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The effect of electrode area, electrolyte concentration, temperature, and light intensity (up to 218 sun) on PV electrolysis of water is studied using a high concentrated triple-junction (3-J) photovoltaic cell (PV) connected directly to an alkaline membrane electrolyzer (EC). For a given current, the voltage requirement to run an electrolyzer increases with a decrease in electrode sizes (4.5, 2.0, 0.5, and 0.25 cm2) due to high current densities. The high current density operation leads to high Ohmic losses, most probably due to the concentration gradient and bubble formation. The EC operating parameters including the electrolyte concentration and temperature reduce the voltage requirement by improving the thermodynamics, kinetics, and transport properties of the overall electrolysis process. For a direct PV–EC coupling, the maximum power point of PV (Pmax) is matched using EC I–V (current–voltage) curves measured for different electrode sizes. A shift in the EC I–V curves toward open-circuit voltage (Voc) reduces the Pop (operating power) to hydrogen efficiencies due to the increased voltage losses above the equilibrium water-splitting potential. The solar-to-hydrogen (STH) efficiencies remained comparable (∼16%) for all electrode sizes when the operating current (Iop) was similar to the short-circuit current (Isc) irrespective of the operating voltage (Vop), electrolyzer temperature, and electrolyte concentration.

Both Pd and Au metal particles are used in photocatalytic hydrogen generation. Yet while both act as electron sink only gold is poised to respond to visible light due to its plasmonic response. In order to quantitatively gauge their relative contribution into the reaction, the photocatalytic H2 production, from Au/TiO2 and Pd/TiO2 catalysts was studied under UV and UV–Vis light. While under UV light excitation, a weak dependence on the work function of the metal is observed, under UV–Vis light, Au is found to be twice more active than Pd. Under identical UV–Vis light irradiation, the turn over frequency calculated from XPS at.% is found to be 2.8 and 1.8 s−1 for Au and Pd, respectively. The effect is far more pronounced when the rates are normalized to the number of particles of each metal. Both the semiconductor TiO2 (UV light) and the plasmonic metal (visible light) need to be excited for the enhancement to occur; visible light alone causes a negligible reaction rate. Photocurrent measurements further confirmed the difference in the photocatalytic activity under UV and UV–Vis light excitation. Moreover, because of the presence of Au particles responding to visible light the reaction rate is enhanced due to “light penetration depth” effect.

The facile synthesis of hierarchically functional, catalytically active, and electrochemically stable nanostructures holds a tremendous promise for catalyzing the efficient and durable oxygen evolution reaction (OER) and yet remains a formidable challenge. Herein, we report the scalable production of core-shell nanostructures composed of carbon-coated cobalt diphosphide nanosheets, C@CoP

A series of composite photocatalysts based on CdS nanorods decorated with Cu/Ni hydroxides were prepared via deposition precipitation method at room temperature (total metal loading ≈ 3 wt%). The performance of these photocatalysts was evaluated for H2 production through water dissociation reaction under direct sunlight. The 2.4Cu(OH)2 0.6Ni(OH)2/CdS photocatalyst with a total 3 wt% nominal metal cocatalyst loading demonstrated an excellent hydrogen production activity of ~20 mmol h−1 g−1, that is 2 and 20 times greater than the benchmark Au/CdS and pristine CdS photocatalysts, respectively. Detailed analyses based on UV–Visible diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), steady state photoluminescence (PL) and energy dispersive spectroscopy (EDS) suggested cocatalysts Cu/Ni hydroxides were transformed into their metallic states during photoreaction. Cu° was produced by the transfer of electrons due to the as available position of CdS conduction band (E° = 0.61 V) to surface Cu(OH)2 nanoclusters (Cu(OH)2/Cu°, E° = 0.224 V) whereas Ni° was produced by the shift in conduction band level of CdS under continuous sunlight illumination (Ni(OH)2/Ni°, E° = 0.72 V). Based on these observations, the mechanism of hydrogen production from water splitting over Cu/Ni(hydroxides)-CdS was described.

The photo-thermal reaction of ethanol to hydrogen and acetaldehyde over Ag/TiO2 is studied in flow conditions. Hydrogen production is mostly photo driven below 170 °C, and thermally driven above 250 °C. An increase in the overall reaction rates is observed when both photons and heat (photo-thermal effect) are present in the 125−225 °C temperature window for acetaldehyde and hydrogen production (via ethanol dehydrogenation; C2H5OH → CH3CHO + H2). The activation energies for photo-thermal and thermal reactions, measured in steady state conditions, are 31 and 40 kJmol−1, respectively. The maximum enhancement in reaction rates is 1.5× for acetaldehyde and 10× for hydrogen production. The enhancement for these two product should be the same. Reasons for these discrepancies are discussed. Other minor reaction products including ethylene and acetone appeared above 225 °C. Possible reasons for the enhanced rate of ethanol reaction under photo-thermal conditions, linked to plasmon resonance of Ag particles of Ag/TiO2, are discussed. Light to Chemical Energy Conversion (LCEC) was found equal to 0.12 % and 0.25 % at 170 °C and 225 °C, respectively.

This study compares the performance of 5 different Au/TiO 2 photocatalysts for H 2 production in alcohol–water mixtures under UV excitation, placing particular emphasis on the role of the TiO 2 support and alcohol sacrificial reagent. 1.5 wt.% Au/TiO 2 photocatalysts were prepared by the deposition–precipitation with urea method, using P25 TiO 2 (85% anatase and 15% rutile, 49 m 2 g −1 ), sol–gel anatase (39 m 2 g −1 ), hydrothermally synthesised anatase (115 m 2 g −1 ), commercial brookite (33 m 2 g −1 ) and hydrothermally synthesised rutile (29 m 2 g −1 ) as supports. UV–Vis, TEM, XRD, XPS and Au L 3 -edge EXAFS characterisation studies confirmed the presence of gold nanoparticles of mean size 5–10 nm on all the Au/TiO 2 photocatalysts, which generated intense localised surface plasmon resonances (LSPRs) centred between 560 and 590 nm. Gold nanoparticle deposition suppressed electron–hole pair recombination in each TiO 2 support following UV excitation, and created cathodic sites on TiO 2 for H 2 evolution. Photocatalytic H 2 production tests were conducted in water, methanol–water, ethanol–water, ethylene glycol–water and glycerol–water mixtures (alcohol concentration 10 vol.%) at a UV flux of 6.5 mW cm −2 . H 2 production rates decreased in the order Au/P25 > Au/anatase SG ≈ Au/brookite > Au/anatase HT ≫ Au/rutile HT when the rates were normalised against photocatalyst surface area. For each Au/TiO 2 photocatalyst, the rates decreased in the order glycerol > ethylene glycol > methanol > ethanol. Good correlations were established between H 2 production rates and the number of hydroxyl groups, polarity and relative hole scavenging ability of the alcohols. Results improve knowledge about the role of sacrificial reagents in photocatalytic hydrogen production.

The effect of Au particle size and loading (over TiO2 anatase and rutile) on the reaction selectivity and conversion of ethanol has been studied using temperature programmed desorption. The addition of Au onto TiO2 had three main effects on the reaction. First, a gradual decrease is observed in the reaction selectivity of the dehydration (to ethylene) in favor of dehydrogenation (to acetaldehyde) with increasing Au loading on both polymorphs of TiO2. Second, a gradual decrease is seen in the desorption temperature of the main reaction products also with increasing Au loading. Third, secondary reaction products [mainly C4 (crotonaldehyde, butene, furan) and C6 (benzene) hydrocarbons] increased considerably with increasing Au loading reaching about 60% for benzene for the 8 wt-%Au/TiO2 anatase. An inverse relationship between the interface lengths of Au particles on TiO2 and desorption temperatures of reaction products is found.

A field experiment was carried out on cowpea (Vigna unguiculata (L.) variety Kashi Kanchan during summer season at the experimental farm, department of Vegetable Science, College of Horticulture and Forestry, Central Agricultural University, Pasighat, Arunachal Pradesh. The experiment was laid out in factorial complete randomized block design with 12 treatments i.e. three levels of phosphorus [control 0 kg(P0), 20 kg (P1) and 40 kg (P2) /ha] and four levels of bio-fertilizer [control (B0), Rhizobium10 ml/kg seed(B1), PSB 10 ml/kg seed (B2) and Rhizobium + PSB both 10 ml/kg seed (B3)] with three replications. The uniform dose of nitrogen (N) and potassium (K) @ 20 kg/ha along with 10 t/ha FYM (Farm Yard Manure) were applied to all the treatments. Result indicated that the application of P2 (40 kg P/ha) significantly increased the plant height, leaf area index, stem girth, number of nodules per plant, number of branches per plant , total dry matter, pod yield, available soil nutrient status viz., pH, N, P, K, organic carbon and NPK content in plant after harvesting. Similarly, seed inoculation with B3 (Rhizobium + PSB) significantly enhanced the growth, yield, soil nutrient status and nutrient content in plant over single inoculation of Rhizobium and PSB. Combined inoculation of seed with Rhizobium + PSB (B3) along with 40 kg P/ha (P2) significantly increased the stem girth (1.84 cm), total dry matter (13.91g/plant), green pod yield (196.37g/plant and 120.90q/ha), soil nutrient status viz., pH(6.20), available N (370.89 kg/ha), available P (38.57 kg/ha), available K (168.77 kg/ha), organic carbon (2.80%) and N, P and K (0.17%, 0.16% and 0.39%) content over rest of treatment combination.

Catalytic hydrogen production from renewables is a promising method for providing energy carriers in the near future. Photocatalysts capable of promoting this reaction are often composed of noble metal nanoparticles deposited on a semiconductor. The most promising semiconductor at present is TiO₂. The successful design of these catalysts relies on a thorough understanding of the role of the noble metal particle size and the TiO₂ polymorph. Here we demonstrate that Au particles in the size range 3-30 nm on TiO₂ are very active in hydrogen production from ethanol. It was found that Au particles of similar size on anatase nanoparticles delivered a rate two orders of magnitude higher than that recorded for Au on rutile nanoparticles. Surprisingly, it was also found that Au particle size does not affect the photoreaction rate over the 3-12 nm range. The high hydrogen yield observed makes these catalysts promising materials for solar conversion.

The work presents the dark and photocatalytic reactions of ethanol over Au particles deposited on TiO2 anatase nano (≤10 nm) and micro (ca. 0.15 μm) particle catalysts. The Au particles are of uniform and similar dimension (mean particle size = ca. 5 and 7 nm on the micro– and nano-sized TiO2, respectively). XPS Au4f indicated that in both cases Au particles are present in their metallic state with no evidence of charge transfer to (or from) the semiconductor. Under dark conditions, ethanol adsorption leads to stable ethoxide species (from in situ Infrared analysis) up to ca. 550 K at which point conversion to acetaldehyde by dehydrogenation and ethylene by dehydration occurs (from temperature programmed desorption (TPD) analysis). Liquid slurry photoreaction indicated the production of hydrogen with a rate ≈2 L/kgCatal min on 2 wt.% Au/TiO2 anatase nanoparticles under UV photo irradiation of comparable intensity to solar radiation. While the reaction rate per unit mass was lower on the micro-sized Au/TiO2, it simply scaled up to an equivalent rate for the nano-sized Au/TiO2 catalyst when normalised by unit area, indicating the absence of a particle size effect of the semiconductor on the electron transfer reaction within the range 10–150 nm).

Menthol mint oil is distilled by water steam distillation from leaves of Mentha arvensis and is the most importance source of L-menthol. It contains L-menthol 68.3%, menthone 8.2%, isomenthone 4.4%, menthyl acetate 4.3%, mixture of isomers of menthol 4.5%, cis-3- hexanal 0.2-% and limonene 1.2%, However percentage of components depends on the genetic and ecological conditions. Major component L-Menthol is isolated by freezing at low temperature with the recovery of around 65% in form of menthol flakes and the remaining material is known as DMO or dementholised oil (30%). During the process 1% loss is generally found. All the components are being used in Flavours, Pharmaceuticals, Tobacco and other cosmetic Industries.

The review deals with the principles of photoreactions over TiO2 with emphasis on both single crystals and nano particles. The main fundamental reactions of prototype organic compounds are given and analysed. Hydrogen production from alcohols as an example of sustainable production of energy carriers is also presented and discussed. After an overview of the principles of adsorption and reaction of ethanol (as an example of bio–fuel) over TiO2 single crystals the focus is on production of hydrogen over TiO2 nano–particles in presence of transition metals. A comparison of the merit of a series of transition metals with respect to their activity in electron capture from the conduction band and subsequent transfer during hydrogen photo–production is also given. The review ends by giving two main examples of the effect of Au/TiO2 and Pd/TiO2 for the production of hydrogen from linear alcohols.