Clement Maheu

Institut des Materiaux Jean Rouxel | CNRS

An ideal proton exchange membrane should only permeate protons and be leak tight for fuels. Graphene is impermeable to water and poorly conducting to protons. Here, we chemically functionalized monolayer graphene to install sulfophenylated sp3 dislocations by diazotization. Selective to protons, transmembrane areal conductances are up to ~50 S/cm2,...

Interfaces are crucial elements that define the electronic properties of perovskite solar cells (PSCs). However, obtaining the band structure of a full PSC and accessing its buried layers and interfaces without modifying the device is challenging. A tapered cross section (TCS) of a PSC ( i.e. , a PSC polished under a very shallow angle) offers acce...

In the field of perovskite solar cells, explorations of new lead-free all-inorganic perovskite materials are of great interest to address the instability and toxicity issues of lead-based hybrid perovskites. Recently, copper-antimony-based double perovskite materials have been reported with ideal band gaps, which possess great potential as absorber...

The understanding of interfacial charge transfer processes is vital to the design of efficient photoanodes in photoelectrochemical (PEC) water splitting. Bismuth vanadate (BiVO 4 ) is a promising photoanode material to drive...

Interfaces are key elements that define electronic properties of the final device. Inevitably, most of the active interfaces of III–V semiconductor devices are buried and it is therefore not straightforward to characterize them. The Tapered Cross Section Photoelectron Spectroscopy (TCS‐PES) approach is promising to address such a challenge. That th...

Carbon supported metallic nanomaterials are of great interest due to their low‐cost, high durability and promising functional performance. Herein, a highly active oxygen evolution reaction (OER) electrocatalyst comprised of defective carbon shell encapsulated metal (Fe, Co, Ni) nanoparticles and their alloys supported on in‐situ formed N‐doped grap...

Lattice matched n-type AlInP(100) charge selective contacts are commonly grown on n-p GaInP(100) top absorbers in high-efficiency III-V multijunction solar or photoelectrochemical cells. The cell performance can be greatly limited by the electron selectivity and valance band offset at this heterointerface. Understanding of the atomic and electronic...

Interfaces are key elements that define electronic properties of the final device. Inevitably, most of the active interfaces of III-V semiconductor devices are buried and it is therefore not straightforward to characterize them. The Tapered Cross-Section Photoelectron Spectroscopy (TCS-PES) approach is promising to address such a challenge. We demo...

Lattice matched n-type AlInP(100) charge selective contacts are commonly grown on n-p GaInP(100) top absorbers in high-efficiency III-V multijunction solar or photoelectrochemical cells. The cell performance can be greatly limited by the electron selectivity and valance band offset at this heterointerface. Understanding of the atomic and electronic...

A strong short circuit current density (JSC) loss is observed when using phenetylammonium iodide (PEAI) as n‐side passivation in p‐i‐n perovskite solar cells. Comparing experiments with drift diffusion simulations, different hypotheses for the origin of the JSC loss are being presented and evaluated. Whereas the optical properties of the investigat...

An accurate experimental determination of electronic structure in semi-conductors nanopowders is a challenging task. We propose here to combine UPS and UV-Vis spectroscopies in order to get the full description of electronic bands alignment of powder samples, TiO2 rutile and anatase. For UPS measurements, two preparation methods, namely dropping me...

Since their introduction in 2017, the efficiency of lead-free halide perovskite solar cells based on Cs2AgBiBr6 has not exceeded 3%. The limiting bottlenecks are attributed to a low electron diffusion length, self-trapping events and poor selectivity of the contacts, leading to large non-radiative VOC losses. Here, 2D/3D hybrid double perovskites a...

Les sulfures de métaux de transition ont été utilisés comme co-catalyseurs de TiO2 pour la production photocatalytique de H2, permettant ainsi d’établir des liens entre les propriétés intrinsèques variées de ces sulfures de métaux de transition et l’activité du photocatalyseur résultant. La capacité des sulfures de métaux de transition à activer H2...

The presence of defects and chemical dopants in metal-free carbon materials plays an important role in the electrocatalysis of the oxygen reduction reaction (ORR). The precise control and design of defects and dopants in carbon electrodes will allow the fundamental understanding of activity-structure correlations for tailoring catalytic performance...

Metal halide perovskites are the first solution processed semiconductors that can compete in their functionality with conventional semiconductors, such as silicon. Over the past several years, perovskite semiconductors have reported breakthroughs in various optoelectronic devices, such as solar cells, photodetectors, light emitting and memory devic...

The presence of defects and chemical dopants in metal-free carbon materials plays important roles in the electrocatalysis of the oxygen reduction reaction (ORR). The precise control and design of defects and dopants in carbon electrodes will allow the fundamental understanding of activity-structure correlations for tailoring catalytic performance o...

The surface, interface, and bulk properties are a few of the most critical factors that influence the performance of perovskite solar cells. The photoelectron spectroscopy (PES) is used as a technique to analyses these properties. However, the information depth of PES is limited to 10-20 nm, which makes it not suitable to study the complete devices...

Many parameters influence the photocatalytic production of H2. Identifying and quantifying them is necessary for correct comparison of photocatalysts and right understanding of involved mechanism. In this work, we studied the photocatalytic dehydrogenation of isopropanol with titania-supported ruthenium disulfide. We studied the influence of seven...

Photocatalysis is a promising way to synthesize H2 as a solar fuel. On one hand, the photocatalytic H2 production stores solar energy under chemical energy. On the other hand, it produces H2 with a renewable process using water and bio-based alcohols as a feedstock. This Ph.D thesis aims to study the photocatalytic dehydrogenation of alcohols with...

The electronic structure of a semiconductor rules its optoelectronic properties. In photocatalysis, the size of the band gap determines the photons that can be absorbed/ The position of the valence band maximum (EVB) and of the conduction band maximum (ECB) fix the potential of the photogenerated holes and electrons, respectively. But each powder...

Among the inorganic compounds, many oxides and sulfides are known to be semiconductors. At the crossroads of these two families, oxysulfide MxOySz compounds were much less investigated because they are scarce in nature and complex to synthesize. Amongst them, lanthanide oxysulfide Ln2O2S (Ln = lanthanide) are indirect bandgap semiconductors, with w...

Pt/TiO2 photocatalysts were prepared by incipient wetness impregnation followed by oxidative and/or reductive thermal treatments. By varying the TiO2 form (commercial P25 and P90, and homemade shape-controlled), the Pt loading (0.2-1 wt% Pt) and the treatment temperature (200-600 °C), it has been possible to tune the Pt cluster size. An increase in...

Transition metal sulfides Photocatalysts Titanium oxide a b s t r a c t A series of transition metals sulfides deposited on anatase titania (MS x /TiO 2) were prepared by precipitation of transition metals salts with thioacetamide in aqueous medium under reflux. The solids were characterized by XRD, XPS, temperature programmed reduction and transmi...

Hydrogen (H2) production from photocatalytic alcohol dehydrogenation is a promising solution to tackle energy issues. Many factors are involved in photocatalytic process making it hard to design efficient, cheap and stable photocatalysts. It is complex to identify which factors are decisive and how they influence the overall activity. We establishe...

An accurate experimental determination of electronic structure in semi-conductors nanopowders is a challenging task. We propose here to combine UPS and UV-Vis spectroscopies in order to get the full description of electronic bands alignment of powder samples, TiO2 rutile and anatase. For UPS measurements, two preparation methods, namely dropping me...

Nine transition metal sulfides deposited on titanium dioxide were tested for the photocatalytic dehydrogenation of isopropanol. Activities were compared based on photon yields and on the apparent activation energy for dihydrogen production. A structure-activity relationship of the bifunctional catalysts is discussed. Capacity to activate hydrogen,...

Dihydrogen (H2) production through photocatalytic dehydrogenation of alcohol from biomass is one solution to produce clean and renewable energy. Titanium dioxide (TiO2) is the most used photocatalyst. Deposition of semiconductor or metal co-catalysts on its surface enhances its efficiency. At the interface, a band alignment occurs and strongly inf...

To address global warming, researches on the development of clean and renewable energy play a key role. Production of hydrogen by photocatalytic water splitting is one possibility. Titanium dioxide (TiO2) is highly studied for its photocatalytic properties on hydrogen evolution reaction (HER). However, alone its efficiency is not enough for catalyt...

A reusable zirconium-based catalyst for the cycloaddition of CO2 to propylene oxide (PO) was prepared by the surface organometallic chemistry (SOMC) methodology. Accordingly, well-defined amounts of the ZrCl4·(OEt2)2 precursor were grafted on the surface of silica dehydroxylated at 700 °C (SiO2-700) and at 200 °C (SiO2-200) in order to afford surfa...