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In the present study, an ethylene glycol-based electrolyte is used to electrodeposit copper onto zinc for the synthesis of the Zn/Cu/Sn stack, precursor of Cu2ZnSnS4. The employed solution contains diethanolamine (DEA) which supports the formation of amine-complexes, whose features are studied by UV–vis absorption, ESI-MS, and FTIR measurements, providing insight on the optimal concentration of DEA for copper complexation. Cyclic voltammetries (CVs) are carried out at increasing [DEA]/[Cu2+] ratios, highlighting the amine effect on the reduction potential of the copper species. The displacement reaction between copper and zinc is investigated by immersion potential measurements, showing a direct correlation to the voltammetric data. The optimized copper solution resulted in a negligible displacement contribution, allowing the electrochemical synthesis of Mo(sub)/Zn/Cu/Sn stack on a relatively large area (4 cm2). The metallic precursor is analyzed by SEM/EDS, AFM, XRD, and GDOES techniques. Finally, the kesterite CZTS phase is obtained through reactive annealing with elemental sulfur and it is characterized by SEM/EDS, XRD, and Raman spectroscopy. Photoelectrochemical water splitting on CZTS/CdS/Pt heterostructure is carried out in an aqueous solution at pH 6.85, showing a photocurrent of -5.05 mA/cm2 at 0 V vs RHE. A maximum applied bias photon-to-current efficiency (ABPE) value of 2.15% was found at 0.84 V bias.

Earth-abundant and non-toxic Kesterite-based Cu2ZnSnS4 (CZTS) thin film solar cells are successfully fabricated on flexible Molybdenum (Mo) foil substrates by an electrodeposition-annealing route. A well-adherent, densely packed, homogeneous, compact, and mirror-like CZT precursor is initially produced through electrodeposition by using a rotating working electrode. Subsequently, the co-electrodeposited CuZnSn (CZT) precursor is sulfurized in quartz tube furnace at 550 °C for 2 h in N2 atmosphere with the presence of elemental sulfur in order to form CZTS. Different characterization techniques like XRD, SEM, HR-TEM, Raman, and Photoluminescence demonstrate that almost phase-pure CZTS formed after sulfurization. A flexible Al/Al-ZnO/i-ZnO/CdS/CZTS/Mo foil solar cell is produced, where CdS is deposited by chemical bath deposition and transparent conducting oxide (TCO) is deposited by DC sputtering. The CZTS solar device shows a 0.55% power conversion efficiency on flexible Mo foil substrate and it constitutes the first prototype of this kind of solar cell produced by electrodeposition-annealing route without any surface modification of the Mo substrate. Graphic abstract: [Figure not available: see fulltext.].

In this work, Cu-Zn-Sn (CZT) is co-electrodeposited onto a flexible Mo substrate exploiting an alkaline bath (pH 10). The plating solution is studied by cyclic voltammetry, highlighting the effects of potassium pyrophosphate (K4P2O7) and EDTA-Na2 on the electrochemical behavior and stability of the metallic ionic species. The optimized synthesis results in a homogeneous precursor layer, with composition Cu 44 ± 2 at. %, Zn 28 ± 1 at. %, and Sn 28 ± 2 at. %. Soft and reactive annealing are employed respectively to promote intermetallic phase formation and sulfurization of the precursor to obtain CZTS. Microstructural (XRD, Raman), morphological (SEM), and compositional (EDX, XRF) characterization is carried out on CZT and CZTS films, showing a minor presence of secondary phases. Finally, photo-assisted water splitting tests are performed considering a CZTS/CdS/Pt photoelectrode, showing a photocurrent density of 1.01 mA cm−2 at 0 V vs. RHE under 1 sun illumination. Graphical abstract: [Figure not available: see fulltext.]

In this work, the production of low cost and environment friendly anodes for sodium ion batteries is investigated. Algae are selected as bio-source of non-graphitic Hard Carbon (HC) with open structure acting as intercalation active material for Na ions storage. Chlorella vulgaris algae were pyrolyzed at temperatures comprised between 800 and 1100 °C. The decomposition products have been characterized with Scanning Electrode Microscope (SEM) and X-Ray Diffraction (XRD) analyses and their structure compared to one of the synthetic commercial HC. Thermogravimetric analysis (TGA) allowed to assess the decomposition process throughout the selected temperature scan. The obtained algae-derived HC is tested as anodic material for Na-ion battery, investigating the effect of pyrolysis temperature on the electrochemical behaviour. Their performances are compared with respect to a commercial synthetic HC active material. The results allow to consider algae as an environmentally benign and sustainable high added-value material for the production of HC anodes for Na-ion batteries. Graphic abstract: [Figure not available: see fulltext.]

Electrospinning is a powerful and versatile technique to produce efficient, specifically tailored and high-added value anodes for lithium ion batteries. Indeed, electrospun carbon nanofibers (CNFs) provide faster intercalation kinetics, shorter diffusion paths for ions/electrons transport and a larger number of lithium insertion sites with respect to commonly employed powder materials. With a view to further enhance battery performances, red phosphorous (RP) is considered one of the most promising materials that can be used in association with CNFs. RP/CNFs smart combinations can be exploited to overcome RP low conductivity and large volume expansion during cycling. In this context, we suggest a simple and cost effective double-step procedure to obtain high-capacity CNFs anodes and to enhance their electrochemical performances with the insertion of red phosphorous in the matrix. We propose a simple dropcasting method to confine micro- and nanosized RP particles within electrospun CNFs, thus obtaining a highly efficient, self-standing, binder-free anode. Phosphorous decorated carbon mats are characterized morphologically and tested in lithium ion batteries. Results obtained demonstrate that the reversible specific capacity and the rate capability of the obtained composite anodes is significantly improved with respect to the electrospun carbon mat alone.