This work presents a synthesis approach for forming a Cu2O/ZnO composite with sphere- and sheet-like morphologies for application in the photocatalytic degradation of imidacloprid, a pesticide and emerging contaminant frequently detected in rivers, aquifers, lakes, and wastewater treatment plants near agricultural areas. The composite was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), while its morphology was analyzed by FESEM and TEM. Optoelectronic studies revealed that the Cu2O/ZnO composite absorbs both visible and ultraviolet radiation, covering approximately 45-48% of the solar spectrum, positioning it as a promising alternative to UV-dependent photocatalysts such as TiO2. When applied in aqueous media under simulated solar irradiation, the Cu2O/ZnO composite achieved 43% imidacloprid degradation after 3 h, a moderate performance attributed to charge carrier accumulation and recombination at the composite interface. The introduction of hydrogen peroxide effectively suppressed recombination, leading to 97% imidacloprid removal within the same reaction time and significantly enhanced mineralization efficiency. Mechanistic analysis indicated that hydroxyl radicals (center dot OH) are the dominant reactive species responsible for pesticide degradation, while superoxide radicals play a negligible role. These results demonstrate the strong potential of the Cu2O/ZnO/H2O2 system for efficient solar-driven pesticide removal in water treatment applications.

Developing efficient, stable, and cost-effective electrocatalysts for the oxygen reduction reaction in acidic media remains a critical challenge for advancing technologies like proton exchange membrane fuel cells . This work explores the use of transition metal oxides integrated into a carbon paste matrix as PGM-free alternatives. We synthesized α-Fe2O3, Co3O4, and CoFe2O4 nanoparticles and incorporated them into a composite electrode consisting of multi-walled carbon nanotubes and a N-octylpyridinium hexafluorophosphate ionic liquid binder. Preliminary electrochemical screening by cyclic voltammetry in O2-saturated 0.1 M HClO4 suggested a qualitative activity trend: MWCNTs/IL/ α-Fe2O3 > MWCNTs/IL/CoFe2O4 > MWCNTs/IL/Co3O4 > MWCNTs/IL. The optimized MWCNTs/IL/α-Fe2O3 composite exhibited enhanced ORR performance, with an onset potential of approximately +350 mV vs. RHE and a current density of 11 mA cm-2. Such activity was attributed to a synergistic effect between the well-dispersed α-Fe2O3 nanoparticles and the conductive MWCNTs/IL matrix. Electrochemical impedance spectroscopy (EIS) confirmed this synergy, showing that the α-Fe2O3 composite had a charge-transfer resistance of 1046 Ω, indicating the fastest reaction kinetics among the oxide composites. Furthermore, rotating ring-disk electrode studies demonstrated the catalyst's selectivity, favoring the direct 4-electron pathway to water with minimal hydrogen peroxide production . The α-Fe2O3 system also exhibited operational stability in acid media.

Diclofenac (DCF) is a prevalent aquatic contaminant poorly removed by conventional wastewater treatment plants. This study investigates the photocatalytic degradation of DCF under simulated sunlight using nanoparticulate kesterite semiconductors Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe), focusing on efficiency, stability, degradation pathways, and environmental implications. CZTSe exhibited superior photocatalytic performance, achieving 83% DCF removal within 60 min with a pseudo-first-order rate constant of 3.0 × 10- 2 min- 1, whereas CZTS reached 68% removal with 1.7 × 10- 2 min- 1. Both photocatalysts maintained stable activity after four reuse cycles. Total organic carbon analysis confirmed progressive DCF mineralization, i.e., the conversion of organic carbon into CO2 and inorganic species. HPLC-MS analysis identified six transformation products generated by DCF degradation, corresponding to the conversion of the parent molecule into intermediate compounds. In silico ecotoxicity assessment using predictive computational models indicated reduced bioaccumulation potential of DCF after treatment; however, some transformation products exhibited higher environmental persistence and retained or increased predicted toxicity. Reactive species experiments demonstrated that superoxide radicals (•O2⁻) were the main reactive species, followed by hydroxyl radicals (•OH). These findings demonstrate that CZTS and, particularly, CZTSe are efficient and reusable visible-light photocatalysts for DCF removal while providing new insights into degradation pathways, mineralization, reactive oxygen species, and transformation-product ecotoxicity, underscoring the importance of assessing degradation by-products in advanced oxidation processes.

Ammonia (NH3) is an essential energy vector because it is an important source of hydrogen. Therefore, the generation of NH3 by means of green processes with renewable energies and without carbon dioxide emissions is relevant. In this work, the electrochemical nitrogen reduction reaction (NRR) to obtain ammonia is studied. The working electrode was a Fe-Mo mixture with its oxides on the surface. By means of characterization techniques such as FESEM, XPS, Raman Spectroscopy, and XRD, it was determined that the electroactive surface was a mixture of oxides, mainly hematite (alpha-Fe2O3) and molybdenum dioxide (MoO2). This electrode shows a geometric yield rate of 4.73 mu g h-1 cm-2 with a faradaic efficiency (FE%) of 8.22% in 0.1 mol L-1 PBS. Using the SHINERS methodology supported by DFT calculations, hydrazine was identified as a reaction intermediate, indicating an alternative associative mechanism.

This work explored the electrochemical and photovoltaic performance of a dye-sensitized solar cell sensitized and co-sensitized with the organic dyes RK1 and MK-2. By combining both dyes in optimal proportions (RK1/ MK-2 = 0.3 mM/0.2 mM), a notable synergistic effect was observed, resulting in a red shift in the absorption spectrum and an effective reduction in the bandgap. These changes not only optimized light harvesting but also led to clear improvements in device efficiency. Electrochemical analysis revealed key differences in the electron transfer mechanisms between the pure dyes, highlighting the benzothiadiazole group that can suppress undesirable recombination. Under standard illumination conditions (AM 1.5G), the co-sensitized cell achieved a conversion efficiency of 5.86%, significantly outperforming the yields obtained with each dye separately. An improvement in EQE was observed around 321 nm, attributed to the efficient conversion of high-energy UV photons into visible photons, reducing thermal losses and enhancing overall photon utilization. In addition, this configuration showed particularly favorable behavior in terms of recombination dynamics: the electron transfer resistance (R) reached 29.88 Omega, with values far above those recorded for cells with MK-2 (R = 7.86 Omega) or RK1 (R = 7.57 Omega). Taken together, these results suggest that the combination of RK1 and MK-2 functions as a complementary system, where one extends spectral absorption and the other acts as a barrier against recombination, thereby enhancing the overall device efficiency.

The combination of ZnO nanotubes and SnS nanoparticles in core-shell nanoarchitectures has potential advantages for photoelectrochemical applications due to increased absorption, optimized band alignment, improved stability and large surface to volume ratios. The fabrication of these structures usually involves a three-step process, limiting their application when high throughput is required. This work presents a synthesis method based on SILAR deposition, a low cost technique, that successfully deposits the nanoparticles while simultaneously forming nanotubes, reducing the number of synthesis steps to two. In order to evaluate the resulting nanostructures for photoelectrochemical applications, morphological and optical characterizations of the resulting nanorod and nanotube arrays are performed. The absorption spectra of each sample is reconstructed through the Tauc plot method, with the samples showing both a direct and an indirect bandgap of SnS. It is shown that the formation of nanotubes affects the strain in the SnS shell, modifying the Urbach tail by generating mid-gaps states, which has potential as a control parameter to tailor optical performance. Lastly, the polarization properties of the 1D nanostructures associated with their elongated morphology are explored, which showed a clear relationship between underlying nanorod and nanotube morphology, the scattering properties and the polarization state of light.

The optical properties of CsPbBr3 are studied with temperature dependent spectroscopic techniques. The samples are obtained from a method that has 10 % Pb waste compared with conventional ones. The dependence with temperature between 30 K and room temperature of the optical transmittance and photoluminescence is measured. Near bandgap optical properties are governed by structures originated in free excitons. Using the Elliott model for excitonic absorption, the dependence with temperature of bandgap energy and exciton binding energy are obtained. Both increase with temperature increase. Also, the width of the excitonic absorption and the inter-band absorption, which is assimilated to Urbach energy, were studied. Several models are used to extract parameters from these data. The excitonic absorption width follows the Segall model giving an exciton optical phonon interaction as the dominant term at room temperature. From several fittings, an effective optical phonon energy between 23 and 32 meV is obtained. The Urbach energy at 30 K reaches 10 meV which is related to a good crystalline quality of the samples. Several experimental results show that the origin of the photoluminescence is produced by direct recombination of free excitons. The first one is the similarity of the temperature dependence of photoluminescence width with the one of excitonic absorption. The second one is based in the activation energies obtained from the dependence of the integrated photoluminescence with temperature, one of which coincides with Excitonic Biding Energy. The third one is related to the dependence of the Stokes Shift with temperature which corresponds to the Gurioli model of excitonic thermalization. The last one comes from the dependence of the time resolved photoluminescence. Using rate equations, a radiative and non-radiative monomolecular time constant between 32 and 50 ns and an exciton-exciton annihilation rate constant between 1.0 and 6.0 x 10 7 cm(3)/s are obtained.

Cu2ZnSnSe4 (CZTSe) nanoparticles (NPs) were successfully synthesized via a solvothermal method. Their structural, compositional, morphological, optoelectronic, and electrochemical properties have been characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Field-emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), UV–vis absorption spectroscopy, and electrochemical impedance spectroscopy (EIS) techniques. Porosimetry and specific surface area in terms of the Brunauer–Emmett–Teller (BET) technique have also been studied. XRD indicates the formation of a polycrystalline kesterite CZTSe phase. Raman peaks at 173 and 190 cm−1 confirm the formation of a pure phase. TEM micrographs revealed the presence of nanoparticles with average sizes of ~90 nm. A BET surface area of 7 m2/g was determined. The CZTSe NPs showed a bandgap of 1.0 eV and a p-type semiconducting behavior. As a proof of concept, for the first time, the CZTSe NPs have been used as a visible-light-driven photocatalyst to Congo red (CR) azo dye degradation. The nanophotocatalyst material under simulated sunlight results in almost complete degradation (96%) of CR dye after 70 min, following a pseudo-second-order kinetic model (rate constant of 0.334 min−1). The prepared CZTSe was reusable and can be repeatedly used to remove CR dye from aqueous solutions.

Transition metal oxides are a great alternative to less expensive hydrogen evolution reaction (HER) catalysts. However, the lack of conductivity of these materials requires a conductor material to support them and improve the activity toward HER. On the other hand, carbon paste electrodes result in a versatile and cheap electrode with good activity and conductivity in electrocatalytic hydrogen production, especially when the carbonaceous material is agglomerated with ionic liquids. In the present work, an electrode composed of multi-walled carbon nanotubes (MWCNTs) and cobalt ferrite oxide (CoFe2O4) was prepared. These compounds were included on an electrode agglomerated with the ionic liquid N-octylpyridinium hexafluorophosphate (IL) to obtain the modified CoFe2O4/MWCNTs/IL nanocomposite electrode. To evaluate the behavior of each metal of the bimetallic oxide, this compound was compared to the behavior of MWCNTs/IL where a single monometallic iron or cobalt oxides were included (i.e., α-Fe2O3/MWCNTs/IL and Co3O4/MWCNTs/IL). The synthesis of the oxides has been characterized by X-ray diffraction (XRD), RAMAN spectroscopy, and field emission scanning electronic microscopy (FE-SEM), corroborating the nanometric character and the structure of the compounds. The CoFe2O4/MWCNTs/IL nanocomposite system presents excellent electrocatalytic activity toward HER with an onset potential of −270 mV vs. RHE, evidencing an increase in activity compared to monometallic oxides and exhibiting onset potentials of −530 mV and −540 mV for α-Fe2O3/MWCNTs/IL and Co3O4/MWCNTs/IL, respectively. Finally, the system studied presents excellent stability during the 5 h of electrolysis, producing 132 μmol cm−2 h−1 of hydrogen gas.

Samples of ZnO were prepared by sol-gel and deposited by dip-coating. The influence of synthesis conditions on the optical properties were studied in different sets of ZnO films, synthesized by alternately varying the following parameters: addition of additives to the precursor solution, Al doping percentage and number of layers. The optical properties of the obtained films were studied by transmittance, being typically >90 % at 600 nm. The absorption edge for undoped samples showed a structure due to exciton formation at room temperature. The bandgap energy E- g , was between (3.227 +/- 0.010) eV and (3.275 +/- 0.010) eV for undoped samples, increasing to (3.352 +/- 0.010) eV for Al doped ones (10 % Al/Zn in solution with additives). For intermediate 5 % doping the mean bandgap energy was (3.315 +/- 0.015) eV. A similar value (3.320 eV +/- 0.010) eV was obtained for 10 % Al/ Zn when no additives were included. Doped samples showed a smoother absorption edge. This edge shape evolution was studied by Urbach band tail analysis. The Urbach band tail parameter E-U increased with doping, varying from 30 meV to 90 meV and increasing as E g increases. This correlation describes the influence of impurity states in the structure and optical properties of the material.

Fluorine-doped tin oxide (FTO) is among the most used transparent conductive oxides (TCOs) in phototovoltaic devices such as photoelectrochemical and solar cells. Preparation of films on these TCOs can be achieved by several deposition techniques including electrodeposition. Among the several cleaning and activation procedures before a thin film deposition there is the oxygen plasma treatment, which has been successfully applied on several kind of substrate materials. Surprisingly, the use of this step on TCOs previously to the electrodeposition of a film is not a usual practice. Here we present a detailed study on the consequences of oxygen plasma process over FTO electrodes that are subsequently employed in several electrochemical reactions of practical importance. Open circuit potential (OCP) measurements from oxygen plasma treated FTO have proven the resorption of ions and/or solvent molecules in aqueous electrolyte following a pseudo-second order kinetic. Electrochemical reactions were quite sensible to the oxygen plasma treatment, even under mild conditions. In all cases FTO become deactivated for such electrochemical processes independently of the plasma set up employed except for metal electrodeposition. Partial recovering of the electrochemical response of FTO in the ferri/ferro system after annealing at 450 degrees C explains why oxygen plasma process is worthy only for other deposition techniques such as spray pyrolysis where similar temperatures are employed. Electrochemical Impedance Spectroscopy (EIS) analysis revealed a decrease of the majority carrier density (ND). This is mainly attributed to the oxyanion implantation on oxygen vacancies sites during the plasma process thus explaining the loss of activation of FTO. Energy level diagrams reveal the decrease of degeneracy of FTO towards an n-type semiconducting SnO2 film which is also supported by ultraviolet photoelectron spectroscopy (UPS). A band gap energy dependence with the plasma conditions allowed to check the filling of oxygen vacancies on the FTO surface without discard the loss of fluorine. Anodic polarization in acid media proved the impossibility of oxygen vacancies restitution, being the dominating process the partial etching of FTO.

Electrodeposition of conformal and compact SnO2 films on transparent conductive oxides (TCOs) has been hardly achieved thus limiting its application in fully solid solar cells such as those based in perovskite absorbers. Here are presented high-quality n-type semiconducting tin (VI) oxide (SnO2) thin films, successfully grown using a hybrid potentiodynamic/potentiostatic approach on both ITO and FTO coated glass substrates after a detailed optimization that included both annealing steps between eletrodepositions. A solution chemistry study together with a spectrophotometric analysis was useful to determine the one-hour time window of stability for the chosen electrolyte as source of tin. Formation mechanisms based in thermodynamic data and accumulated mass measurements using an electrochemical quartz crystal microbalance (EQCM) are discussed. From the EQCM study the growth rate of films was also estimated in good agreement with high resolution transmission electron microscopy (HR-TEM) analysis. Field emission scanning electron microscopy (FE-SEM) images and X-ray diffraction (XRD) data revealed that substrates are well-covered, crystalline, conformal and free of defects (e.g. without pinholes). The absence of these defects was also well supported by cyclic voltammetry measurements using the ferricyanide/ferrocyanide redox couple. XPS also confirmed the presence of Sn4+ in optimized films. From the optical properties, after carefully eliminating the influence of oscillations due to interference, a direct bandgap energy at 3.60 eV can be deduced. Another indirect bandgap energy at 3.30 eV can also be possible. The hybrid potentiodynamic/potentiostatic protocol to prepare SnO2 paves a way to prepare compact, transparent and well covering films suitable as electron transporting layer (ETL) for applications in both photoelectrochemical and solid-state solar cells.

The cleaning and/or activation of electrodes for electrochemical purposes using the oxygen plasma treatment has been widely used because of its proven effectiveness to improve the properties of electrodes. Beyond its cleaning effect, the plasma can either create stepped and functionalized carbon-based materials which are active for specific electroanalytes and increase their capacitance [1]. Prussian Blue can also be activated by creating oxygen rich sites thus enhancing its electrochromism [2]. In the case of transparent conductive oxides (TCOs) electrodes such as FTO and ITO-coated glass this treatment has proven to be suitable in the preparation of spray-pyrolyzed titania thin films used as blocking hole layer or electron transporting layer in efficient third generation solar cells [3]. However, the role of this treatment on TCOs when used for electrochemical purposes has not been deeply explored yet. The reason to carry out this study lies in the great number of electrochemical processes that are usually employed for the growth of wide and middle band gap semiconductor metal oxides and chalcogenides with applications in photoelectrochemical and photovoltaic cells [4]. To assess the role of the oxygen plasma, FTO was chosen as TCO reference material and the effect of different time exposure and power of plasma was analysed by electrochemical polarization in aqueous media for both anodic and cathodic directions. In the former, PbO2 electrodeposition and oxygen evolution reaction (OER) were considered. In the later, hydroxide generating reactions that usually precipitate in presence of transition metal cations were studied: i) the oxygen reduction reaction (ORR, Figure 1), ii) hydrogen peroxide reduction. Further, the reduction of S8 in DMSO media to sulphide ion was also considered as an aprotic media to growth chalcogenides. Interestingly, all these electrochemical reactions exhibited an increased activation overpotential. The behaviour of treated FTO for OER demonstrated the as implanted oxyanions do not act as source of molecular oxygen as previously claimed [5]. This was verified by the poorly response of ORR after anodic polarizations in acid media. Besides, contact angle measurements allowed to estimate the energetic of the FTO surfaces being these energies correlated with open circuit potential values. Capacitance (Mott-Schottky plots), XPS, UPS and UV-Vis spectroscopy were used to study the semiconductor energy levels of both treated and untreated FTO electrodes. The oxyanion implantation in the oxygen vacancies would be responsible of the sharply diminution of the ORR wave. However, the electrochemical response of the well-known Ferri/Ferro couple only suffered changes under highly aggressive treatments, i.e. for long times or power. Meanwhile, XRD data has shown only slight changes in the structural features of FTO. We can conclude that oxygen plasma treatment is not suitable in FTO for electrochemical purposes, contrary to other deposition methods. Surprisingly, an exception in metals deposition (Ni and Zn) was found. References [1] S.C. Wang, K.S. Chang, C.J. Yuan, Enhancement of electrochemical properties of screen-printed carbon electrodes by oxygen plasma treatment, Electrochimica Acta 54 (2009) 4937–4943. [2] A-Y. Kim, J. H. Park, D. Byun, J. Kee Lee, Effect of oxygen plasma treatment on the electrochemical properties of Prussian blue electrodes for transparent electrochromic devices, Thin Solid Films 546 (2013) 58-62. [3] J. Baker, K. Hooper, S. Meroni, A. Pockett, J. McGettrick, Z. Wei, R. Escalante, G. Oskam, M. J. Carnie and T. M. Watson, J. Mater. Chem. A 5 (2017) 18643-18650. [4] A. A. Ojo, I. M. Dharmadasa, Electroplating of Semiconductor Materials for Applications in Large Area Electronics: A Review, Coatings 8 (2018) 262. [5] A. Korjenic and K. S. Raja, Electrochemical Stability of Fluorine Doped Tin Oxide (FTO) Coating at Different pH Conditions, Journal of The Electrochemical Society, 166 (2019) C169-C184. Figure 1

A hydrothermal method was successfully employed to synthesize kesterite Cu2ZnSnS4 (CZTS) nanoparticles. X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and optical ultraviolet-visible (UV-vis) spectroscopy were used for characterization of structural, chemical, morphological, and optical properties. XRD results confirmed that a nanocrystalline CZTS phase corresponding to the kesterite structure was formed. Raman analysis confirmed the existence of single pure phase CZTS. XPS results revealed the oxidation states as Cu+, Zn2+, Sn4+, and S2−. FESEM and TEM micrograph images revealed the presence of nanoparticles with average sizes between 7 nm to 60 nm. The synthesized CZTS nanoparticles bandgap was found to be 1.5 eV which is optimal for solar photocatalytic degradation applications. The properties as a semiconductor material were evaluated through the Mott–Schottky analysis. The photocatalytic activity of CZTS has been investigated through photodegradation of Congo red azo dye solution under solar simulation light irradiation, proving to be an excellent photo-catalyst for CR where 90.2% degradation could be achieved in just 60 min. Furthermore, the prepared CZTS was reusable and can be repeatedly used to remove Congo red dye from aqueous solutions.

Oxygen functional groups (OFGs) in graphene oxide (GO) are responsible for its different properties and peculiar reactivity in water and different solvents. A detailed assignment, both theoretical and experimental, of OFGs is still missing, and a full reconstruction of GO electrochemical behavior remains unreached. The spatial localization of OFGs is expected to play an important role in the reduction process, but so far, this important aspect remains undisclosed in the literature. Here, the nature and interactions of adjacent OFGs have been investigated, shedding light on the energetics of their electrochemical reduction. GO chemical modifications upon modulated and controlled electrochemical reduction conditions have been studied, in order to excite and reveal the contribution from single reactive OFGs. The characterization has been conducted via X-ray photoelectron spectroscopic analysis supported by theoretical modelling, to compose a detailed picture of the various local environments participating to the rich chemistry of GO. As a result, the interplay between XPS, cyclic voltammetry and DFT computation allowed for a consistent parallel assessment of both the C 1s ionization energy and the electrochemical reduction potential of the various carbonaceous species of GO.

The development of photoelectrode materials for efficient water splitting using solar energy is a crucial research topic for green hydrogen production. These materials need to be abundant, fabricated on a large scale, and at low cost. In this context, hematite is a promising material that has been widely studied. However, it is a huge challenge to achieve high-efficiency performance as a photoelectrode in water splitting. This paper reports a study of chemical vapor deposition (CVD) growth of hematite nanocrystalline thin films on fluorine-doped tin oxide as a photoanode for photoelectrochemical water splitting, with a particular focus on the effect of the precursor–substrate distance in the CVD system. A full morphological, structural, and optical characterization of hematite nanocrystalline thin films was performed, revealing that no change occurred in the structure of the films as a function of the previously mentioned distance. However, it was found that the thickness of the hematite film, which is a critical parameter in the photoelectrochemical performance, linearly depends on the precursor–substrate distance; however, the electrochemical response exhibits a nonmonotonic behavior. A maximum photocurrent value close to 2.5 mA/cm2 was obtained for a film with a thickness of around 220 nm under solar irradiation.

A CdCO3/CdO/Co3O4 composite has been prepared on nickel foam through a combined hydrothermal-annealing method. An asymmetric hybrid supercapacitor (SC) device was assembled with this composite as the positive electrode and activated carbon was the negative electrode. The SC exhibited a high specific capacitance of 84 F g(-1) @ 1 mA cm(-2), a maximum energy density of 26.3 W h kg(-1), and a power density of 2290 W kg(-1), along with a wide potential window of 1.5 V and long cycle life (92% after 6000 cycles). SCs assembled in series powered various light-emitting diodes and moved an electrical mini-motor.

Graphene oxide (GO) is known to be a 2D metastable nanomaterial that can be reconstructed under thermal annealing into distinct oxidized and graphitic phases. Up to now, such phase transformation, mainly related to epoxide and hydroxyl functional groups, has been usually achieved by thermally treating layers of GO in the solid state. Here, we present the mild annealing of GO dispersed in an aqueous medium, performed at two temperatures, 50 °C and 80 °C, for different intervals of time. We show experimental evidences of the epoxide instability in the presence of water by means of XPS, cyclic voltammetry and Raman spectroscopy, demonstrating the reorganization of epoxide and hydroxyl moieties initiated by water molecules. In fact, at 50 °C an increase in oxygen content is detected in all annealed samples compared to untreated GO, with a transformation of epoxide groups into vicinal diols. On the other hand, at 80 °C the oxygen content decreases towards the initial value since the vicinal diols, previously formed, transform into single hydroxyls and C[double bond, length as m-dash]C bonds. Moreover, the higher temperature annealing likely favours oxygenated functional groups rearrangements and clustering, in accordance with the literature, leading to a higher electron affinity and conductivity of the graphenic network.

The wafer-scale integration of graphene is of great importance in view of its numerous applications proposed or underway. A good graphene–silicon interface requires the fine control of several parameters and may turn into a high-cost material, suitable for the most advanced applications. Procedures that can be of great use for a wide range of applications are already available, but others are to be found, in order to modulate the offer of different types of materials, at different levels of sophistication and use. We have been exploring different electrochemical approaches over the last 5 years, starting from graphene oxide and resulting in graphene deposited on silicon-oriented surfaces, with the aim of understanding the reactions leading to the re-establishment of the graphene network. Here, we report how a proper choice of both the chemical environment and electrochemical conditions can lead to a more controlled and tunable graphene–Si(111) interface. This can also lead to a deeper understanding of the electrochemical reactions involved in the evolution of graphene oxide to graphene under electrochemical reduction. Results from XPS, the most suitable tool to follow the presence and fate of functional groups at the graphene surface, are reported, together with electrochemical and Raman findings.

Perovskite have had a great impact on the solid-state physics world in the last decade not only achieving great success in photovoltaics but, more recently, also in the implementation of other optoelectronic devices. One of the main obstacles for the adoption of Pb-based perovskite technologies are the high amounts of Pb needed in the conventional preparation methods. Here we present for the first time a detailed analysis of the photophysical and photoelectrochemical properties of CsPbBr3 films directly grown on fluorine-doped tin oxide (FTO) coated glass through a novel technique based in the electrodeposition of PbO2 as CsPbBr3 precursor. This technique allows to save up to 90 % of the Pb used compared to traditional methods and can be scalable compared with the commonly used spin-coating process. The low temperature analysis of their photoluminescence spectra, performed in both steady state and time dependence, revealed a strong interaction between electrons and longitudinal optical (LO) phonons dominant at high temperatures. On the other hand, the electrochemical and photoelectrochemical analysis proves that CsPbBr3 prepared using this new method has state-of-the-art features, showing a p-type behavior under depletion regime. This is also confirmed by photoelectrochemical measurements using p-benzoquinone as target molecule. These results prove that the proposed method can be used to produce excellent CsPbBr3 films, saving much of the lead waste.