and Perspectives Sophie Carenco,†,‡,§,∥,⊥ David Portehault,*,†,‡,§ Ced́ric Boissier̀e,†,‡,§ Nicolas Meźailles, and Cleḿent Sanchez*,†,‡,§ †Chimie de la Matier̀e Condenseé de Paris, UPMC Univ Paris 06, UMR 7574, Colleg̀e de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France ‡Chimie de la Matier̀e Condenseé de Paris, CNRS, UMR 77574, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Chimie de la Matier̀e Condenseé de Paris, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Laboratory Heteroelements and Coordination, Chemistry Department, Ecole Polytechnique, CNRS-UMR 7653, Palaiseau, France

Nanoscaled metal borides and phosphides: recent developments and perspectives

Novel development of nanoparticles to bimetallic nanoparticles and their composites: A review

As an alluring metal-free polymeric semiconductor material, graphite-like carbon nitride (g-C3N4; abbreviated as GCN) has triggered a new impetus in the field of photocatalysis, mainly favoured from its fascinating physicochemical and photoelectronic structural features. However, certain inherent drawbacks, involving rapid reassembly of photocarriers, low specific surface area and insufficient optical absorption, limit the wide-range applicability of GCN. Generation of 0D point defects mainly by introducing vacancies (C and/or N) into the framework of GCN has spurred extensive consideration owing to their distinctive qualities to manoeuvre substantially, the optical absorption, radiative carrier isolation, and surface photoreactions. The present review endeavours to summarise a comprehensive study on vacancy defect engineered GCN. Starting from the basic introduction of defects and C/N vacancy modulated GCN, numerous advanced strategies for the controlled designing of vacancy rich GCN have been explored and discussed. Afterwards, light was thrown on the various substantial technologies which are useful for characterising and identifying the introduction of defects in GCN. The salient significance of defect engineering in GCN has been reviewed concerning its impact on optical absorption, charge isolation and surface photoreaction ability. Typically, the achievement of defect engineered GCN has been scrutinised toward various applications like photocatalytic water splitting, CO2 conversion, N2 fixation, pollutant degradation, and H2O2 production. Finally, the review ends with conclusions and vouchsafing future challenges and opportunities on the intriguing and emerging area of vacancy defect engineered GCN photocatalysts.

C-, N-Vacancy defect engineered polymeric carbon nitride towards photocatalysis: viewpoints and challenges

Currently, world is dealing with two major hurdles towards a prosperous economy, i.e., energy crisis and environmental pollution, which challenge the development and growth of the living society. In this regard, semiconductor-oriented heterogeneous photocatalysis, electrocatalysis, and photoelectrocatalysis via fuel cell technology are green and sustainable technologies that have been receiving wide attention by the scientific community for tackling these two issues. In addition, in the present scenario, the synthesis of cost-effective and robust catalysts with high stability, corrosion resistance in any medium, and size and morphology oriented in the micro and nanoscale is a hot topic of research. Therefore, transition metal phosphides (TMPs) and their composite-based catalysts are extensively used in these fields, replacing previously used noble metals such as Pt, Au, and Ag due to scarcity, instability, and high price. Predominantly, nickel phosphide-based materials among all TMPs have proven to be excellent catalysts regarding these fields of application. The metal–phosphorus bonding, basically the Ni–P bonding present in the catalyst, and its resemblance with the [NiFe] hydrogenase makes it more stable and resistive. Several phases of nickel phosphides are available with different lattice structures. Moreover, according to their metal and phosphorus proportion, they can be divided in two categories as metal-rich nickel phosphides and phosphorus-rich nickel phosphides. With respect to this, their activities are also reflected by their elemental contents; the phosphorus-rich nickel phosphides are excellent in electrocatalytic hydrogen evolution reactions (HER), whereas metal-rich nickel phosphides are excellent in electrocatalytic oxygen evolution (OER). However, some metal-rich nickel phosphides with high P/Ni ratio, i.e., Ni5P4, show better activity towards HER because of the high P content. The Ni2P phase also plays an active role in both HER and OER, though it belongs to the metal-rich phase. This shows good catalytic behavior towards HER due to presence of well-defined exposed facets and proper proportion of Ni and P atoms. Furthermore, different types of composites are still being developed by modifying their morphology and size through different synthetic strategies with the expectation of more enhanced activity. This review gives an overview of the design and development of nanostructured nickel phosphide-based materials and their recent significant trends in electrocatalytic, photoelectrocatalytic, and photocatalytic water splitting reactions. Moreover, we present the state-of-art various nickel phosphide materials in last five years, which highlight challenges and future prospects involving some critical issues in these emerging fields that await further exploration, and opportunities in the present and future research.

Recent advances in phase, size, and morphology-oriented nanostructured nickel phosphide for overall water splitting

A complex ternary BiPO4/TiO2/gC3N4 heterostructure has been obtained from a simple impregnation method having good photoactivities for the degradation of phenol under solar-like irradiation. From the wide structural, surface and electronic characterization, we have stated that the formation of the ternary heterojunction notably affect photoactivity of pristine TiO2. Thus, the best result for the binary system was obtained for 70 wt% TiO2-30 wt% BiPO4 system. The incorporation of gC3N4 leads to a further improvement on the photocatalytic activity when it is specifically done over TiO2. By means of photoluminescence spectroscopy and reactive oxygen species formation test, we propose that the effective charge carrier separation is taking place through a cascade-driven electronic mechanism. Therefore, by choosing the adequate band-engineering tailoring an important improved photoactivity can be achieved.

Cascade charge separation mechanism by ternary heterostructured BiPO4/TiO2/g-C3N4 photocatalyst

The photocatalytic properties of TiO2 modified by chromium are usually found to depend strongly on the preparation method. To clarify this problem, two series of chromium-doped titania with a chromium content of up to 1.56 wt % have been prepared under hydrothermal conditions: the first series (Cr:TiO2) is intended to dope the bulk of TiO2, whereas the second series (Cr/TiO2) is intended to load the surface of TiO2 with Cr. The catalytic properties have been compared in the photocatalytic oxidation of formic acid. Characterization data provides evidence that in the Cr/TiO2 catalysts chromium is located on the surface of TiO2 as amorphous CrOOH clusters. In contrast, in the Cr:TiO2 series, chromium is mostly dissolved in the titania lattice, although a minor part is still present on the surface. Photocatalytic tests show that both series of chromium-doped titania demonstrate visible-light-driven photo-oxidation activity. Surface-doped Cr/TiO2 solids appear to be more efficient photocatalysts than the bulk-doped Cr:TiO2 counterparts.

Photocatalysis with Chromium-Doped TiO2: Bulk and Surface Doping

In Situ XRD, XAS, and Magnetic Susceptibility Study of the Reduction of Ammonium Nickel Phosphate NiNH

In the framework of a two stage process for the hydrotreatment of gas oil, the use of noble metal catalysts in the second stage, where the H 2 S partial pressure is considerably decreased, was proposed. Thus, the catalytic properties of a series of Pt x Pd 100− x ( x corresponding to at.% in the alloy) particles supported on zirconia were investigated in tetralin hydrogenation and decahydroquinoline hydrodenitrogenation. TEM micrographs and EDS analysis evidenced the high dispersion of the monometallic and bimetallic composition of the nanoparticles. Whereas a promoting effect is observed in the case of hydrogenation reaction, the introduction of Pd suppressed the catalytic activity in C–N bond scission reaction. This poisoning effect can be simply understood as a linear effect of the segregation of Pd at the surface of PdPt particles. The effect of H 2 S partial pressure on the HDN activity was investigated and showed that for this reaction thioresistance is not improved by alloying.

Bimetallic PtPd on zirconia catalysts for hydrotreating purposes

Nanodispersed MoS2 and CoMoS2 materials containing metastable 1T MoS2 phase have been prepared by solvothermal technique, characterized with several physico-chemical methods and evaluated in the electrocatalytic hydrogen evolution (HER), thiophene hydrodesulfurization (HDS) and 1-pentene hydrogenation (HYD) reactions. The role of different factors in the stabilization of 1T MoS2 phase has been studied. Stability of 1T polymorph upon heating was followed by XPS and Raman spectroscopies and evolution of HER activity. The results of characterizations (Raman, XPS, TEM, XRD) converge to the conclusion that ethylene glycol intercalated between the MoS2 layers stabilizes 1T –MoS2 polymorph. When heated above 200 °C, the solids lose the intercalated ethylene glycol molecules and are transformed to 2 H –MoS2. The presence of cobalt does not influence the stability of 1T phase, but improves both HER and HDS performance due to formation of CoMoS species.

Stability and catalytic properties of 1T-MoS2 obtained via solvothermal synthesis

The invention relates to a composition comprising a mixture of zinc sulphide (ZnS) and molybdenum sulphide (MoS x ) in which the Mo/Zn molar ratio is between 001 and 19 The invention also relates to the process for the preparation thereof and also to the use thereof in photocatalysis and more particularly to the use thereof in photocatalysis for the production of dihydrogen from water (H 2 O) and/or from hydrogen sulphide (H 2 S) and/or any other source of protons in the presence of a source which emits in the ultraviolet and/or visible spectrum

Pavel Afanasiev

Papers

Photocatalysis with Chromium-Doped TiO2: Bulk and Surface Doping

In Situ XRD, XAS, and Magnetic Susceptibility Study of the Reduction of Ammonium Nickel Phosphate NiNH

Bimetallic PtPd on zirconia catalysts for hydrotreating purposes

Stability and catalytic properties of 1T-MoS2 obtained via solvothermal synthesis

Metal sulphide-based composite photocatalyst for producing hydrogen