and the best optical and electrical properties compared to C2H3LiO2 and LiCl containing precursors.

The forged Inconel 718 anodic dissolution at fixed applied current density was investigated in different nitrate sodium based electrolytes, namely in NaNO3 8 wt% and 20 wt%, in NaNO3 15 wt% + NaClO3 20 wt%, and in NaNO3 20 wt% + sulfosalicylic acid 2 wt%. The analysis of the different anodic products on the surface sample, by X-Ray diffraction, Scanning Electron Microscopy, and Energy Dispersive X-ray spectroscopy, revealed a presence of oxides mainly constituted of Nb and Ti oxides and a smaller amount of γ″ phase precipitate than in raw material. Inductively coupled plasma (ICP) analysis has shown that the main elements of the matrix (Fe, Cr, Ni) are soluble in all tested electrolytes while Nb content is below the detection threshold in pure NaNO3 electrolyte and in 15 wt% NaNO3 + 20 wt% NaClO3. However, in presence of sulfosalicylic acid, acting as chelating agent, the amount of anodic products on the surface sample has considerably reduced comparatively to other tested electrolytes and Nb was detected by ICP analysis as additional element in the electrolyte. Therefore, this work shows that the Inconel 718 super alloy can be homogenously anodized by the use of an adapted chelating electrolyte, opening up possibilities for efficient electrochemical machining processes.

The sodiation-desodiation process of sputtered amorphous electrochromic tungsten oxide coatings in an aqueous-based medium was simultaneously monitored over 99 cycles by cyclic voltammetry and in situ spectroscopic ellipsometry. This allowed extracting the evolution of optical and geometrical parameters upon cycling. The resulting electrochemical coloring-bleaching process was dynamically fitted in the 1.8-2.8 eV optical range with a four-phase model including a constrained spline parametrization of the dielectric function. This allows real time access to thickness, surface roughness, and dielectric function of ${{\rm Na}_x}\!{{\rm WO}_3}$NaxWO3. The temporal evolution of the latter in the fully colored state was used to highlight the porosity extent of the probed coating of opened morphology. The designed spectroelectrochemical approach was applied to map the temporal evolution of the $\rm Na$Na content (${x}$x in ${{\rm Na}_x}\!{{\rm WO}_3}$NaxWO3) during and between cycles, taking into account the intricate interplay between charge density, thickness, and electrolyte uptake.

The reversible intercalation of sodium ion into tungsten oxide WO3 appears as an interesting alternative to hydrogen or lithium ion reduction in order to get the characteristic transition from clear transparent to bluish coloration in electrochromic devices, but it has been comparatively less considered. In order to address further viable all-ceramic devices based on sodium ion intercalation and overcome the issue of WO3 degradation in aqueous media, three configurations of WO3 thin film-based electrochromic half-cells were tested, namely in (i) aqueous acidified Na2SO4 electrolyte, (ii) room temperature ionic liquid BEPipTFSI electrolyte and (iii) aqueous acidified Na2SO4 electrolyte associated with an amorphous NASICON-cap onto WO3 film. We compared their electro-optical characteristics during 100 voltammetry cycles, including the Na+ diffusion coefficient calculated through electrochemical method. It is found that sputter-deposited amorphous WO3 thin films on transparent conductive substrates is promising for electrochromic all-ceramic devices based on Na ion insertion. Electrochemical characterization in aqueous medium is not relevant to extract relevant data when WO3 is in direct contact with the electrolyte as the electrochromic film is progressively dissolved. In contrast, WO3 capped with oxide amorphous Naion conductor readily operates over 100 cycles, the capping layer preventing degradation by the aqueous medium. Alternatively, ionic liquid does not degrade the WO3 film and can be employed to efficiently characterize the electro-optical performances. (C) 2020 Elsevier Ltd. All rights reserved.

Ba 0.85 Ca 0.15 Zr 0.10 Ti 0.90 O 3 (BCZT) lead-free ceramics demonstrated excellent dielectric, ferroelectric, and piezoelectric properties at the morphotropic phase boundary (MPB). So far, to study the effect of morphological changes on dielectric and ferroelectric properties in lead-free BCZT ceramics, researchers have mostly focused on the influence of spherical grain shape change. In this study, BCZT ceramics with rod-like grains and aspect ratio of about 10 were synthesized by surfactant-assisted solvothermal route. X-ray diffraction (XRD) and selected area electron diffraction (SAED) performed at room temperature confirm the crystallization of pure perovskite with tetragonal symmetry. Scanning electron microscopy (SEM) image showed that BCZT ceramics have kept the 1D rod-like grains with an average aspect ratio of about 4. Rod-like BCZT ceramics exhibit enhanced dielectric ferroelectric (ɛ r = 11,906, tanδ = 0.014, P r = 6.01 μgC/cm 2 , and E c = 2.46 kV/cm), and electrocaloric properties (Δ T = 0.492 K and gZ = 0.289 (K·mm)/kV at 17 kV/cm) with respect to spherical BCZT ceramics. Therefore, rod-like BCZT lead-free ceramics have good potential to be used in solid-state refrigeration technology.

In this work, we report a study of the electrodeposition of SnSe. Considering the difficulty to stabilize the baths containing Sn(II) and Se(IV) precursors, we investigated the benefits of using sodium oxalate as a complexing agent. Preliminary cyclic voltammetric (CVs) experiments were performed to study the electrochemical behavior of tin and selenium redox systems within this specific electrolyte solution. The study revealed that the oxalate reagent stabilizes the bath chelating Sn(II) and then preventing the precipitation of SnO2. From the CVs, a growth mechanism is proposed and a synthesis potential window is defined, in which the electrodeposition of SnSe films was investigated. Between −0.5 and −0.6 V vs sat. AgCl/Ag, the deposits exhibit typical polycrystalline SnSe needle-like grains. SnSe was shown by Raman spectroscopy and the XRD patterns display an orthorhombic single-phase for this compound. Additional Mössbauer analyses confirm the presence of Sn(II), which is in good agreement with the chemical composition of SnSe films. Moreover, a cross-analysis between the methods shows also the presence of SnSe2 in minor proportion. The depth profile analyses of the samples reveal an in-depth homogeneity as well as the presence of oxygen at the layer surface.

This work shows the interest to use a real time, white laser-based ellipsometer to characterize a complex electrolyte|electrode interface during an electrochemical process in an aqueous-based medium. This method is proposed to probe electrochemical interfaces that are usually not suitable to the full extent application of ellipsometry due to great disturbance of the reflected light flux provoked by gas evolution or roughness. In situ spectroelectrochemical ellipsometry combining such a visible super continuum fiber laser-band source was not previously reported to the best of the authors’ knowledge. The setup was employed to monitor an electrochemical process whose mechanism was previously incompletely described: the prespark anodization regime of the plasma electrolytic oxidation process of the Mg alloy AZ91D in the 3M KOH electrolyte. Above the anodization voltage of 4 V, the side water oxidation reaction induced light diffusion that reduces reflected light beam intensity. The process is monitored in an extended voltage range from 4 to 40 V and in an extended spectral range (495–800 nm). In the presented case, the use of a visible super continuum fiber laser-band source enhanced the signal-to-noise ratio giving access to a deeper picture of the triplex layer structure during surface repassivation by monitoring the evolution of the outer, inner, and interfacial layers.

Tabulated real (n) and imaginary (k) parts of the complex refraction index of Na0.2WO3 vs energy (eV) and wavelength (nm)