Hubert H Girault

• PhD
• Professor (Full) at Swiss Federal Institute of Technology in Lausanne

The present work reports a simple approach to manufacture electrocatalytically active gas diffusion electrodes (GDEs) in two steps i) inkjet printing and ii) flash light irradiation from a Xenon flash...

This article aims to present the redox aspects of lithium-ion batteries both from a thermodynamic and from a conductivity viewpoint. We first recall the basic definitions of the electrochemical potential of the electron, and of the Fermi level for a redox couple in solutions. The Fermi level of redox solids such as metal oxide particles is then dis...

Optical second-harmonic generation (SHG) is achieved using adsorbed gold nanoparticles (AuNPs) with an average diameter of 16 nm at the aqueous solution–air interface in reflection. A detailed analysis of the depth profile of the SHG intensity detected shows that two contributions appear in the overall signal, one arising from the aqueous solution–...

A few seconds flash photopyrolysis is used as efficient screening tool for the investigation of selected biomass in producing syngas, hydrogen and biochar. This innovative approach allowed rapid pyrolysis of the biomass, which was followed by a precise gas analysis and quantification, using Mass Spectrometry (MS). The analysis of the gas compositio...

In the human body, there are millions of living microorganisms involved in protecting the body from invaders, helping digestion and regulating moods, but there are also harmful pathogens that cause infectious diseases. For instance, the coronavirus (COVID-19) has caused considerable loss of life since its outbreak. Comprehensive analysis and charac...

This paper evaluated the use of soft-probe scanning electrochemical microscopy complementarily with confocal laser scanning microscopy to study the effects of different antimicrobial agents and treatments on E. coli DH5α biofilm. The antimicrobial agents were sodium azide, silver nanoparticles, and a flashlight. The effects of these agents were mon...

Biofilm‐associated infections, which are able to resist antibiotics, pose a significant challenge in clinical treatments. Such infections have been linked to various medical conditions, including chronic wounds and implant‐associated infections, making them a major public‐health concern. Early‐detection of biofilm formation offers significant advan...

Biofilm‐associated infections, which are able to resist antibiotics, pose a significant challenge in clinical treatments. Such infections have been linked to various medical conditions, including chronic wounds and implant‐associated infections, making them a major public‐health concern. Early‐detection of biofilm formation offers significant advan...

This paper evaluated the use of Soft-Probe-SECM to study the effects of different antimicrobial agents and treatments on E. coli biofilms. The antimicrobial agents were sodium azide, silver nanoparticles, and a flashlight. The effects of these agents were monitored by measuring the change in biofilm properties, such as biofilm thickness, viability,...

Voltammetric sandwich assays were constructed by integrating capture bioreceptors-conjugated magnetic nanocomposites, namely Fe3O4/MIL-101(Fe)-(NH)(CO)-COOH (FO/MOF) and alkaline phosphatase (ALP)-labeled detection antibodies on an eight-well screen-printed carbon ink electrode (SPCIE) for the simultaneous detection of liver cancer biomarkers, huma...

Macromolecular mass fingerprinting using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry is a quick tool for biochemical analysis. In combination with algorithms for automated data analysis and interpretation, it has wide application potentials in life science, especially for diagnostic purposes. This review aims to ill...

Waste tires are a major environmental concern due to their non-degradable nature and the large area occupied in landfills worldwide. Several recycling processes have been applied to minimize the high...

In 2006, the concept of redox targeting was introduced in which solubilized redox‐active molecules are used to mediate reversible electron transfer reactions. The aim was to address conductivity concerns rising from insulating lithium‐insertion material (e.g. LiFePO 4 particles) by using freely diffusing molecules as relays between the current coll...

Scanning electrochemical microscopy (SECM) is one of the scanning probe techniques that has attracted considerable attention because of its ability to interrogate surface morphology or electrochemical reactivity. However, the quality of SECM images generally depends on the sizes of the electrodes and many uncontrollable factors. Furthermore, manipu...

Scanning electrochemical microscopy (SECM) is one of the scanning probe techniques that has attracted considerable attention because of its ability to interrogate surface morphology or electrochemical reactivity. However, the quality of SECM images generally depends on the sizes of the electrodes and many uncontrollable factors. Furthermore, manipu...

The visible light driven water oxidation reaction (WOR) by the organic electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (TCNQF4) was studied at the water|butyronitrile interface. The WOR was performed at neutral pH, and without any metal or organometallic catalysts. The oxygen generated was measured by GC-MS and cyclic voltam...

A microwater|butyronitrile (W|BCN) interface was used to study the effect of the interfacial chemical polarization on the efficiency of the visible-light induced water oxidation reaction (WOR) by the electron acceptor/photosensitizer TTF/TTF•+self-assembled on the surface of Co3O4 microparticles, acting as redox electrocatalysts. The polarized W|BC...

Wound biofilms represent a particularly challenging problem in modern medicine. They are increasingly antibiotic resistant and can prevent the healing of chronic wounds. However, current treatment and diagnostic options are hampered by the complexity of the biofilm environment. In this review, we present new chemical avenues in biofilm sensors and...

Biomass splitting into gases and solids using flash light irradiation is introduced as an efficient photo-thermal process to photo-pyrolyze dried natural biomass powders to valuable syngas and conductive porous carbon (biochar). The photo-thermal reactions are carried out in a few milliseconds (14.5 ms) by using a high-power Xenon flash lamp. Here,...

Wound biofilms represent a particularly challenging problem in modern medicine. They are increasingly antibiotic resistant and can prevent the healing of chronic wounds. However, current treatment and diagnostic options are hampered by the complexity of the biofilm environment. In this review, we present new chemical avenues in biofilm sensors and...

Here, the semi-invasive direct electrochemical detection of melanoma biomarkers in non-treated skin has been envisaged. The enzyme tyrosinase (TYR) was to be addressed with a microneedle electrochemical sensor. The microneedles were fabricated by polydimethylsiloxane (PDMS) casting with stable polymers. The as-prepared microneedles (MNs) were then...

Sustainable water oxidation requires low-cost, stable, and efficient redox couples, photosensitizers, and catalysts. Here, we introduce the in situ self-assembly of metal-atom-free organic-based semiconductive structures on the surface of carbon supports. The resulting TTF/TTF•+@carbon junction (TTF = tetrathiafulvalene) acts as an all-in-one highl...

A multiplexed electrochemical platform has been designed for electrochemical screening applications such as bacteria detection. It includes 16 x 16 electrochemical cell array in a 2‐electrode mode fabricated by a combination of screen printing, inkjet printing and flash light sintering techniques wherein each cell is addressed sequentially by a por...

A redox dual-flow battery is distinct from a traditional redox flow battery (RFB) in that the former includes a secondary energy platform, in which the pre-charged electrolytes can be discharged in external catalytic reactors through decoupled redox-mediated hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The concept offers s...

The role of the discreteness of the charges at ITIES has recently been revisited within the framework of the so-called "Discrete Helmholtz" model. The main conclusion of this model is that the potential drop across an ITIES takes place over a bilayer of correlated ions rather than across two back-to-back diffuse layers as suggested by the Gouy Chap...

Redox flow battery (RFB) has drawn considerable attention past years for large-scale energy storage applications. However, RFB’s suffer from low energy density and premature degradation failures were reported due to uncontrolled electrolyte imbalance, limiting their commercialization. To address those concerns, we proposed in 2014 an innovative con...

H2O2 is a versatile chemical and can be generated by the oxygen reduction reaction (ORR) in proton donor solution in molecular solvents or room temperature ionic liquids (IL). We investigated this reaction at interfaces formed by eleven hydrophobic ILs and acidic aqueous solution as a proton source with decamethylferrocene (DMFc) as an electron don...

After discussing the fundamental issue of charge distributions at polarized interfaces, we present the concept of the “Discrete Helmholtz Model” for liquid-liquid interfaces and also for other non-metallic interfaces. We introduce the newly discovered ionosomes, which are nano liquid-liquid interfaces. We finish by presenting our work of water spli...

Proton-exchange membrane fuel cell (PEMFC), designed mainly for mobility applications, converts chemical energy to electrical energy. The formation of electrodes for PEMFC is a delicate balance of transport media. The diffusion of gas, electrons, and protons, known as a triple phase boundary (TPB), plays a key role in the fuel cell operation and pe...

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Skin problems are often overlooked due to a lack of robust and patient-friendly monitoring tools. Herein, we report a rapid, noninvasive, and high-throughput analytical chemical methodology, aiming at real-time monitoring of skin conditions and early detection of skin disorders. Within this methodology, adhesive sampling and laser desorption ioniza...

An amperometric sensor based on an inkjet-printed graphene electrode (IPGE) modified with amine-functionalized montmorillonite (Mt-NH2) for the electroanalysis and quantification of gentisic acid (GA) has been developed. The organoclay used as IPGE modifier was prepared and characterized by infrared spectroscopy, X-ray diffraction, scanning electro...

Investigating and understanding dynamic biofilm growth mechanisms is challenging, often because state-of-the-art optical characterization tools provide limited information. Micrometric electrochemical imaging of Escherichia coli biofilms using Soft-Probe-Scanning Electrochemical Microscopy (Soft-Probe-SECM) is herein presented as a complementary te...

H2 may be evolved biphasically using a polarised liquid|liquid interface, acting as a “proton pump”, in combination with organic soluble metallocenes as electron donors. Sustainable H2 production requires methodologies to recycle the oxidised donor. Herein, the photo‐recycling of decamethylferrocenium cations (DcMFc⁺) using aqueous core‐shell semic...

Scanning electrochemical microscopy (SECM) offers a highly sensitive and convenient approach for electrochemical mapping of interleukin-6 (IL-6), an oral cancer protein biomarker. In this study, we utilized the SECM to map the distribution of IL-6 for imaging different cancer stages on the tissue sections. The SECM results indicated that IL-6 was e...

The mechanism by which interfaces in solution can be polarised depends on the nature of the charge carriers. In the case of a conductor, the charge carriers are electrons and the polarisation is homogeneous in the plane of the electrode. In the case of an insulator covered by ionic moieties, the polarisation is inhomogeneous and discrete in the pla...

The structure of the polarised interface between two immiscible electrolyte solutions (ITIES) has usually been deduced from electrocapillarity and capacitance measurements. However, these two methods only offer an indirect access to the surface change density, by differentiation and integration. In this work, we analyse the dependence on the potent...

The synthesis of noble metal nanoparticles (i.e., silver and gold) for electrochemical applications has been widely studied using mainly wet synthesis chemical methods or electrochemical deposition methods. In this work, we propose a single-step flash photochemical method for synthesizing noble metal nanoparticles (i.e., silver, gold, and Au:Ag) in...

Producing hydrogen from water using a redox mediator on solid electrocatalyst particles in a reactor offers several advantages over classical electrolysis in terms of safety, membrane degradation, purity and flexibility. Herein, vanadium-mediated hydrogen evolution on a commercial and low-cost Mo2C electrocatalyst is studied through the development...

Oral cancer poses a serious threat worldwide owing to its soaring case-fatality rate and its metastatic characteristics of spreading to the other parts of the body. Despite the recent breakthroughs in biomedical sciences, the detection of oral cancer at an early stage is still challenging. Conventional diagnosis in clinics and optical techniques to...

Low-grade heat (below 200 ℃) is available in vast quantities from industry, or from standard roof-top solar thermal collectors. However, production of electric power from these heat sources is challenging with existing technologies. Thermally regenerative batteries allow both the conversion and the storage of thermal energy into electric power, but...

The MnIII/MnII redox couple with a standard potential of +1.51 V versus the standard hydrogen electrode (SHE) has attracted interest for the design of V/Mn redox flow batteries (RFBs). However, MnIII disproportionation leads to a loss of capacity, an increase in pressure drop, and electrode passivation caused by the formation of MnO2 particles duri...

The distribution of electrolytes in an electric field usually relies on theories based on the Poisson-Boltzmann formalism. This mean-field approach predicts that, in the case of a metallic electrode, ionic charges screen the electrode potential, leading to concentration-dependent ion distributions. This theoretical framework was first applied at so...

Air driven gas boosters are often deployed in small scale compression systems. Manufacturers specifications, reporting outlet flow for a fixed inlet pressure, do not reflect the batch operation from a limited source storage. Thus, the dynamic variation of critical process parameters such as efficiency, temperature and flow are not documented. Using...

Corrosion of carbon-based electrodes and bipolar plates is a major challenge and a common cause of failure in commercial vanadium redox flow batteries (VRFB). Herein, we describe a typical carbon corrosion that occurred on several stacks of a 10kW/40kWh and a 200kW/400kWh commercial vanadium redox flow batteries (VRFB) installed in the framework of...

Manganese, an earth-abundant transition metal, exists as Mn(III)/Mn(II) redox couple at a standard potential of +1.51V vs. SHE. It has drawn interest for implementation as positive side in V/Mn redox flow battery (RFB) due to higher achievable energy density than all-vanadium RFB. Unfortunately, Mn(III) disproportionation into Mn(II) and MnO 2 (s)...

Scanning electrochemical microscopy (SECM) is a scanning probe technique that is composed of a micro- or nanoelectrode that can be scanned in close proximity to an interface. Faradaic current signals can be recorded due to the flux of redox active species between the sample and an amperometric SECM probe. SECM can be used to image the topography an...

Here we report the design of a disposable single-drop voltammetric sensor for the quantitative determination of antipsy-chotic drug trifluoperazine (TFP). The sensor was build using inkjet-printed carbon nanotube (CNT) electrodes which were modified with dimercaptosuccinic acid (DMSA) coated magnetite nanoparticles uniformly dispersed over reduced...

Prussian blue (PB) and Prussian blue analogues (PBAs) are commonly synthesized by conventional methods, such as chemical precipitation, thermal decomposition and electrochemical deposition. Herein, we have successfully synthesized Prussian blue by oxidative Print-Light-Synthesis (PLS) with a cubic Fe4[Fe(CN)6]3 phase, as confirmed by XRD compared t...

This work describes a new sensitive sensor for the simultaneous electrochemical determination by square wave anodic stripping voltammetry of Cd2+ and Pb2+ ions in aqueous solution, based on a disposable ink-jet-printed graphene electrode (IPGE) modified by a thin film of montmorillonite (Mont) clay mineral. The clay was characterized by X-ray diffr...

High-purity standards are required for hydrogen used in fuel cell vehicles. The relative abundance of contaminants is highly influenced by the production pathway. Hydrogen obtained from water electrolysis presents three main pollutants: Nitrogen, Oxygen and Water. Herein, the engineering and implementation of removal techniques in a commercial 50 k...

Inkjet printing of electrochemical sensors using a highly loaded mildly edge‐oxidized graphene nanosheet (EOGN) ink is presented. An ink with 30 mg/mL EOGNs is formulated in a mixture of N‐methyl pyrrolidone and propylene glycol with only 30 min of sonication. The absence of additives, such as polymeric stabilizers or surfactants, circumvents reduc...

Redox flow batteries (RFBs) are among the most investigated technologies for large scale energy storage applications. Since the first commercialization of all-vanadium RFB (in the early 90’s), the technology has evolved towards the development of new systems. This review focuses on three innovative concepts including aqueous organic RFB (AO-RFB), d...

Continuous hydrothermal flow synthesis (CHFS) of Ni-Fe Layered Double Hydroxide (LDH) leads to waterborne dispersions of 2D nanoplatelets in the range of 10-50 nm in lateral size. Conversion of the as-synthesized LDH nanoplatelet dispersion into inkjet printing inks results in high precision patterning and complete substrate coverage with low LDH l...

Charge transfer phenomena at the interface between two immiscible electrolyte solutions (ITIES) are electrochemical reactions taking place in soft media. Owing to their liquid nature, the ITIES shows a large panel of electrochemical reactions including electron transfer reactions, ion transfer reactions, coupled electron–ion transfer reactions or b...

Sodium chromium hexacyanoferrate (NaCrHCF) is here obtained using a facile co-precipitation method at room temperature. The powder was investigated in terms of potential use as a cathode material for aqueous...

The “dual-circuit redox flow battery” takes advantage of a conventional all-vanadium redox flow battery (VRFB) combined with a separated catalytic hydrogen evolution reactor. Depending on demand, the VRFB can be conventionally discharged or supply H2 by using the catalytic reactor. However, during hydrogen generation, protons are consumed and a sta...

Transition metal incorporated into molybdenum sulfide and tungsten sulfide matrixes are promising candidates for hydrogen evolution due to the unique chemical and physical properties. Here, we first describe a general strategy for the synthesis of rod‐like ternary refractory metal sulfides (MWS x ; M= Ni, Co, Fe and Mn) through a simple hot‐injecti...

The search for highly active, consisted of earth abundant elements and non-expensive catalysts for hydrogen evolution reaction are vital and demanding tasks to minimize energy consumption. Transition metal incorporated into molybdenum sulfides are promising candidates for hydrogen evolution due to the unique chemical and physical properties. Here,...

Detailed studies on hydrogen evolution by decamethylruthenocene ([Cp*2RuII]) highlighted that metallocenes are capable of photoreducing hydrogen without the need for an additional sensitizer. Electrochemical, gas chromatographic, and spectroscopic (UV/Vis, ¹H and ¹³C NMR) measurements corroborated by DFT calculations indicated that the production o...

A non-invasive electrochemical melanoma detection approach based on using adhesive tapes for collecting and fixing cells from a suspicious skin area and transferring the cells into a scanning electrochemical microscope (SECM) is presented. The adhesive layer collects the cells reproducibly and keeps them fixed on the tape in an electrolyte solution...

By hyphenating inkjet printing and flash light irradiation, Ni- and NiFe-nano-electrocatalysts of diameters below 2.5 nm with ultralow loadings below 2 µg·cm–2 are synthesized. To achieve this, nanoliter ink volumes containing Ni and Fe chlorides as catalyst precursors are rapidly printed on large-scale carbon nanotube-coated glassy carbon electrod...

An electrochemical sensor is described for the determination of L-dopa (levodopa; 3,4-dihydroxyphenylalanine). An inkjet-printed carbon nanotube (IJPCNT) electrode was modified with manganese dioxide microspheres by drop-casting. They coating was characterized by field emission scanning electron microscopy, Fourier-transform infrared spectroscopy a...

All redox flow batteries suffer from low energy storage density in comparison with conventional Li-ion batteries. However, this issue can be mitigated by utilization of solid energy storage materials to enhance the energy storage capacity. In this paper we demonstrate the utilization of copper hexacyanoferrate (CuHCF) Prussian blue analogue for thi...

Diffusion controlled chemical reactions are usually observed in three dimensional media. In contrast, planar bimolecular reactions taking place between reagents adsorbed at a soft interface are two-dimensional and therefore cannot be studied within the same formalism. Indeed, soft interfaces allow the adsorbed species to freely diffuse in a liquid-...

Polyacrylamide-coated, carbon nanotube (PA/CNT) electrodes were prepared by an ink-jet printing process and used to measure pyocyanin and uric acid in a wound fluid simulant at 37 oC. These two molecules are potential indicators of infection and therefore their detection could prove useful for monitoring wound healing. Pyocyanin is a marker for the...

A new approach for large-scale fabrication of miniaturized, reliable and planar solid-state reference electrodes on flexible substrates is presented. Inkjet printing technique was used for the fabrication of conductive path and silver patterns that were chemically transformed into the Ag/AgCl electrodes and drop-casted with a membrane containing a...

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry is used to detect intact whole exosomes, yielding exosomal fingerprints within minutes. This rapid exosome detection approach is proposed as a potential tool for cancer studies. Melanoma, a dangerous form of skin cancer, is investigated as a cancer model. The approach allo...

Multi-stall fast charging stations are often thought to require megawatt-range grid connections. The power consumption profile of such stations results in high cost penalties due to monthly power peaks and expensive linkage fees. A local energy storage system (ESS) can be used to address peak power demands. However, no appropriate sizing method is...

A disposable acetaminophen biosensor based on inkjet‐printed CNT electrodes (IJPCNT) modified with amidase/cerium dioxide@graphene nanoribbons composite was developed (ACeO2@GNR/IJPCNT). The enzyme amidase A was used for the first time as a recognition element. Inkjet‐printed CNT electrodes served as a basis for the construction of a biosensor that...

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry is used to detect intact whole exosomes, yielding exosomal fingerprints within minutes. This rapid exosome detection approach is proposed as a potential tool for cancer studies. Melanoma, a dangerous form of skin cancer, is investigated as a cancer model. The approach allo...

Water electrolysis is a promising approach to hydrogen production from renewable energy sources. Alkaline water electrolyzers allow using non-noble and low-cost materials. An analysis of common assumptions and experimental conditions (low concentrations, low temperature, low current densities, and short-term experiments) found in the literature is...

This work investigates the effect of current density on the hydrogen gas bubble formation during electrolysis on a platinum electrode. Local detection of bubble evo- lution was performed electrochemically by using an hydrogen collecting microelectrode placed in close proximity of a larger hydrogen generating platinum electrode. The mi- croelectrode...

We report the in-situ self-assembly of TTF, TTF•+ and BF4– or PF6– into p-type semiconductors on the surface of Pt microparticles dispersed in water/acetonitrile mixtures. The visible light photoactivation of these self-assemblies leads to water oxidation forming O2 and H⁺, with an efficiency of 100 % with respect to the initial concentration of TT...

Corrosion of carbon‐based electrodes and bipolar plates is a major hurdle and can be a cause of failure in commercial vanadium redox flow batteries (VRFBs). Carbon corrosion was found to occur in a commercial VRFB (10 kW/40 kWh), whereby cracks through bipolar plates enabled the electrolyte to leach the copper current collectors at the end of the s...

Butyronitrile is an organic solvent stable enough to be used in photochemical reactions at liquid/liquid interfaces. However, it provides a rather short polarisation window making the analysis of ion transfer across the water|butyronitrile interface challenging. Here, steady-state cyclic voltammetry, at microhole-supported micro-interfaces, was use...

Inkjet‐Printed Mesoporous TiO2 and Perovskite Layers for High Efficiency Perovskite Solar Cells: Inkjet‐Printing of “open‐pore” TiO2 thin films and Cs0.10Gua0.05FA0.83MA0.17PbI2.63Br0.37 perovskite is studied, with optimized inkjet‐printed TiO2 film structures eventually yielding higher efficiencies when incorporated in photovoltaic devices than sp...

Perovskite solar cells with mesoporous TiO2 electron transport layers have previously reached >22 % efficiency at the laboratory scale (<1 cm²), however, these layers are fabricated using spin‐coating, which is not conducive to large‐scale or high throughput fabrication. This report describes the inkjet printing of open‐pore mesoporous TiO2 thin fi...

The incessant growth in energy demand has resulted in the deployment of renewable energy generators to reduce the impact of fossil fuel dependence. However, these generators often suffer from intermittency and require energy storage when there is over-generation and the subsequent release of this stored energy at high demand. One such energy storag...

Inks for the inkjet-deposition of Titanium dioxide and hybrid organic inorganic perovskites were synthesized and then used to deposit films for high efficiency perovskite solar cell devices. The inkjet-printed titanium dioxide electron transport layer was optimized in reference to state-of-the-art spin-coated tio2 films. After observing that the pr...

A combination of immuno‐affinity enrichment strategy and sensitive amperometric read‐out was implemented in a point‐of‐care platform, intended for bacterial infection analysis. Bacterial cells, selectively captured and enriched from complex matrices via immuno‐affinity, were detected by amperometric monitoring the redox state of metabolic activity...

A combination of immuno‐affinity enrichment strategy and sensitive amperometric read‐out was implemented in a point‐of‐care platform, intended for bacterial infection analysis. Bacterial cells, selectively captured and enriched from complex matrices via immuno‐affinity, were detected by amperometric monitoring the redox state of metabolic activity...