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Biomass, a naturally abundant, sustainable and clean resource has great potential as an alternative to replace the limited fossil feedstock for value‐added chemicals and fuels. Biomass with abundant reductive functional groups could theoretically act as electron donor to consume photogenerated holes and/or active free radicals. Biomass photoreforming over semiconductor photocatalysts using solar light as energy input attracts much attention in this context. However, biomass photoreforming still suffers low conversion efficiency and product selectivity due to its structural complexity, poor solubility and unclear reaction mechanism. Owing to the advanced features of mass diffusion of biomass derivatives and adjustable surface properties, hierarchically porous photocatalysts with desired active sites at each length scale of porosity have shown their superiority in boosting the conversion efficiency and selectivity of biomass photoreforming. Herein, a critical review is presented on selective biomass photoreforming for simultaneous H2 and value‐added chemicals co‐production on hierarchically porous photocatalysts. The fundamentals of biomass photoreforming and current bottleneck of biomass valorization by photocatalytic process are presented and analyzed. The rational photocatalyst design with hierarchically porous structure to improve the biomass conversion and product selectivity by boosting mass transfer is highlighted. Finally the challenges and opportunities for photocatalytic biomass valorization are presented in the perspective ssection. [ABSTRACT FROM AUTHOR]

Solar-driven hydrogen (H) generation utilizing photocatalysts has received extensive attention because of its potential to mitigate the global energy crisis and environmental problem. The implementation of efficient H production strongly relies on stable, active, and low-cost photocatalysts. In this work, we report the designed synthesis of macroporous ZnO/ZnS/CdS composite spheres as a highly active photocatalyst for H production via solar-driven water splitting. The composite spheres were synthesized by a facile solvothermal reaction paired with controllable ion-exchange processes. The resulting material exhibits superior photocatalytic activity, delivering a high H production rate of ~11.37 mmol h g under light illumination (250-780 nm, with an ultraviolet light intensity of 34 mW cm and visible light intensity of 158 mW cm). Such performance enhancement can be mainly ascribed to the synergic effects of the composite structure: (1) formation of coherent ZnO/CdS and ZnS/CdS heterojunctions at nanoscale, facilitating charge separation of photoinduced electron/hole pairs, (2) highly accessible inner surface of the meso/macroporous ZnO/ZnS/CdS composites for rapid mass transfer of electrolyte, and (3) enhanced visible light scattering capability induced by their large particle size. [ABSTRACT FROM AUTHOR]

[Display omitted] Solar-light driven oxidation of benzylic alcohols over photocatalysts endows significant prospects in value-added organics evolution owing to its facile, inexpensive and sustainable process. However, the unsatisfactory performance of actual photocatalysts due to the inefficient charge separation, low photoredox potential and sluggish surface reaction impedes the practical application of this process. Herein, we developed an innovative Z-Scheme Cs 3 BiBr 9 nanoparticles@porous C 3 N 4 tubes (CBB-NP@P-tube-CN) heterojunction photocatalyst for highly selective benzyl alcohol oxidation. Such composite combining increased photo-oxidation potential, Z-Scheme charge migration route as well as the structural advantages of porous tubular C 3 N 4 ensures the accelerated mass and ions diffusion kinetics, the fast photoinduced carriers dissociation and sufficient photoredox potentials. The CBB-NP@P-tube-CN photocatalyst demonstrates an exceptional performance for selective photo-oxidation of benzylic alcohol into benzaldehyde with 19, 14 and 3 times higher benzylic alcohols conversion rate than those of C 3 N 4 nanotubes, Cs 3 Bi 2 Br 9 and Cs 3 Bi 2 Br 9 @bulk C 3 N 4 photocatalysts, respectively. This work offers a sustainable photocatalytic system based on lead-free halide perovskite toward large scale solar-light driven value-added chemicals production. [ABSTRACT FROM AUTHOR]

[Display omitted] The conversion of CO 2 into syngas, a mixture of CO and H 2 , via photocatalytic reduction, is a promising approach towards achieving a sustainable carbon economy. However, the evolution of highly adjustable syngas, particularly without the use of sacrifice reagents or additional cocatalysts, remains a significant challenge. In this study, a step-scheme (S-scheme) 0D ZnGa 2 O 4 nanodots (∼7 nm) rooted g-C 3 N 4 nanosheets (denoted as ZnGa 2 O 4 /C 3 N 4) heterojunction photocatalyst was synthesized vis a facial in-situ growth strategy for efficient CO 2 -to-syngas conversion. Both experimental and theoretical studies have demonstrated that the polymeric nature of g-C 3 N 4 and highly distributed ZnGa 2 O 4 nanodots synergistically contribute to a strong interaction between metal oxide and C 3 N 4 support. Furthermore, the desirable S-scheme heterojunction in ZnGa 2 O 4 /C 3 N 4 efficiently promotes charge separation, enabling strong photoredox ability. As a result, the S-scheme ZnGa 2 O 4 /C 3 N 4 exhibited remarkable activity and selectivity in photochemical conversion of CO 2 into syngas, with a syngas production rate of up to 103.3 μ mol g−1 h−1, even in the absence of sacrificial agents and cocatalyst. Impressively, the CO/H 2 ratio of syngas can be tunable within a wide range from 1:4 to 2:1. This work exemplifies the effectiveness of a meticulously designed S-scheme heterojunction photocatalyst for CO 2 -to-syngas conversion with adjustable composition, thus paving the way for new possibilities in sustainable energy conversion and utilization. [ABSTRACT FROM AUTHOR]

ZnO is known to be photocatalytic, but with limited performances due to the strong electron-hole recombination after irradiation. The integration of ZnO nanomaterials on a conductive and high surface area carbon substrate is thus a potential alternative to obtain a significant improvement of the photocatalytic performance. Moreover, the carbon functionalization is expected to have a significant role in the adsorption/degradation mechanisms of dye, due to the difference in wettability or surface charge. In this view, ZnO photocatalytic nanoparticles have been deposited on high surface area carbon xerogel substrate (C XG), using a new and original plasma process, consisting in the degradation of a solid organometallic directly on the carbon substrate (no gaseous precursor). In addition to the ZnO nanoparticle formation, the plasma treatment allows the carbon functionalization. The ZnO/C XG composite has been tested for the degradation of Rhodamine B (RhB) in aqueous media and compared with and O 2 or NH 3 plasma-treated xerogels (without nanoparticles) to identify the significant role of the substrate and its modification in the RhB adsorption and degradation mechanism. The high photocatalytic activity of ZnO/C XG composite is attributed to (i) the formation of small (8–10 nm) and well-crystallized ZnO nanoparticles anchored to the carbon substrate and (ii) to the modification of the xerogel surface chemistry. Indeed, O 2 plasma treatment of the C XG promotes the generation of hydroxyl, carbonyl and carboxyl surface functional groups, which are polar and acidic, while the NH 3 plasma treatment mainly leads to the formation of polar and basic amino groups. While both plasma treatments promote the formation of polar functional groups, which enhance the C XG wettability, the formation of acidic groups is identified as beneficial for the adsorption of the RhB dye, while basic groups are detrimental. [ABSTRACT FROM AUTHOR]

Abstract A theoretical investigation of optical proprieties of three nanostructures such as BiOV 4 /3DOM TiO 2 , ZnO/3DOM TiO 2 and BiOV 4 /3DOM ZnO has been presented and discussed. The study based on a one band effective mass approximation model was developed to calculate the charge carrier energies on various parameters of nanostructures including their size. We computed the optical properties for both spherical BiVO 4 and ZnO nanoparticles incorporated in the three dimensionally ordered macroporous inverse opal TiO 2 nanocomposites (3DOM-TiO 2). At first and by solving a three dimension Schrödinger equation we calculated the dependence of charge carriers energies on the size of nanoparticles. Then we investigated the variation of the excitonic energy of BiOV 4 /3DOM-TiO 2 , ZnO/3DOM-TiO 2 and BiOV 4 /3DOM-ZnO as function of the radius of these nanostructures into taken account the effects of dielectric and coulomb interaction between charge carriers. We showed that the radiative recombination lifetime is enhanced with decreasing BiVO 4 and ZnO quantum dots (QDs) size. It was found that as the size of the dot is reduced the confinement of charge carriers and the optical gap are increased. The optical gap of the ZnO/3DOM-TiO 2 is larger than both BiOV 4 /3DOM-TiO 2 and BiOV 4 /3DOM-ZnO especially for small radius. It was also found that radiative life time in the BiOV 4 /3DOM-TiO 2 , ZnO/3DOM-TiO 2 and BiOV 4 /3DOM-ZnO increased by increasing the radius of these nanostructures. In addition, we have also showed that, the radiative lifetime in the ZnO/3DOM-TiO 2 nanostructure is less than both BiOV 4 /3DOM-TiO 2 and BiOV 4 /3DOM-ZnO nanostructures. Finally, we have studied and discussed the Auger process in BiOV 4 /3DOM-TiO 2 , ZnO/3DOM-TiO 2 and BiOV 4 /3DOM-ZnO nanostructures. At first, we have showed that the auger process is important when the radiuses of nanostructures are less than 2 nm. Then we have also showed that this process is more important for ZnO/3DOM-TiO 2 compared to the other nanostructures. Graphical abstract We focus our theoretical study on the radiative and Auger recombination lifetime in BiVO 4 /3DOM-TiO 2 , ZnO/3DOM-TiO 2 and BiVO 4 /3DOM-ZnO nanocomposites. Image 1 Highlights • Novel nanocompsites BiVO 4 /3DOM-TiO 2 , ZnO/3DOM-TiO 2 and BiVO 4 /3DOM-ZnO has been realized for the photocatalysis. • We calculate the radiative recombination lifetime in BiVO 4 /3DOM-TiO 2 , ZnO/3DOM-TiO 2 and BiVO 4 /3DOM-ZnO nanocomposites. • We calculate the Auger recombination lifetime in BiVO 4 /3DOM-TiO 2 ZnO/3DOM-TiO 2 and BiVO 4 /3DOM-ZnO nanocomposites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zn 0.1 Cd 0.9 S/NiS heterojunction photocatalysts is synthesized by in situ growth NiS nanoparticles on Zn 0.1 Cd 0.9 S nanorods. • The synergistic effect of NiS and ZCS largely improves the absorption and utilization of light. • The photogenerated electrons transfer from NiS to ZCS to effectively separate the photogenerated carriers. • The optimized photocatalyst exhibits high photocatalytic H 2 production performance (12.77 mmol g−1h−1) and high lactic acid selectivity (95%). The well-designed photocatalyst is a reasonable strategy to realize the photocatalytic H 2 -production and biomass conversion. In this work, the noble-metal-free Zn 0.1 Cd 0.9 S/NiS (SNS) composite was successfully prepared by in-situ chemical bath deposition of NiS nanoparticles on Zn 0.1 Cd 0.9 S (ZCS) nanorods surface for photocatalytic H 2 -production using glucose as electron donors for effective utilization of holes. Our results show that the synergistic effect of NiS and ZCS largely improves the absorption and utilization of light, and the photogenerated electrons transfer from NiS to ZCS to effectively separate the photogenerated carriers for the enhanced photocatalytic H 2 -production as the one-dimensional nanorods is conducive to the transmission of photogenerated carriers. The optimized catalyst (SNS20) has the highest H 2 production rate (12.77 mmol·g−1·h−1), which is 6.7 times that of pure ZCS nanorods. In particular, its apparent quantum efficiency (AQE) at 350 nm reaches 12.74%. The glucose conversion increases from 25.7% to 49.9% and lactic acid selectivity reaches 95%. During three cycles, the SNS20 shows the stable H 2 -production rate, which remains 12 mmol·g−1·h−1 after three cycles. And the glucose conversion still remains above 40%. This work provides a reasonable strategy for designing heterojunction photocatalyst to improve the performance for the synergy of photocatalytic H 2 -production and biomass conversion. [ABSTRACT FROM AUTHOR]

A series of BiVO 4 /3DOM TiO 2 nanocomposites have been synthesized and their photocatalytic activity was investigated under visible light irradiation using the RhB dye as model pollutant molecule in an aqueous solution. The effect of the amount of BiVO 4 as visible light sensitizer on the photocatalytic activity of BiVO 4 /3DOM TiO 2 nanocomposites was highlighted. The heterostructured composite system leads to much higher photocatalytic efficiencies than bare 3DOM TiO 2 and BiVO 4 nanoparticles. As the proportion of BiVO 4 in BiVO 4 /3DOM TiO 2 nanocomposites increases from 0.04 to 0.6, the photocatalytic performance of the BiVO 4 /3DOM TiO 2 nanocomposites increases and then decreases after reaching a maximum at 0.2. This improvement in photocatalytic perfomance is related to 1) the interfacial electron transfer efficiency between the coupled materials, 2) the 3DOM TiO 2 inverse opal structure with interconnected pores providing an easy mass transfer of the reactant molecules and high accessibility to the active sites and large surface area and 3) the effect of light sensitizer of BiVO 4 . Intensive studies on structural, textural, optical and surface properties reveal that the electronic interactions between BiVO 4 and TiO 2 lead to an improved charge separation of the coupled BiVO 4 /TiO 2 system. The photogenerated charge carrier densities increase with increasing the BiVO 4 content, which acts as visible light sensitizer to the TiO 2 and is responsible for the enhancement in the rate of photocatalytic degradation. However, the photocatalytic activity is reduced when the BiVO 4 amount is much higher than that of 3DOM TiO 2 . Two reasons could account for this behavior. First, with increasing BiVO 4 content, the photogenerated electron/hole pairs are accumulated at the surface of the BiVO 4 nanoparticles and the recombination rate increases as shown by the PL results. Second, decreasing the amount of 3DOM TiO 2 in the nanocomposite decreases the surface area as shown by the BET results. Moreover, the poor adsorptive properties of the BiVO 4 photocatalyst also affect the photocatalytic performance, in particular at higher BiVO 4 content. The present work demonstrates that BiVO 4 /3DOM TiO 2 is a very promising heterojunction system for visible light photocatalytic applications. [ABSTRACT FROM AUTHOR]

Three dimensionally ordered macroporous inverse opal TiO 2 nanocomposites decorated by ZnO quantum dots (ZnO QDs@3DOM TiO 2 ) with an intimate contact were successfully synthesized using the sol-gel technique and characterized in terms of structure, porosity, chemical composition and optical properties. The photocatalytic activity of ZnO QDs@3DOM TiO 2 nanocomposites with different ZnO QDs amounts was evaluated in the aqueous phase of dye pollutant molecules and compared with the state-of-the-art 3DOM TiO 2 and P25 photocatalysts. The symbiotic effect of ZnO QDs and 3DOM photonic structure on the light absorption and further on the photocatalytic activity of the nanocomposites was observed. The sample with the highest ZnO QDs amount exhibits extraordinarily high photocatalytic activity, which is attributed to firstly, the formation of an intimate junction between the two semiconductors, hence favoring the separation of photo-introduced electron–hole pairs in ZnO-TiO 2 photocatalyst, and, secondly, to the quantum size effect (QSE). The QSE results in an increase in the width of the forbidden electronic band, which increases the energy of electrons (holes) in the conduction (valence) and particularly leads to the displacement of the conduction band potentials of ZnO to more negative energy values compared to TiO 2 . Thanks to the heterojuction formed between ZnO QDs and 3DOM TiO 2 , the energy difference between conduction bands of both semiconductors acts as a driving force for rapid electron/hole transfer between the coupled materials. Due to the extremely short diffusion time, the lifetime of photogenerated charge carriers is extended and the effectiveness of reduction and oxidation process is increased with faster reaction kinetics. Increasing the amount of ZnO QDs can boost the photocatalytic activity. On the other hand, 3DOM photonic structure of TiO 2 with its open meso-macroporosity can facilite the diffusion of dye molecules and light propagation. This first successful example of symbiose of a series of physical effects can open a new window for solar energy conversion by the synergitic association of QSEs, photonic effect and other effects such as plasmonic effects, in one solid material to develop highly efficient solar light havesting system to enhance solar energy conversion effeciency for photocatalysis and photovoltaics. [ABSTRACT FROM AUTHOR]

CdS is a very good visible-light responsive photocatalyst for hydrogen production. However, the fast recombination of photogenerated electron-hole pairs and quick photocorrosion limit its application in photocatalysis. To address these problems, we herein have designed and synthesized monodisperse polyaniline@cadmium sulfide (PANI@CdS) core-shell nanospheres to probe the mechanisms of photocorrosion inhibition and photocatalytic H 2 production. All the PANI@CdS core-shell nanospheres demonstrate highly enhanced photocorrosion inhibition and photocatalytic hydrogen production comparing to the pure CdS nanospheres. Particularly, the PANI@CdS core-shell nanospheres with the thinnest PANI shell possess the highest hydrogen production rate of 310 μmol h −1 g −1 in 30 h without deactivation. Our results reveal that the newly formed C S and/or N Cd bonds in PANI@CdS prevent the reduction of the surface sulfide ions to sulphur, leading to effective photocorrosion inhibition. Our results also verify that the photogenerated holes migrating from valence band (VB) of CdS to the highest occupied molecular orbital (HOMO) of PANI leads to the enhanced photocatalytic hydrogen production. This work can shed some light on the mechanism of conducting polymers modifying metal sulfides for effective photocorrosion inhibition and highly enhanced photocatalytic activities. [ABSTRACT FROM AUTHOR]

A ternary photocatalyst TiO 2 -Au-CdS based on three-dimensionally ordered macroporous TiO 2 (3DOM TiO 2 ) was successfully prepared to enhance the light absorption, extend the light responsive region, reduce the recombination rate of charge carriers and promote the efficiency of water splitting H 2 evolution ultimately. The obtained 3DOM TiO 2 -Au-CdS powder has a pure anatase phase of TiO 2 and greenockite structured CdS according to the XRD results and TEM analysis. Au nanoparticles (AuNPs) and CdS were evenly distributed in the 3DOM structure which enhances H 2 -generation rate under visible light by improving light harvesting and utilizing its mass transfer facilitation. As a result, the hydrogen generation rate (1.81 mmol h −1 g −1 ) using 3DOM TiO 2 -Au-CdS photocatalyst under visible light irradiation was 13-fold higher than the binary 3DOM TiO 2 -CdS reference photocatalyst. Under ultraviolet-visible light, the photogenerated electrons in TiO 2 would be transferred to recombine with the holes of CdS and under visible light, electrons would move to the conduction band (CB) of TiO 2 from CdS via AuNPs. The two different types of internal electron-transfer process in the ternary photocatalyst under ultraviolet and visible light were proposed respectively and both would efficiently reduce the recombination rate of photogenerated electrons and holes thus stimulate H 2 evolution rate. The present work demonstrated an excellent example of the synergistic effect of the light absorption enhancement by 3DOM structure, the photosensitizing and electron reservoir effect of AuNPs and the reduction of recombination rate of charge carriers by CdS to highly promote the photocatalytic activity in water splitting reaction. [ABSTRACT FROM AUTHOR]

Abstract: The photocatalytic activities of various hierarchically meso–macroporous titanias, obtained via a spontaneous self-formation process using titanium isopropoxide, have been investigated by comparing each materials’ capability to photodegrade Rhodamine B. Three synthesis routes have been developed to synthesize hierarchically meso–macroporous titania materials: (A) in water without and (B) with hydrothermal treatment and (C) in a surfactant Brij 56 aqueous solution with hydrothermal treatment, respectively. These results show that the introduction of surfactant Brij 56 and a hydrothermal treatment in the synthesis system greatly improve the crystallinity of the anatase phase in hierarchically meso–macroporous titanias and their thermal stability, resulting in a remarkable enhancement of their photocatalytic activity. Furthermore, the effect of calcination on hierarchically porous structure and their photocatalytic activity has also been investigated in detail. The properties of the products were characterized by XRD, SEM and N2 adsorption-desorption measurements. [Copyright &y& Elsevier]