Electrochemical Deposition Research Articles

Transient Chemo-Mechanical Model of Lithium Plating Impacted by External Pressure

To meet the ever-growing need for high capacity, fast-charge batteries, lithium anodes have been considered a direct upgrade to previous commercial anode materials thanks to their high gravimetric density and low coulombic efficiency. However, their implementation into crucial applications such as electric vehicles has been hindered by safety issues during and at the end of their operational lifetime. Over hundreds of cycles, nonhomogeneous plating and stripping of lithium on the anode surface encourages the growth of dendrites, which eventually lead to capacity loss, cell failure, and fire. The application of stack pressure has been found to mitigate dendrite growth to an extent; however, the impacts of long-term pressure application on lithium deposition, and subsequent lithium plastic deformation and creep, are not well understood. In this work, we present a novel method for accurately modeling the interplay between mechanical deformation and electrochemical deposition. We develop a 3D, finite-element, transient model of lithium plating and stripping at the mesoscale. A stack pressure is applied to a lithium anode in contact with a polymer separator, and the electrochemical response to an applied current density is evaluated. The lithium protrusion is then reshaped to model incremental plating or stripping, thus simulating the cumulative interfacial movement over a full charge-discharge cycle. Mechanical complexities of the materials, such as lithium plastic deformation and separator porosity, are accounted for. The interfacial response is studied with respect to applied stack pressure and assumed lithium yield strength. Through this work, the impacts of stack pressure on dendrite growth at the microscale are explored. The lithium yield strength assumption is found to be crucial for accurately predicting deposition behavior.Supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.

Electrodeposition of WO3 Nanoparticles Onto a Carbon Membrane Surface for the Development of a Hybrid Filtration/Photocatalysis System

This study proposes the development of a photoactive filtration membrane using carbon fiber (CF) modified with an n-type semiconductor (WO3) to create a hybrid filtration/photocatalysis system applied in water treatment for simultaneous retention and degradation of the emerging contaminant (Sertraline - SER). The membrane was prepared through chemical electrodeposition in a three-electrode electrochemical cell, utilizing CF as the working electrode, two-dimensionally stable anode counter electrodes (De Nora), and an Ag/AgCl 4.0 mol L-1 KCl reference electrode. The preparation conditions included: 5.0 mmol L-1 of Na2WO4, 0.075% (v/v) H2O2, pH 1.4, with a potential of -0.5 V applied for 1 h, followed by heat treatment at 450 °C.Characterizations revealed a mesoporous structure, with UV-Vis absorption (300 - 700 nm), a band gap of 3.6 eV, and a BET surface area of 3.1 m2 g-1. Micrographs illustrated the formation of a uniform layer of WO3 on the CF surface, and characteristic peaks of C and WO3 in the monoclinic phase were confirmed. XPS analysis assigned species, including C 1s, O 1s, W (4f, 4f7/2, 4d5/2 4d3/2), with an intense peak at 530 eV related to the metallic bond (W-O).The optimized experimental conditions: SER 2.0 mg L-1, volume 100 mL, flow rate 180 mL min-1, pH 5.6, UV LED irradiation, complete removal of SER was observed in 30 min when applied to real effluents from a water treatment plant before and after the chlorination step. Additionally, complete degradation was achieved after 90 min of the experiment in simulated effluents in Milli-Q water. The photoactive membrane proved effective under various conditions, achieving 1.41 mg L-1 SER degradation after five reuse cycles and complete SER degradation after 40 min under solar irradiation. Experiments with scavenger agents confirmed the participation of species (HO•, O2 •-, 1O2, h+, and H2O2) in the degradation process. Additionally, six degradation products were identified with mass-charge (m/z) of 176, 189, 191, 273, 293, and 322, generated from hydroxylation, demethylation, and dechlorination reactions.The photoactive membrane has shown excellent potential for applications in filtration processes, mitigating issues associated with fouling. It facilitates the rapid removal and effective degradation of pollutants while also allowing for its application under various irradiation conditions. This feature simplifies and enables effective management in the treatment of contaminated waters.

(Henry Linford Award) Overcoming Challenges in Teaching Electrochemical Engineering

Electrochemical engineering is a highly interdisciplinary topic, requiring some preliminary knowledge of chemistry, material science, transport, kinetics, and process design. The major challenge in teaching the topic is that unlike most classes, where all students are ‘in-step’ in terms of their preparation, electrochemical engineering courses typically draw students from different disciplines (e.g., chemical engineering, chemistry, material science, biomedical engineering) with different background and preparation. This problem is further exacerbated in teaching electrochemical engineering short courses, which are typically attended by practicing engineers having quite different backgrounds, experience levels, and interests.When first encountering these issues, I thought that the best approach is to start from the basics, and obtain, through detailed mathematical derivations, very convincingly, the relevant equations. I could not be more wrong: students quickly lost interest, and the practical significance was often missed. I found out, that it is much more effective to first describe the issues and relevancy of the topic, and then, while still emphasizing the fundamentals, only outline the detailed derivations and skip to the final results, explaining the assumptions and limitations, while focusing on the applications and use. The students were still given class notes detailing the derivations and were directed to appropriate book chapters and publications for further reading.In terms of course content, I followed my admired and memorable teacher, Charles Tobias, who first introduced me, and so many others, to electrochemical engineering. Starting with ionic conduction and transport, and moving on to electrochemical thermodynamics, overpotentials, current distributions, multi-components and alloy deposition, transient effects, and scaling. Each topic was accompanied by relevant examples and homework problems which were later reviewed in class. I found out that it was not an effective use of class time to provide detailed discussion of specific electrochemical process technologies, which the students could read about in textbooks. Consequently, just one class period was devoted for brief discussion of each of the following: batteries and fuel-cells, electroplating, electrowinning and electrorefining, electrolytic processes, and corrosion. Emphasis was placed on discussing the fundamentals, issues, and major challenges for each. Students had the opportunity for in-depth study of additional specific applications by preparing and presenting in class a term-paper. To minimize direct reproduction from the literature, students had to indicate and discuss relevancy to fundamentals studied in class. Students could select their own topics and thereby relate the class material to their own disciplinary interests.To foster critical thinking and discussion, and to integrate the material taught, comprehensive case studies were presented and discussed in class. These case studies included among others, topics related to my own research, including scaling analysis, roughness evolution and dendritic growth, bottom-up plating of semi-conductor interconnects, and periodic reverse plating. These will be discussed in the oral presentation in more detail.I would like to conclude by thanking all my former students, who enriched my life so much, and whom I treasure as my ‘academic family’. Lastly and very importantly, I thank my dear friends and colleagues at Case Western Reserve University who made my teaching and research there most enjoyable, through stimulating discussions and close friendships.

Partial Applicability of Mixed Potential Theory in Unsteady Regime for Cu Electroless Deposition on Pt

Electroless deposition (ELD) has been practiced over many decades, but its underlying mechanism is incompletely understood. We explore the applicability of Mixed Potential Theory (MPT) in the unsteady regime during the electroless copper deposition (ELCD) on Pt surface pretreated by dipping Pt in SnCl2 and PdCl2. We demonstrate that ELCD occurs in the low and high potential zone (LPZ & HPZ) at two different reaction rates due to the under-potential deposition of Cu on pretreated Pt in LPZ. The Nyquist plot in HPZ shows one semicircle, while LPZ shows two semicircles. Single semicircle in HPZ suggests dependency only on catalytic potential available on the surface over which ELCD occurs. The two semicircles in LPZ indicate that besides the surface catalytic potential, the dependency is on the reaction intermediate of formaldehyde oxidation, limiting the relevance of MPT. MPT posits that reduction and oxidation in Cu ELD are independent of each other and the role of the surface is only in establishing the catalytic potential. To check the pertinence of MPT, we obtained the polarization resistance (RP) from the Nyquist plot of (a) ELCD solution, (b) CuSO4 with Tartrate and without Formaldehyde i.e. electrochemical copper deposition (ECCD). The RP so obtained shows a significant difference only in LPZ but not in HPZ because of which we argue that MPT is applicable only in the HPZ.

New Hybrid Materials Based on N-Doping Copolymers of Thiophene Derivatives for Electrochemical Energy Storage

Over the past decade, electroactive conducting polymers (ECPs) are among the most potential pseudocapacitive materials for the electrodes of microsupercapacitors. ECPs exhibit several advantages, such as good conductivity (up to 103 S cm-1), flexibility, high specific capacitance (values ranging from 300 to 800 F.g-1 depending on synthesis and electrochemical performance conditions), relatively cheap and ease of synthesis [4]. Therefore, the electrochemical deposition of ECPs revealed a new strategy to design a great variety of various polymer morphologies as an innovative pseudocapacitive materials. Based on the different storage mechanism, electrochemical supercapacitors can be divided into three types, namely electrochemical double layer capacitors (EDLCs), pseudosupercapacitors and hybrid supercapacitors in which ECPs and other pseudocapacitive materials such as carbon materials, transition metal oxides, nitride complexes allow to store higher amount of capacitance per gram (faradic reactions) than EDLCs (pure capacitive energy storage reaction).In this work, we have elaborated new n-doped conducting polymers Poly[3,6-bis(2-thienyl)pyridazine] and Poly[3,6-bis(2-(3-n-hexylthienyl))pyridazine] by making electropolymerization on Pt disk electrode and 3 nm alumina coated silicon nanowires in acetonitrile organic electrolyte. The comonomers 3,6-bis(thienyl)pyridazine and (3,6-bis(2-(3-nhexylthienyl))pyridazine) have been successively synthesized. The produced polymeric materials Poly[3,6-bis(2-thienyl)pyridazine] and Poly[3,6-bis(2-(3-n-hexylthienyl))pyridazine] during n-doping process on Pt working electrode in acetonitrile solution of TBAPF6 (0.1 M) expose very low potential value of -2.23 V and -2.19 V at current density of -0.25 mA.cm-2 and -0.06 mA.cm-2, respectively. The elctropolymerization of synthesized comonomer 3,6-bis(thienyl)pyridazine has been done on Al2O3@SiNWs and resulted in thin layer of polymer film with micropores. The experimental results are compared to electropolymerization study of thiophene monomer on Pt disk and Al2O3@SiNWs electrodes to highlight the similarities and electrochemical advancements.

3D-Printed Hierarchical Electrodes for Ampere-Level Alkaline Water Electrolysis

In the realm of water electrolysis technology, Alkaline Electrolysis Cell (ALK) hydrogen production stands as a pivotal technology, playing a critical role in the pursuit of large-scale green hydrogen production and the achievement of the "dual carbon" objective. Despite its importance, the mass transfer efficiency of commercial porous nickel electrodes currently used in ALK systems is suboptimal. These electrodes, plagued by unstable catalyst loading, typically operate at current densities between 300-500 mA/cm², seldom reaching the desired threshold of 1 A/cm². This limitation hampers the potential of ALK hydrogen production to satisfy industrial-scale hydrogen production demands.In the quest to overcome these limitations, the concept of the Triple Periodic Minimum Surface (TPMS) structure, a cellular architecture mathematically defined and prevalent in natural biological forms such as butterfly wings and beetle shells, is introduced. The TPMS's unique geometry is adept at adapting to mechanical requirements for various applications, including structural and fluidic systems. It allows for versatile manipulation of geometric parameters like aperture size, porosity, and tortuosity, thereby substantially broadening the design possibilities for electrode structures and enhancing the efficiency of gas-liquid and electron transfer.To harness these benefits, we propose the creation of nickel/nickel-iron electrodes using 3D printing technology. These electrodes are characterized by their cross-scale porosity, ordered structure, and adjustable TPMS design. This innovative electrode design significantly augments bubble transport efficiency and mass transfer performance, while also providing additional anchor points for catalysts, thereby enhancing the electrochemical active surface area, intrinsic activity, and stability of the composite catalyst. As a result, these electrodes achieve ampere-level current densities in ALK electrolysis cells, enhancing electrolysis efficiency and reducing energy consumption.Our methodology involves the use of selective laser melting printing technology to fabricate multi-tier nickel/nickel-iron electrodes of varying specifications. These electrodes are then coated with MOOH catalysts using an electrochemical deposition process. Through rigorous testing and comparison of electrochemical performance parameters, we identified the optimal multi-stage nickel/nickel-iron electrode and its composite catalyst.Electrochemical performance tests reveal that, compared to traditional commercial porous nickel electrodes, our 3D printed electrodes decrease overpotential by 14% and improve electrolytic cell efficiency by 10% at a current density of 1 A/cm². Furthermore, these electrodes exhibit minimal degradation after a 500-hour durability test. The demonstrated efficiency and durability of these 3D-printed hierarchical electrodes indicate significant potential for their application in ampere-level alkaline water electrolysis. Figure 1

Prominent Enhancement of Nonlinear Optical Absorption in SnS2 Nanosheets through Controllable Electrodeposition of Porphyrins

AbstractConstructing organic‐inorganic composites presents a promising approach to enhance the nonlinear optical (NLO) response of materials. However, the effectiveness of this approach is impeded by the complexity of synthesis procedures and challenges in controlling the loading amount. Herein, a convenient and controllable electrodeposition method to non‐covalently combine SnS2 with tetracationic porphyrin (TMPyP) and the remarkable enhancement in NLO absorption of the resultant composite, are introduced. Through this method, a series of SnS2/TMPyP thin films are synthesized, allowing for the regulation of porphyrin loading via varying the deposition time. These resultant SnS2/TMPyP composites exhibit prominent nonlinear absorption coefficients when subjected to femtosecond laser irradiation of varying wavelengths. Notably, the compound with an electrochemical deposition time of 30 s achieves the largest third‐order nonlinear absorption coefficient of 6155 ± 243 cm GW−1 under 800 nm laser excitation, marking an 8.9‐fold increase compared to pristine SnS2 nanosheets. Based on the staggered energy level structure between TMPyP and SnS2, effective enhancement of charge separation/transfer is achieved by leveraging the unique π‐conjugated groups of porphyrins, which facilitates the NLO process and improves the NLO performance of films.

Enhancement in the Stability of Porous Silicon Using Electrochemical Grafting of Polymer 2,6 Dihydroxy Naphthalene

While there have been many advancements related to porous silicon, the reactivity of silicon with the ambient (particularly in environments with oxygen and humidity) has limited its use and integration in a wide variety of applications. Therefore, it is important to passivate the surface of nanostructured/porous silicon. To this end, there have been many reports in literature where passivation of bare (or unpassivated) porous silicon (UPSi) surface has been performed using gas phase techniques (thermal carbonization) and solution-based methods. In this work, we have studied the influence of the electrochemical deposition of polymer 2,6 dihydroxynaphthalene (2,6 DHN), in enhancing the stability of porous silicon surfaces.Porous silicon was synthesized by the electrochemical etching of pre-cleaned p-type silicon substrates with resistivity of about 0.001 Ω-cm to 0.005 Ω-cm, in a PTFE cell that we have fabricated, with 48% HF and ethanol mixture (7:3) as the electrolyte solution, at a current density of about 1.08 A/cm². The polymer solution used for electrodeposition was prepared as a solution of 1 mM 2,6-dihydroxy naphthalene (2,6-DHN) in 100 mL of 1x phosphate buffer solution, which was vacuum infiltrated in the synthesized porous silicon and electrodeposited on the same with the standard three electrodes chronopotentiometry method, at a constant current density of about 2 mA/cm² for 120 seconds. Electrodeposited porous silicon was kept on the hot plate for 10 min at 220℃, followed by a thermal treatment at 600℃, for 180 min, in the presence of N2 flow (1 L/min).The surface morphology of the unpassivated porous silicon (UPSi) and passivated porous silicon (PPSi) are shown in the insets of Fig. 1(a) and (b), respectively. This suggests the presence of an incredibly thin coating of the polymer on the pore walls. The pores in, both, unpassivated and passivated porous silicon samples (UPSi and PPSi) remained open and unobstructed, offering a uniform distribution of pores with sizes ranging between 5 nm and 20 nm.To perform a corrosion test of the UPSi and PPSi, we look at these layers after they have been exposed to 1 M NaOH aqueous solution, for different time durations. We have seen the formation of a spontaneous bubble on the surface of the UPSi sample during the test. To this end, we have observed visible and morphological changes of both UPSi and PPSi samples after the corrosion stability test for 5 seconds and 120 minutes, respectively, as seen in Fig. 1(a) to (h). Due to the very high internal area and the hydrogen-terminated surface, in an aqueous solution, UPSi is oxidized by water at room temperature and degrades. In comparison, the PPSi sample is stable for more than 120 minutes.Electrochemical characterisation of UPSi and PPSi was performed in a 10 mM NaCl aqueous electrolyte with a three-electrode cyclic voltammetry (C-V) setup. C-V measurements of the UPSi sample show strong redox reaction in the potential window of 0 V to 1 V, whereas, the PPSi sample shows a nearly constant charging current response in the potential window of -1 V to 1 V, as shown in Fig. 1(i). These results emphasize that the passivation of porous silicon using 2,6 DHN polymer makes it more stable and less reactive in an aqueous medium. Figure 1

The Role of Iron Impurities on Nickel Cathodes for Hydrogen Evolution Reaction (HER)

Over the last decades, several studies have reported the effect of traces of iron species on the improvement of the oxygen evolution reaction (OER) kinetics for nickel-based anode materials in alkaline media. [1] However, the effect of iron impurities on the hydrogen evolution reaction (HER) is still a subject to debate. For instance, at low iron concentrations (0.03 – 0.5 ppm) a loss of the HER activity for Ni surface is observed due to the electrochemical deposition of less active Fe. [2,3] Other studies showed less deactivation behavior of the Ni cathode at 3 and 14 ppm iron ion concentration over time. [2,4] This improvement of the lifetime of the Ni electrode in the presence of iron cations is very likely related to the increased surface roughness by Fe electrodeposition and thereby the decrease in the formation of inactive NiH species. [2] Systematic investigations on Fe sputtered Ni surfaces with different coverages showed that ≥ 60% of Fe coverage stabilizes the Ni cathode by preventing hydrogen diffusion through the Ni lattice at constant current density of -100 mA cm-2. [5] Generally, the role of Fe impurities on the HER activity for nickel cathode surface in alkaline environments is still unclear to date.In this work, we comprehensively evaluated the influence of the iron ion concentration on the long-term HER performance for a polycrystalline Ni electrode by using rotating disc electrode (RDE) setup. The changes in HER activity as a function of the iron ion concentration was correlated with resulting surface roughness and layer thickness/coverage of the electrodeposited iron. Highly purified 0.1 M KOH was used as basic electrolyte solution and mixed with iron ion concentrations in the range of <1, 6 and 14 ppm. The initial HER activity on the Ni surface is unchanged irrespective of the iron ion concentration added into the electrolyte. However, at iron ion concentrations of <1 ppm and 6 ppm, the chronopotentiometric (CP) experiments at -10 mA cm-2 for 24 hours show a potential drop of ~70 mV and ~53 mV, respectively, resulting in a deactivation of the Ni surface by forming NiH species. Very interestingly, high iron ion concentrations (e.g. ~14 ppm) lead to an almost constant potential (~ 1 - 7 mV drop) during the CP experiment, by reducing the formation of inactive NiH. The electrochemically treated Ni electrodes were then characterized by X-ray fluorescence spectroscopy (XRF) and scanning electron microscopy in combination of energy dispersive X-ray spectroscopy (SEM-EDX). The SEM micrographs show iron particles electrodeposited uniformly on the polycrystalline Ni surface after the CP experiments with < 1, 6 and 14 ppm of iron ion concentrations in 0.1 M KOH. The analysis of the EDX maps reveals a coverage of 17, 54 and 58 % on the Ni surface at iron ion concentrations of < 1, 6 and 14 ppm, respectively. Obviously, iron ion concentrations of 6 and 14 pm show very similar coverages on the Ni surface, indicating their minor role on the HER activity. We suggest that during the HER the hydrogen bubbles suppress the formation of a dense and complete iron layer on the Ni electrode surface. The spatial distribution and thickness of the electrodeposited Fe particles were also evaluated after 1 h and 24 h of CP experiments with < 1, 6 and 14 ppm iron ion concentrations by using micro-XRF equipped with a polycapillary lens of 20 µm. Thicker iron layers after 24 hours are formed at high iron ion concentrations, preventing the hydrogen diffusion into Ni lattice to form inactive NiH species and to maintain the HER activity over time under alkaline conditions.In summary, we show that traces of iron impurities have a huge impact on the long-term durability of polycrystalline Ni electrodes for HER in alkaline environments. A critical iron ion concentration is required to suppress the formation of inactive NiH species during the HER at -10 mA cm-2 for 24 h and/or to electrodeposite enough iron for maintaining the HER kinetics on the polycrystalline Ni electrodes in alkaline environments.

Treatment of Se-Impacted Wastewater Using a Three-Dimensional Packed Bed Electrochemical Reactor

Selenium is an essential element for flora and fauna in trace amounts. It plays a crucial role in bolstering photosynthesis and facilitating thyroid hormone metabolism. However, excessive consumption of selenium can result in health concerns such as reproductive complications and cancer. Selenium usually coexists with minerals such as copper and coal in the natural environment. The associated activities, such as copper mining and coal combustion, have greatly accelerated the mobilization of selenium. The selenium released through coal combustion is mostly captured in the flue gas desulfurization (FGD) wastewater as inorganic selenite and selenate.Our lab previously validated the viability of direct electrochemical reduction (SeDER) to remove dissolved selenite from a simplified FGD water matrix using planar gold and graphite cathodes, where more than 94% of the aqueous selenite can be converted to elemental Se(0) deposited on the cathode surface. Graphite is eventually selected for its low material cost, decent removal performance, and minimum secondary pollution as compared to gold and other non-noble metal cathodes. This direct electrochemical deposition process provides many benefits that existing biological and indirect electrochemical methods lack, such as zero chemical addition and low to zero solid generation. However, this method is only suitable for wastewater with elevated temperatures necessary to generate conductive Se(0) for continuous reduction. The inclusion of a heating process adds complexity to the design, impeding the scalability of the SeDER system. Furthermore, the application of SeDER is constrained to Se-impacted wastewater with an elevated temperature.In this study, we propose a novel reactor design utilizing electrochemical reduction to treat Se-impacted wastewater at ambient temperature. The electrodes we used are made of graphite for the reasoning stated above. The reactor consists of a pair of planar graphite anode and cathode, and the inner chamber is filled with cylindrical graphite particle electrodes (PEs) separated by a nylon spacer to create an anodic chamber and a cathodic chamber. The PEs act as an extension of the planar electrodes, which offers numerous reaction sites and minimizes the travel distance for selenite ions to reach the electrode surface. In our 120-mL batch test with 0.1-mM selenite in 100-mM phosphate buffer, the exact system without filler removed 0% selenite at room temperature, while the filled 3D system removed on average 50% of the selenite in 3 hours. Using the same 3D system, we then investigated performance enhancement with a recirculating operation. The total working volume is fixed at 200 mL, while the flow rate and the applied voltage vary. The flow rate is set at the values with hydraulic retention time (HRT) fixed at 15 min, 30 min, and 60 min. The system-applied voltage is set at -1.9V (just enough for selenite reduction), -2.1V, and -2.3V. We found that the shortest HRT combined with -2.1V system applied voltage yielded the highest selenite removal performance in all tests, with an average of 47% removal in 3 hours. We hypothesized that the shorter HRT provides a faster flow rate that refreshes the PE’s surface from insulative Se(0) deposition, which provides sustainable reaction sites for the incoming selenite. At -2.1V, the potential is negative enough to allow selenite reduction while fewer parasitic reactions (e.g., hydrogen evolution reaction) occur compared to that under -2.3V.With the selected system voltage and flow rate, we eventually explored competing ion behavior and switched from a simplified water matrix to simulated Se-impacted wastewater. We found that of all the commonly found competing ions (i.e., sulfate, nitrate, and chloride), chloride significantly impacts selenite removal, with performance dropping to 10% removal in 3 hours. Nitrate slightly decreased the selenite removal, with an average Se removal performance of 23%. Sulfate, on the other hand, resulted in an increase in selenite removal after addition. We hypothesize that a high sulfate concentration in simulated wastewater could help alleviate the repulsing force from the cathode surface for the selenite ions. The double layer of the PEs could also be compressed by the high ionic strength, which decreases the capacitance and promotes selenite reduction. To confirm this hypothesis, we conducted an electrochemical impedance study to analyze the effect of competing ions on reaction kinetics and capacitance. We also performed surface analysis for the wasted planar electrodes and PEs to investigate the change in morphology and observed possible chemical residue. These characterizations will help us develop a regeneration protocol in long-term operation and help us scale up our prototype to manage actual Se-impacted wastewater.

(Vittorio de Nora Award) When Solid State Semiconductor Physics and Devices Meet Photoelectrochemistry: From Growth and Interfacial Processes to Photovoltaics

I joined the CNRS solid-state physics laboratory near Paris in 1978, to work on the preparation of CdTe solar cells using close space sublimation (CSS) growth process. Thanks to some original discoveries, we were able to achieve a record yield of 10.5% for the time, but this research was gradually abandoned in France and in Europe. Yet it was this method that formed the basis of the technology developed with such success by first solar. So I was on the right track.However, it was in a different direction that I decided to go: semiconductor photoelectrochemistry, a rapidly developing field at the time. Here too, solar energy remained the backdrop, with the field opened up by Honda’s work on the photoelectrolysis of water. I thus began research into the mechanisms of charge transfer at semiconductor-electrolyte interfaces, keeping CdTe as my study material, enabling me to draw on my knowledge of solid-state devices to guide the analysis of its photoelectrochemical behavior in an original way. Our studies have focused on highlighting the energetic changes at interfaces under illumination during charge transfer reactions towards redox species in competition with corrosion reactions. We have demonstrated the role of adsorption and surface chemistry in these phenomena, with the result that photoelectrochemical properties can be optimized. Photoelectrochemistry is once again a highly topical field with artificial photosynthesis.In 1980 I discovered that CdTe layers could be deposited electrochemically in a simple beaker, as theorized by F.A. Kröger, without having to use much heavier vacuum processes.The electrochemical deposition of CdTe immediately became one of the major themes of my research, and remained so until the 2000s. The analysis of deposition mechanisms and their relationships to film properties were the subject of numerous publications and theses, with some outstanding results, in particular the synthesis of a new phase such as CdTe2, the study of as-grown semiconducting properties , the demonstration of epitaxial growth.This work gave rise to two major lines of research with far-reaching consequences. The first concerns the extension of electrochemical synthesis to other compound semiconductors of oxide type, with the discovery of the electrochemical synthesis of ZnO by cathodic reduction in the presence of oxygen, leading to materials of exceptional crystalline quality, suitable for epitaxial deposition. Depending on the experimental conditions, the forms obtained can range from nanocolumns to compact films. These results have opened a new avenue at international level. They led us to introduce them into the photovoltaic field for the formation of TCOs or hybrid matrices for dye cells. The second concerns the electrochemical synthesis of CuInGaSe2 (note CIGS), a ternary semiconductor of major industrial importance to photovoltaics. Initiated in the early 90s, this work involved both fundamental research and the creation of an industrial outlet. It led to the creation of a laboratory dedicated to photovoltaics with EDF in 2002, which succeeded in the creation of a start-up in 2009, NEXCIS, which achieved world-class performance in the field. This adventure has been the subject of a book chapter. Today, it continues with the creation of a new start-up, that I founded in 2021, that is using the electrodeposition technology to manufacture ultra-light, flexible, high-efficiency photovoltaic modules for new applications.This vision of the fundamental and underestimated interest of solution growth methods (electrochemistry or CBD) for the development of high-quality functional materials, particularly for photovoltaic conversion, has guided my entire scientific approach to date. The emergence of halogenated perovskite cells, also prepared in solution, has recently reinforced this approach as a way forward.Selected references:RECOMBINATION AND CHARGE-TRANSFER AT THE ILLUMINATED N-CdTe ELECTROLYTE INTERFACE - SIMPLIFIED KINETIC-MODEL ,LINCOT, D; VEDEL, J, JOURNAL OF ELECTROANALYTICAL CHEMISTRY 220 (1987) 179MECHANISM OF CHEMICAL BATH DEPOSITION OF CADMIUM-SULFIDE THIN-FILMS IN THE AMMONIA-THIOUREA SYSTEM - IN-SITU KINETIC-STUDY AND MODELIZATION, ORTEGABORGES, R; LINCOT, D, JOURNAL OF THE ELECTROCHEMICAL SOCIETY 140 (1993)3464.SOLAR-CELLS WITH IMPROVED EFFICIENCY BASED ON ELECTRODEPOSITED COPPER INDIUM DISELENIDE THIN-FILMS, GUILLEMOLES, JF; COWACHE, P; MASSACCESSI, S; THOUIN, L; SANCHEZ, S; LINCOT, D; VEDEL, J., Advanced Materials 6 (1994)379Mechanistic study of cathodic electrodeposition of zinc oxide and zinc hydroxychloride films from oxygenated aqueous zinc chloride solutions, Peulon, S; Lincot, D , JOURNAL OF THE ELECTROCHEMICAL SOCIETY 145 (1998)864Solution growth of functional zinc oxide films and nanostructures, Lincot, D., MRS BULLETIN 35(2010) 778From the Lab to Scaling-up Thin Film Solar Absorbers. Hariklia Deligianni, Lubomyr T. Roamnkiw, Daniel Lincot, Pierre-Philippe Grand. Book Chapter in Advances in Electrochemical Science and Engineering,XVIII (2018)

Revealing the Effects of Polymer Additives on Zn Dendrite Suppression in Aqueous Zn Batteries via in-Situ EC-AFM

Polyethylene glycol (PEO) is a commonly used polymer in the field of batteries for achieving flat and uniform electrodes to enhance the performance of batteries, such as lithium batteries and zinc (Zn) batteries. However, the impact of PEO on the electrochemical deposition of Zn metal on electrodes remains uncertain. In this study, we selected ZnSO4 solution as electrolyte and copper (Cu) substrates as electrodes, which are widely applied in Zn batteries. We used in situ electrochemical atomic force microscopy (EC-AFM) to observe the nucleation and growth of Zn metal plates on the Cu substrate in the presence of different concentrations of ZnSO4 and PEO additives. Our results indicate that PEO biases the crystallographic orientation of the initially deposited Zn metal nuclei, but does not have an obvious influence on subsequent growth. Based on our findings, we hypothesize that PEO primarily interacts with the Cu substrate to adjust the interfacial energy of the Cu-electrolyte interfaces. In contrast, due to the lack of apparent change in the Zn growth rate, we postulate that PEO does not affect the delivery rate of Zn2+ to the electrode surface. The consistent aspect ratio of the Zn plates combined with the lack of an effect on growth rates further suggests that PEO does not interact significantly with the surface of the newly formed Zn plates. The Zn metal will undergo surface reorganization in a mildly acidic aqueous solution as a result of oxidation of Zn, which is not affected by PEO adsorption. Our findings provide both insight into the underlying mechanism by which PEO promotes electrode flattening in Zn batteries and a standardized protocol for elucidating the impact of additives on the morphological evolution of interfaces during electrochemical deposition.Work by C.O. was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Electrochemical Quartz Crystal Microbalance Study on the Electrodeposition of Fe, Co and Fe-Co Alloys

Cobalt-iron alloys are interesting soft magnetic materials which are used for example in magnetic sensors and transducers. They can be obtained by different techniques such as PVD, magnetron sputtering, or casting. One easy and not very expensive way to produce these alloys is the electrochemical deposition technique, which was also chosen in this study.This contribution will describe the electrodeposition of Co, Fe and Fe-Co alloys (Fe70Co30) from an aqueous sulphate-based electrolyte containing boric acid as a buffer and sodium citrate and citric acid besides the metal sulphates. Potentiostatic step experiments and cyclic voltammetry were performed in parallel to electrochemical quartz crystal microbalance. Thus, we could identify the potential at which the deposition of the metals sets in, the mass of the deposited species as well as the current efficiency. We could also extract the partial current due to hydrogen evolution reaction and the partial current due to individual metal or their alloys from the total current density. The morphology and structure of the deposited films were investigated by means of SEM and XRD, respectively. The grain size of the deposits was calculated from the XRD data using Scherrer equation. Addition of citric acid to the electrolyte results in the smaller grain size of the deposited Fe-Co films.

CoP electrodeposited on TiO2 nanorod arrays as photoanode for enhanced photoelectrochemical water splitting

AbstractIt is of great significance to design photoelectrodes with high carrier separation and transport efficiency in photocatalytic water separation systems. In this study, we used a simple electrochemical deposition method to regulate the load of co‐catalyst CoP on TiO2 nanorods to improve the photoelectrochemical properties. The photocurrent density of TiO2/CoP (20) photoanode at 1.23 V increases to 1.57 mA/cm2, which is 3.4 times that of original TiO2. Long‐term photoelectrolysis reveals that this electrode has excellent stability. Mechanistic studies support the role of CoP nanoparticles in improving photoelectrochemical property and imply that the excellent photoelectrochemical property of TiO2/CoP photoanode is mainly ascribed to the suppress of surface photogenerated electrons and holes recombination due to the construction of built‐in electric field between TiO2 and CoP.

Novel Design and Synthesis of Ni-Mo-Co Ternary Hydroxides Nanoflakes for Advanced Energy Storage Device Applications

Three-dimensional interconnected mesoporous nanoflakes of amorphous Ni-Mo-Co trimetallic hydroxides were successfully deposited on a Ni foam (NF) using a facile, environmentally friendly, and scalable electrochemical deposition method. The elemental composition of the nanoflakes, including Ni2+, Mo6+, and Co2+, was characterized by X-ray photoelectron spectroscopy (XPS), while the morphology and particle size of the synthesized nanomaterials were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Ni-Mo-Co trimetallic hydroxides on NF were employed as binder-free electrodes for supercapacitors. The Ni-Mo-Co trimetallic hydroxides with a Ni/Mo/Co ratio of 1/1/0.4 exhibited outstanding long-term cyclability over 5000 cycles, with a high reversible specific capacitance of 2700 F g−1 and a high capacitance retention of 96.63% at 10 A g−1. Furthermore, they demonstrated excellent rate performance, maintaining a capacitance of 2429 F g−1 at a current of 50 A g−1, which corresponds to approximately 80% capacitance retention compared to the capacitance at 2 A g−1. The superior performance of these Ni-Mo-Co trimetallic hydroxides can be attributed to their mesoporous hierarchical architecture, which provides large open spaces between the interconnected nanoflakes, numerous electroactive surface sites, facile electron transmission paths, and the synergistic effects of the trimetallic components. These findings demonstrate that Ni-Mo-Co trimetallic hydroxides are promising electrode materials, offering both high capacitance and long-term cyclability for supercapacitors.

Research on solar cell preparation technology for cutting-edge technology

Flexible dye-sensitized solar cells are highly valued as a practical technology with low production costs. In this paper, we study flexible dye-sensitized solar cells consisting of nanocrystalline TiO2 thin-film electrodes based on titanium metal and counter electrodes based on conductive coated polymers. In order to improve the photoelectric conversion efficiency, nanocrystalline TiO2 film electrodes and TiO2 nanotube film electrodes based on titanium metal and TiO2 nanotube film electrodes are prepared by DC low-field electrophoretic deposition, electrochemical anodizing and screen printing under DC and pulse voltages combined with high-temperature sintering methods; and platinum-carrying counter electrodes and carbon counter electrodes based on conductive coated polymers are prepared by low-temperature techniques, such as constant-current electrochemical deposition and chemical reduction. The mechanisms and characteristics of different preparation methods and optimization techniques are analyzed and discussed, and the performances of nanocrystalline TiO2 thin film electrodes and counter electrodes prepared by different methods are compared. On this basis, the all-flexible solar cell is developed, and the maximum photoelectric conversion efficiency reaches 6.74%.

Photothermal Antibacterial and Osteoinductive Polypyrrole@Cu Implants for Biological Tissue Replacement.

The treatment of bone defects caused by disease or accidents through the use of implants presents significant clinical challenges. After clinical implantation, these materials attract and accumulate bacteria and hinder the integration of the implant with bone tissue due to the lack of osteoinductive properties, both of which can cause postoperative infection and even lead to the eventual failure of the operation. This work successfully prepared a novel biomaterial coating with multiple antibacterial mechanisms for potent and durable and osteoinductive biological tissue replacement by pulsed PED (electrochemical deposition). By effectively regulating PPy (polypyrrole), the uniform composite coating achieved sound physiological stability. Furthermore, the photothermal analysis showcased exceptional potent photothermal antibacterial activity. The antibacterial assessments revealed a bacterial eradication rate of 100% for the PPy@Cu/PD composite coating following a 24 h incubation. Upon the introduction of NIR (near-infrared) irradiation, the combined effects of multiple antibacterial mechanisms led to bacterial reduction rates of 99% for E. coli and 98% for S. aureus after a 6 h incubation. Additionally, the successful promotion of osteoblast proliferation was confirmed through the application of the osteoinductive drug PD (pamidronate disodium) on the composite coating's surface. Therefore, the antimicrobial Ti-based coatings with osteoinductive properties and potent and durable antibacterial properties could serve as ideal bone implants.

Nitrated benzothiadiazole-based D-A electrochromic polymers with tunable spectral properties

Nitrated benzothiadiazole (BT) is the promising acceptor units in constructing D-A-D electrochromic polymers, but its researches in the electrochromic field was very limited so far. In this work, four kinds of nitrated polymer precursors (Th-NO2-BT, EDOT-NO2-BT, Th-2NO2-BT, and EDOT-2NO2-BT) were synthesized by Stille coupling reaction with EDOT and thiophene units as the end groups (electron donor units) and mono-nitrated benzothiadiazole and di-nitrated benzothiadiazole as the core groups (electron acceptor units). The chemical structure and optical properties of the precursor were investigated by means of 1H NMR, UV–vis absorption and fluorescence spectra; the corresponding mono-nitrated polymer films were obtained in CH2Cl2-Bu4NPF6 system by electrochemical deposition method. The optical band gap of di-nitrated polymer precursor is obviously larger than the corresponding mono-nitrated polymer precursor (both ultraviolet and fluorescence spectra are obviously blue-shifted), accompanied with the obvious increased initial oxidation potential. Due to the fluorescence quenching effect of -NO2 group, their absolute quantum yields are all very low (0.0006–0.015). The spectroelectrochemistry and electrochromic kinetics of mono-nitrated polymer films (P(Th-NO2-BT) and P(EDOT-NO2-BT)) were studied. It was found that P(EDOT-NO2-BT) can show better electrochromic performance than P(Th-NO2-BT), with dark green in the neutral state and more obvious electrochromic performance in the near-infrared region (optical contrast: 38.4 %, coloration efficiency: 129.1 cm2/C, and fast response time: 1.4 s). This systematically study about the effects of nitro substitution effect on the properties of D-A electrochromic polymers, which will further expand the selection of the new acceptor units and the application prospect of nitrated electrochromic materials.

Copper(II)-Tannic Acid@Cu with In Situ Grown Gold Nanoparticles as a Bifunctional Matrix for Facile Construction of Label-Free and Ultrasensitive Electrochemical cTnI Immunosensor.

Sensitive detection of cardiac troponin I (cTnI) is of great significance in the diagnosis of a fatal acute myocardial infarction. A redox-active nanocomposite of copper(II)-tannic acid@Cu (CuTA@Cu) was herein prepared on the surface of a glassy carbon electrode by electrochemical deposition of metallic copper combined with a metal stripping strategy. Then, HAuCl4 was in situ reduced to gold nanoparticles (AuNPs) by strong reductive catechol groups in the TA ligand. The AuNPs/CuTA@Cu composite was further utilized as a bifunctional matrix for the immobilization of the cTnI antibody (anti-cTnI), producing an electrochemical immunosensor. Electrochemical tests show that the immunoreaction between anti-cTnI and target cTnI can cause a significant reduction of the electrochemical signal of CuTA@Cu. It can be attributed to the insulating characteristic of the immunocomplex and its barrier effect to the electrolyte ion diffusion. From the signal changes of CuTA@Cu, cTnI can be analyzed in a wide range from 10 fg mL-1 to 10 ng mL-1, with an ultralow detection limit of 0.65 fg mL-1. The spiked recovery assays show that the immunosensor is reliable for cTnI determination in human serum samples, demonstrating its promising application in the early clinical diagnosis of myocardial infarction.

Label free and ultrasensitive electrochemical detection of carcinoembryonic antigen using a disposable aptasensor based on Pd and graphene

We prepared an electrochemical aptasensor for label-free analysis of carcinoembryonic antigen (CEA). Herein, PdNPs were synthesized on the surface of graphene-modified screen-printed carbon electrodes (Pd-GN/SPCE) via electrochemical method for immobilisation of CEA aptamer as a bio-recognition element. The morphological characterizations of the fabricated Pd-GN/SPCE were performed using SEM, EDX, and elemental mapping that confirmed the successful electrochemical deposition of PdNPs. A disposable aptasensor for ultrasensitive electrochemical measurement of CEA was proposed by immobilising CEA aptamer on Pd-GN/SPCE. The electrochemical measurements were performed using 5 mM [Fe(CN)6]3-/4- as a redox probe. The electrochemical deposition of PdNPs improved the electrical conductivity resulting in enhanced current response for the redox probe. When CEA antigen interacts with CEA aptamer, it reduces the oxidation and reduction current of [Fe(CN)6]3-/4- due to the attachment of biomolecules to the electrode surfaces that hinders the electron transfer. The current changes of the redox species before and after CEA binding were measured using DPV. The developed aptasensor possessed a wide calibration range of 0.002–200 ng/mL and detection limit of 1.0 pg/mL. The aptamer-immobilised electrode provides an exceptional selectivity, reproducibility, and sensitive measurement of CEA. Moreover, the effective sensing of CEA in human serum samples with great recoveries (99.4––106 %) demonstrated its capability for clinical analysis.