Modelled kinetics of the rate of hydrogen evolution as a function of metal catalyst loading in the photocatalysed reforming of methanol by Pt (or Pd)/TiO2

Mechanistic Study of Glucose Photoreforming over TiO2-Based Catalysts for H2 Production

Glucose is a key intermediate in cellulose photoreforming for H₂ production. This work presents a mechanistic investigation of glucose photoreforming over TiO₂ and Pt/m-TiO₂ catalysts. Analysis of the intermediates formed in the process confirmed the α-scission mechanism of glucose oxidation forming arabinose (C_n-1 sugar) and formic acid in the initial oxidation step. The selectivity to sugar products and formic acid differed over Pt/TiO₂ and TiO₂, with Pt/TiO₂ showing the lower selectivity to formic acid due to enhanced adsorption/conversion of formic acid over Pt/TiO₂. In situ ATR-IR spectroscopy of glucose photoreforming showed the presence of molecular formic acid and formate on the surface of both catalysts at low glucose conversions, suggesting that formic acid oxidation could dominate surface reactions in glucose photoreforming. Further in situ ATR-IR of formic acid photoreforming showed Pt-TiO₂ interfacial sites to be key for formic acid oxidation as TiO₂ was unable to convert adsorbed formic acid/formate. Isotopic studies of the photoreforming of formic acid in D₂O (with different concentrations) showed that the source of the protons (to form H₂ at Pt sites) was determined by the relative surface coverage of adsorbed water and formic acid.

Microbial Resistance to Carbapenems in Effluents from Gynaecological, Paediatric and Surgical Hospital Units

The aim of this work is to identify and count antimicrobial resistance (AMR) in hospital effluents (HEs) of 2 units of the University Hospital Mohamed VI the Mother and Child Hospital (MCH) and the Ar-razi Surgical Hospital (ArzH), and to compare the two hospital units in terms of ARMs and seasonal variation. Each HE was sampled during 2016 and 2017. After identification of the pathogenic strains and determination of AMR, the results were reported for 24 ABs, including 3 carbapenems (CBP), and their consumption rates. The Predicted environmental concentration (PEC) rate of carbapenems in the HE of the study sites is calculated. A comparative analysis of the AMR of the isolated bacterial species was performed and related to the evolution of PEC in HEs. In the ArzH effluents:15 strains isolated, 7 are carbanepenem-resistant Enterobacteria (CRE) and are resistant to at least one of the 3 carbapenems tested. ArzH and MCH effluents respectively show some similarities: 26.87% and 28.57% of isolated bacteria are resistant to ertapenem while 43.48% and 57.14% are resistant to meropenem. However, for imipenem, the MCH effluent has a higher percentage of bacterial antibiotic resistance than ArzH. In addition, the percentage of resistance in each hospital unit effluent is mainly in relation with the increasing antibiotic consumption and predicted environmental values PEC for very antibiotic in each unit in the same period.

The Role of Metal Nanoparticles in Promoting Photocatalysis by TiO2

In this review, we highlight the role played by metal nanoparticles (NPs) in photocatalytic oxidation with titania as a support. This is presented in two parts, namely, partial photo-oxidation in which an organic sacrificial agent is oxidised in anaerobic conditions to produce hydrogen (photo-reforming), and photo-oxidative mineralisation of organics in aerobic conditions. We present some rules for such reactions that dictate which organic molecules can react readily, and which metals are likely to be useful for such reactions. Generally, the presence of metal NPs enhances enormously the ability of titania to yield hydrogen from photo-reforming, and a wide range of molecules can be used, including biomass. The metal NPs most used are those that are easily reduced, that is, the precious metals. The large enhancement in rate seen with metal for hydrogen production is not so extreme for the oxidation reactions, but is still significant. An important factor in all of this catalysis is the nature of the interaction between the metal NPs, which can play a multiplicity of chemical and electronic roles, and the photoactive support. A sharp dependency of rate on loading of metal is found, with maximum rates at ~0.5–2 wt% loading, depending on the metal used. The source of this dependency is the bifunctional nature of the system, in which the intimacy of both materials is crucial to performance. This rate variation is linked to the interface between the two, which is then linked to the size of the metal NPs. In fact, the rate is proportional to an area adjacent to the metal particles that we call the expanding photocatalytic area and overlap (EPAO) kinetic model. This model describes the dependence well. Rising rates with increasing coverage of particles is associated with increase in this total area but, at the maximum, these areas overlap and at higher loadings the available active area diminishes, reproducing the observed behaviour well.

Dual promotional effect of CuxO clusters grown with atomic layer deposition on TiO2 for photocatalytic hydrogen production

The promotional effects on photocatalytic hydrogen production of Cu_xO clusters deposited using atomic layer deposition (ALD) on P25 TiO₂ are presented. The structural and surface chemistry study of Cu_xO/TiO₂ samples, along with first principles density functional theory simulations, reveal the strong interaction of ALD deposited Cu_xO with TiO₂, leading to the stabilization of Cu_xO clusters on the surface; it also demonstrated substantial reduction of Ti⁴⁺ to Ti³⁺ on the surface of Cu_xO/TiO₂ samples after Cu_xO ALD. The Cu_xO/TiO₂ photocatalysts showed remarkable improvement in hydrogen productivity, with 11 times greater hydrogen production for the optimum sample compared to unmodified P25. With the combination of the hydrogen production data and characterization of Cu_xO/TiO₂ photocatalysts, we inferred that ALD deposited Cu_xO clusters have a dual promotional effect: increased charge carrier separation and improved light absorption, consistent with known copper promoted TiO₂ photocatalysts and generation of a substantial amount of surface Ti³⁺ which results in self-doping of TiO₂ and improves its photo-activity for hydrogen production. The obtained data were also employed to modify the previously proposed expanding photocatalytic area and overlap model to describe the effect of cocatalyst size and weight loading on photocatalyst activity. Comparing the trend of surface Ti³⁺ content increase and the photocatalytically promoted area, calculated with our model, suggests that the depletion zone formed around the heterojunction of Cu_xO–TiO₂ is the main active area for hydrogen production, and the hydrogen productivity of the photocatalyst depends on the surface coverage by this active area. However, the overlap of these areas suppresses the activity of the photocatalyst.

The depletion zone formed around the Cu_xO clusters is the main photocatalytically active area, and the H₂ production rate depends on surface coverage with this area; however, the overlap of these areas suppresses the photocatalyst activity.

Photocatalytic hydrogen evolution from biomass conversion

Biomass has incredible potential as an alternative to fossil fuels for energy production that is sustainable for the future of humanity. Hydrogen evolution from photocatalytic biomass conversion not only produces valuable carbon-free energy in the form of molecular hydrogen but also provides an avenue of production for industrially relevant biomass products. This photocatalytic conversion can be realized with efficient, sustainable reaction materials (biomass) and inexhaustible sunlight as the only energy inputs. Reported herein is a general strategy and mechanism for photocatalytic hydrogen evolution from biomass and biomass-derived substrates (including ethanol, glycerol, formic acid, glucose, and polysaccharides). Recent advancements in the synthesis and fundamental physical/mechanistic studies of novel photocatalysts for hydrogen evolution from biomass conversion are summarized. Also summarized are recent advancements in hydrogen evolution efficiency regarding biomass and biomass-derived substrates. Special emphasis is given to methods that utilize unprocessed biomass as a substrate or synthetic photocatalyst material, as the development of such will incur greater benefits towards a sustainable route for the evolution of hydrogen and production of chemical feedstocks.

Preparation and Characterization of Nanocrystalline TiO2 on Microsericite for High-Efficiency Photo-Energy Conversion of Methanol to Hydrogen

TiO2 and TiO2/sericite photocatalysts were successfully synthesized via the sol-gel method by adding a varying amount of acetic acid. The effect of acetic acid on TiO2 and TiO2/sericite photocatalysts was studied. The crystallite size, surface morphology, chemical composition, specific surface area, surficial functional groups, and light absorbance of the prepared photocatalysts were revealed by the analysis of X-ray diffraction (XRD), scanning electron microscope-energy dispersive spectrometry (SEM-EDS), nitrogen adsorption-desorption isotherms by using BET theory (Brunauer–Emmett–Teller), Fourier-transform infrared spectroscopy (FTIR), and UV-Vis absorption spectrometry. Photo-energy conversion of methanol to hydrogen was also conducted over the prepared photocatalysts. The best hydrogen production was achieved by using the TiO2/sericite photocatalyst to give a hydrogen production rate of 1424 μmol/g·h in 6 h of UV-light irradiation.