Electroplating is a key process in many industrial fields such as automotive, electronics and decorative applications; this process makes it possible to provide new properties to substrates materials such as corrosion resistance, hardness and aesthetic value. Nonetheless, electroplating is considered one of the most non-sustainable industries related to the manufacturing sector, from both an environmental and a social point of view. With the approaching deadlines set by the United Nations for the 2030 Agenda, electroplating companies have started a trend of innovating their production processes with a focus on sustainability, acting on several fronts: performing simulations to predict criticalities and optimize working procedures, reducing the material used and recovering it from processing water. The purpose of this communication is to highlight the state of the art of sustainable practices peculiar to the electroplating industry, critically analyzing ongoing challenges to achieve and exceed the targets set by regulatory agencies. Both atomistic and multiphysics simulations will be analyzed as powerful tools to design both new sustainable formulations and items; then, the problem of metal dispersion will be discussed, evaluating different industrial approaches; finally, the focus will be shifted towards the general procedures to recover metal from wastewater.

In this study, we investigate the electrodeposition of various metals on silicon. Mn, Co, Ni, Ru, Pd, Rh, and Pt were identified as promising candidates for controlled electrodeposition onto silicon. Electrochemical evaluations employing cyclic voltammetry, Scanning Electron Microscopy (SEM) associated with energy-dispersive X-Ray Spectroscopy (SEM-EDS), and X-Ray Photoelectron Spectroscopy (XPS) techniques confirmed the deposition of Pd, Rh, and Pt as nanoparticles. Multi-cycle charge-controlled depositions were subsequently performed to evaluate the possibility of achieving tunable electrodeposition of nanostructured rhodium on n-doped silicon. The procedure increased surface coverage from 9% to 84%, with the average particle size diameter ranging from 57 nm to 168 nm, and with an equivalent thickness of the deposits up to 43.9 nm, varying the number of charge-controlled deposition cycles. The electrodeposition of rhodium on silicon presents numerous opportunities across various scientific and technological domains, driving innovation and enhancing the performance of devices and materials used in catalysis, electronics, solar cells, fuel cells, and sensing.

A thin film material obtained by Mn As co-electrodeposition was electrochemically deposited. Electrodeposition was chosen because is a versatile and easily scalable technique with low costs, and achievable under ambient conditions in water solution. These advantages are often unmatched by the typical production routes of spintronic materials. The use of different substrates was investigated, and the optimal deposition conditions were sought to reach the required morphology and composition, considering also the influence of pH and O₂. The deposition conditions were optimized using multivariate analysis. The samples were characterized morphologically, crystallographically, and compositionally with SEM-EDS, XRD, and XPS, suggesting that the deposit chemical composition was predominantly constituted by MnAs and MnO₂. Magnetic characterization performed with a SQUID magnetometer showed that the sample disclose a ferromagnetic component. MnAs and MnO₂ are known to have properties suitable for applications in spintronics, making this system interesting as an alternative for spintronic-based devices.

The electrodeposition of nanostructured materials onto silicon substrates offers a pathway to blend the advantageous traits of metals with silicon's exceptional electronic properties. This amalgamation facilitates the creation of integrated circuits, electrodes for batteries, supercapacitors, fuel cells, sensors, and photovoltaic cells [1]. This deposition method was selected for its cost-effectiveness, scalability, and rapid synthesis capability. It operates at room temperature and atmospheric pressure, utilizing aqueous solutions with adjustable properties. In this study, we examined the feasibility of electrodeposited nanoparticles, ultra-thin films, and Under Potential Deposition (UPD) on n-doped silicon [2]. The initial metal selection for electroplating was based on Density Functional Theory (DFT) calculations, considering factors such as the Schottky barrier, metal-silicon interactions, and metal-metal formation energy. Voltammetric analyses were conducted using solutions containing Ni, Ru, Pd, Rh, Pt, Ag, Mn, Co, and Au. Charge-controlled depositions were executed, supplemented by tests on electroless deposition. Optimal deposition conditions were sought for the most promising metals. The resulting deposits were morphologically and compositionally characterized using Scanning Electron Microscope (SEM) techniques, complemented by analytical spectroscopy including Energy Dispersive X-ray Spectroscopy Analysis (EDS) and X-ray Photoelectron Spectroscopy (XPS). Multiple charge-controlled deposition cycles were carried out to modulate the surface coverage, the average thickness, and the particle size distribution. The metal deposits thus obtained are under study to be used as promising templates to partially wet etching the underneath silicon and produce silicon nanowires (NWs). This procedure could create new opportunities for small-size and better-performing sensors [3]. Project funded under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.3 - Call for tender No. 341 of 15 March 2023 of Italian Ministry of University and Research (MUR) funded by the European Union - NextGenerationEU - Project code PE_00000004, CUP B83C22004890007, Project title "3A-ITALY - Made-in-Italy circolare e sostenibile". References [1] Giurlani, Walter, et al. Nanomaterials 12.4 (2022): 610, 10.3390/nano12040610 [2] Sulka, Grzegorz Dariusz. Molecules 28.10 (2023): 4040, 10.3390/molecules28104040 [3] Leonardi, Antonio Alessio, et al. Journal of Materials Science: Materials in Electronics 31 (2020): 10-17, 10.1007/s10854-018-0417-y

The progressive depletion of fossil reserves and the increase in energy demand have led to a rise in fuel and electricity prices highlighting the urgent need for an alternative energy strategy. This major problem is closely related to the increasing demand for critical raw materials [1]. These materials are crucial for the implementation of many industrial processes including electric mobility and electroplating industry. In this scenario, waste management and clean energy production are an inescapable binomial for the sustainability of all human activities and development [2]. This work reports a new strategy for obtaining low-content PGMs carbon-based electrocatalysts by recovering precious metals from industrial wastewater and promoting the development of a circular economy, specifically from the electroplating industry. The two materials Carbon black (CB) and graphene (G1) were functionalized with a pyrimidine tren derivative capable of complexing Pd(II) and results show that functionalization of CB and G1 dramatically increases the recovery rate. With the proposed methodology we obtained novel Pd functionalized carbon materials that are promising candidates for use as catalysts for the ORR in alkaline fuel cells. The catalysts were characterised through spectroscopic and electrochemical techniques including Scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and linear scanning voltammetry (LSV). Rotating ring electrode measurements (RRDE) were performed to investigate the ORR catalytic pathway and determine the number of electrons exchanged per oxygen molecule [3]. The results confirm that the tested materials support the 4 e- reaction pathway and reduce the formation of hydrogen peroxide. The approach used promotes the development of a circular economy and provides a basis for further development to improve the efficiency of future low-cost catalysts for alkaline fuel cells. The project FUTURO, 2022NW4P2T CUP B53D23013890006 PRIN2022 funded by the Italian Ministry of University and Research and NextGenerationEU is gratefully acknowledged. We also thank the EPSRC (UK) for funding through capital infrastructure grant EP/S033394/1. [1] T. Michałek, V. Hessel, M. Wojnicki, Production, Recycling and Economy of Palladium: A Critical Review, Materials 17 (2023) 45. https://doi.org/10.3390/ma17010045 [2] W. Giurlani, G. Pappaianni, F. Biffoli, E. Mariani, M. Bonechi, L. Giliberti, M. Tufarelli, P. Franzo, E. Cianfanelli, M. Innocenti, What Is the Current State of Sustainability in the Decorative Electroplating Industry? A Close Look at New Practices and Advances, Sustainability 16 (2024) 5821. https://doi.org/10.3390/su16135821 [3] V. Monini, M. Bonechi, C. Bazzicalupi, A. Bianchi, P. Gentilesca, W. Giurlani, M. Innocenti, A. Meoli, G.M. Romano, M. Savastano, Oxygen reduction reaction (ORR) in alkaline solution catalysed by an atomically precise catalyst based on a Pd( ii ) complex supported on multi-walled carbon nanotubes (MWCNTs). Electrochemical and structural considerations, Dalton Trans. (2024) 10.1039.D3DT03947A. https://doi.org/10.1039/D3DT03947A

Resorcinol polymerization is a quite important chemical reaction, also in connection with applicative aspects related to the production of industrial resins [1]. In this work, we studied the electrochemical oxidation of resorcinol on platinum, palladium and glassy carbon (GC) electrodes. We propose an oxidation-polymerisation mechanism for the resorcinol molecule, which is based on the Kane-Maguire polymerization scheme. The results of an exhaustive electrochemical characterization are integrated with the outcome of complementary chromatographic analytical techniques: LC-DAD (high performance Liquid Chromatography, equipped with Diode Array Detector) and LC-MS (mass-spectroscopy by means of Ion Trap mass analyzer). We demonstrate that upon electrochemical oxidation, resorcinol polymerizes following an efficient and facile process and an organic film is obtained on the electrode surface. We used cyclic voltammetry (CV), and a three-electrode cell to perform electrochemical oxidation. Then we used LC-DAD and LC-MS to study the intermediates involved in the electro-polymerization of resorcinol. Electrochemical experiments were performed under different condition of pH and solvent. CVs in a 0.5M H₂SO₄ solution shows an irreversible oxidation peak at 1.0 V that is pH dependent, consistent with a one-proton, one electron oxidation reaction. Applying potentials higher than the oxidation potential we obtained an organic film adhering to the electrode surface [2]. The polymer film was characterized by atomic force microscopy (AFM) and Scanning Electron Microscopy combined with Energy-Dispersive X-ray spectroscopy (SEM-EDS). We also perform a theoretical study on the first steps of resorcinol electro oxidation using ab-initio quantum mechanical based methods and molecular dynamics analysis (DRC algorithm) at the B3LYP/6-31G(d) and B3LYP/cc-pVTZ level of theory [3]. The resorcinol polymerization is considered to proceed via the dissociation of one (or two) hydrogen atom to form C-C and C-O dimers. The proposed mechanism for the resorcinol electrochemical oxidation is fully consistent with experimental results. Moreover, the film obtained on the electrode surface could be a potential substrate for electrodepositions or electroless deposition of metals and could be a promising candidate for the development of new materials of technological and industrial interest. [1] Formaldehyde and Phenol-Resorcinol-Formaldehyde Condensation Reactions: A Theoretical Study. Polymers 2017, 9, 426, doi:10.3390/polym9090426. [2] Bonechi, M.; Giurlani, W.; Stefani, A.; Marchetti, A.; Innocenti, M.; Fontanesi, C. Resorcinol Electropolymerization Process Obtained via Electrochemical Oxidation. Electrochimica Acta 2022, 428, 140928, doi:10.1016/j.electacta.2022.140928. [3] Bonechi, M.; Innocenti, M.; Vanossi, D.; Fontanesi, C. The Fundamental and Underrated Role of the Base Electrolyte in the Polymerization Mechanism. The Resorcinol Case Study. J. Phys. Chem. A 2021, 125, 34–42, doi:10.1021/acs.jpca.0c07702.