Apparent Quantum Yield Values Research Articles

Heterointerface and crystallinity engineering of Ru/RuS2 dual co-catalysts for enhanced photocatalytic hydrogen evolution

In this paper, the Ru/RuS2 nanoparticles as dual co-catalysts were self-assembled on the surface of g-C3N4 nanotubes (Ru/RuS2/g-C3N4 NTs) for photocatalytic H2 production. The Ru/RuS2/g-C3N4 NTs showed greatly enhanced photocatalytic H2 production activity (1409 μmol·g−1·h−1), 1.16 times of RuS2/g-C3N4 NTs (1212 μmol·h−1·g−1), 10.51 times of Ru/g-C3N4 NTs (134 μmol·g−1·h−1), and 82.88 times of the pure g-C3N4 NTs (17 μmol·g−1·h−1). Besides, the apparent quantum yield value (AQE) of Ru/RuS2/g-C3N4 NTs is 3.92% at 370 nm. Ru/RuS2 as dual co-catalysts are self-assembled on the surface of g-C3N4 NTs and show strong electronic synergistic interaction between the interfaces, reduce ΔGH* of RuS2 and desorption energy of Ru, and promote the selectivity and activity of HER kinetically and thermodynamically respectively, which exhibits higher photogenerated carrier concentration and lower charge migration resistance than RuS2 and Ru, showing the synergistic effect to facilitate the generation and migration of carriers and provides active sites for photocatalysis.

Boosting surface charge transfer by aldehyde group grafted on loofah-sponge-like carbon nitride for visible light H2 evolution

Although graphitic carbon nitride (g-C3N4) has broad prospects to resolve the energy crisis, but the rational design of catalyst with high photocatalytic efficiency remains a great challenge. Herein, the hollow porous loofah-sponge-like g-C3N4 incorporated with aldehyde group (LS-ACNx) was achieved via supramolecular self-assembly and thermal polymerization. The detailed characterization results indicated that the excellent performance was primarily attributed to the aldehyde group modification and hollow porous loofah-sponge-like structure. The aldehyde groups herein not only dramatically improve the interface charge transfer and suppress charge recombination, but also adjust the band structure and negative shift the conduction band position. The charge carries concentration of LS-ACN15 was 1.6 times higher relative to bulk g-C3N4 (CN). In addition, the hollow porous loofah-sponge-like morphology enhanced the specific surface area and light-harvesting ability. Benefiting from these, the obtained LS-ACN15 photocatalyst exhibited the superior photocatalytic H2 evolution performance of (10.5 ± 0.6) mmol g-1h−1, which was 96 times higher than that of the CN (0.109 mmol g-1h−1), and outperformed the majority of the previously g-C3N4-based photocatalysts. Particularly, the apparent quantum yield value was reached to be 16.8 % at 420 nm for LS-ACN15 photocatalyst. This work provides insights into constructing high performance catalysts by tuning energy band structure and charge transfer for energy and environment related field applications.

Inter‐laboratory differences in the apparent quantum yield for the photochemical production of dissolved inorganic carbon in inland waters and implications for photochemical rate modeling

AbstractSolar radiation initiates photochemical oxidation of dissolved organic carbon (DOC) to dissolved inorganic carbon (DIC) in inland waters, contributing to their carbon dioxide emissions to the atmosphere. Models can determine photochemical DIC production over large spatiotemporal scales and assess its role in aquatic C cycling. The apparent quantum yield (AQY) spectrum for photochemical DIC production, defined as mol DIC produced per mol chromophoric dissolved organic matter‐absorbed photons, is a critical model parameter. In previous studies, the principle for the determination of AQY spectra is the same but methodological specifics differ, and the extent to which these differences influence AQY spectra and simulated aquatic DIC photoproduction is unclear. Here, four laboratories determined AQY spectra from water samples of eight inland waters that are situated in Alaska, Finland, and Sweden and span a nearly 10‐fold range in DOM absorption coefficients. All AQY values fell within the range previously reported for inland waters. The inter‐laboratory coefficient of variation (CV) for wavelength‐integrated AQY spectra (300–450 nm) averaged 38% ± 3% SE, and the inter‐water CV averaged 63% ± 1%. The inter‐laboratory CV for simulated photochemical DIC production (conducted for the five Swedish lakes) averaged 49% ± 12%, and the inter‐water CV averaged 77% ± 10%. This uncertainty is not surprising given the complexities and methodological choices involved in determining DIC AQY spectra and needs to be considered when applying photochemical rate modeling. Thus, we also highlight current methodological limitations and suggest future improvements for DIC AQY determination to reduce inter‐laboratory uncertainty.

Efficient visible-light-driven hydrogen evolution over ternary MoS2/Pt[sbnd]TiO2 photocatalysts with low overpotential

By surface-decorating PtTiO2 hybrid catalyst with MoS2 nanosheets, we prepared a new MoS2/PtTiO2 ternary system as high-performance photocatalysts. The ternary MoS2/PtTiO2 outperforms both the binary MoS2TiO2 and PtTiO2 systems in photocatalytic hydrogen evolution with an AQY (apparent quantum yield) value of 12.54% at 420 nm, owing to the unique ternary design that creates more efficient electron transport path and electron-hole separation mechanism. Electrochemical characterization showed that the MoS2/PtTiO2 ternary electrode afford an efficient pathway of photo-excited electrons from TiO2 to surface-decorated Pt nanoparticles using MoS2 and internal Pt nanoparticles as bridges, thus significantly promoting electron transfer, reducing the system overpotential and leading to the activation of more reactive sites. This internal electron transfer pathway (TiO2 → Pt (internal) → MoS2 → Pt (surface)) eliminates the need of other metal cocatalysts because the Pt nanoparticles play two roles of storing the conduction band electrons of TiO2 and acting as co-catalyst for reduction of protons to hydrogen. This unique ternary metal-semiconductor heterojunction for efficient photocatalytic hydrogen evolution provides a meaningful reference for reasonable design of other hybrid photocatalysts.

Photosensitization of zinc phthalocyanine bearing 15-crown-5 ether moieties on carbon nitride for H2 production: Effect of co-existing alkali metal ions

A zinc phthalocyanine derivative (ZnPc) with one carboxyl group and three 15-crown-5 ether moieties has been synthesized and used as photosensitizer of Pt-loaded graphitic carbon nitride (Pt/g-C3N4) for visible-light-driven H2 production. By adding alkali metal ions (Li+, Na+, or K+) in the ZnPc solution before the dye-sensitization process, the photosensitization for H2 production on Pt/g-C3N4 can be improved with an increasing sequence of Li+ < Na+ < K+. Especially, the co-existing K+ ions cause the H2 production activity enhancing from 163 to 476 μmol h−1 with a turnover number (TON) from 3105 to 9067 h−1. Besides, the coexisting Li+, Na+ and K+ ions exhibiting an impressive apparent quantum yield (AQY) of 2.06%, 2.41% and 2.74% at 700 nm, respectively. All those AQY values are higher than that (1.88%) of the ZnPc-Pt/g-C3N4 without addition of alkali metal ion. The further investigation results indicate that the combination of ZnPc's 15-crown-5 ethers with ions are able to enhance the electron transfer ability and then the photoactivity for H2 production. Our finding may open a way to highly efficient dye-sensitized semiconductor-based photocatalysis for solar energy conversion by using ZnPc derivative bearing purposeful substituents which can be interacted with proper ions.

A new route for visible/near-infrared-light-driven H2 production over titania: Co-sensitization of surface charge transfer complex and zinc phthalocyanine

This work introduces a new strategy for visible/near-infrared (NIR) light responsive H2 production over TiO2 nanoparticles co-sensitized with zinc phthalocyanine derivative (Zn-tri-PcNc) and surface ligand-to-metal charge transfer (LMCT) complex, which is in situ formed on the TiO2 nanoparticles' surfaces by using ascorbic acid (AA). The in situ formed surface LMCT complex (AA-TiO2) exhibits obvious visible-light-responsive photoactivity (126.2 μmol/h) for H2 production with a high apparent quantum yield (AQY) of 16.1% at 420 nm monochromatic light irradiation. Moreover, the co-sensitized TiO2 nanoparticles (Zn-tri-PcNc-TiO2-AA) shows a much higher photoactivity (162.2 μmol/h) for H2 production than the surface LMCT complex, and broader spectral responsive region (400–800 nm) with a relatively high AQY value (0.97%) at 700 nm monochromatic light irradiation. The present result reveals a possible substitute for the conventional Ru(II)-bipyridyl complexes or organic dyes as sensitizer of semiconductors in the field of solar fuel conversion.

Highly efficient photocatalytic hydrogen generation by solution-processed ZnO/Pt/CdS, ZnO/Pt/Cd1−xZnxS and ZnO/Pt/CdS1−xSex hybrid nanostructures

Photocatalytic generation of hydrogen by using the hybrid nanostructures, ZnO/Pt/CdS, ZnO/Pt/Cd1−xZnxS and ZnO/Pt/CdS1−xSex, has been studied under UV-visible and visible irradiation by employing Na2S and Na2SO3 as hole scavengers. Good H2 evolution rates up to 17.4 mmol h−1 g−1 and an apparent quantum yield (AQY) of 11.1% were obtained with ZnO/Pt/CdS under UV-visible irradiation. With the visible irradiation alone, the rate of H2 production was slower. With 20% Zn substitution in place of Cd in CdS, the rate of H2 generation was 31.2 mmol h−1 g−1 and 12.5 mmol h−1 g−1 respectively with UV-visible and visible irradiation, the corresponding AQY values being 23.1% and 18%. With 50% substitution of S by Se in CdS, the rate of hydrogen generation was at 19 mmol h−1 g−1 and 16 mmol h−1 g−1 with UV-visible and visible irradiation respectively, but the AQY values were in the range of 8–9%. Replacing Na2S and Na2SO3 by benzyl alcohol as the scavenger improves the catalytic activity of ZnO/Pt/CdS yielding H2 at the rate of 31.6 mmol h−1 g−1 and AQY of 34.5% under visible irradiation. The results were even more remarkable with ZnO/Pt/Cd0.8Zn0.2S where the rate was 36.5 mmol h−1 g−1 and the AQY reached 50.4% with visible irradiation. A noteworthy feature of the present study is that the hybrid nanostructures were prepared by simple solution processing involving sequential addition of reagents to ZnO nanoparticles in methanol medium.

薇甘菊萎蔫病毒感染对薇甘菊光合特性和4种酶活性的影响

Mikania micrantha(Compositae) is one of the world′s most aggressive weeds and is responsible for substantial damage caused to natural ecosystems and biodiversity in South china.A new virus infecting Mikania micrantha,designated Mikania micrantha wilt virus(MMWV),belongs to a third subgroup of the genus Fabavirus and represents a distinct new isolate of Gentian mosaic virus(GeMV).Although MMWV is not lethal to M.micrantha,MMWV efficiently inhibits the growth of its host under both laboratory and field conditions.The feasibility of using MMWV to control M.micrantha is therefore worth exploring further.To gain further understanding concerning the physiological and biochemical effects of MMWV infection on Mikania micrantha,the activities of superoxide dismutase(SOD),peroxidase(POD),phenylalanine ammonia-lyase(PAL),polyphenol oxidase(PPO),as well as chlorophyll a/b ratios,total chlorophyll content,and photosynthetic activity were evaluated in M.micrantha leaf tissues following MMWV infection.In comparison with uninfected control leaves,our results revealed that chlorophyll a,b and total chlorophyll contents,and the ratio of chlorophyll a/b decreased by 30.76%,18.76%,26.41% and 17.84%,respectively,by 32 d post-MMWV infection.SOD activity significantly increased and reached maximal levels within 16 d post-infection,however activities at 24 and 32 d were 13.28% and 25.37% lower than those of control(uninfected) plants,respectively.POD activities were significantly higher in leaves of inoculated plants relative to control plants throughout the experimental period,with maximal levels occurring by 24 d post-infection.POD activities at 16,24 and 32 d post-infection were increased by 16.70%,41.12% and 16.11%,respectively,relative to levels observed in control plants.The activity of PPO in infected M.micrantha leaves reached maximal levels at 8 d post-infection,increasing to 77.75% above control levels,however PPO levels were 14.27% below control levels by 32 d.PAL activities following MMWV infection exhibited a pattern similar to that observed for PPO,increasing to 23.58% above control levels,then subsequently declining to 20.53% below control levels,at 8 and 32 d day post-infection,respectively.Maximal net photosynthetic rate(Pmax),dark respiration rate(Rd),light compensation point(LCP),light saturation point(LSP) and apparent quantum yield(AQY) were 11.76 μmol·m-2·s-1,-2.23 μmol·m-2·s-1,42.56 μmol·m-2·s-1,1063.92 μmol·m-2·s-1 and 0.04 μmol/μmol,respectively,in MMWV-infected leaves at 32 d post-infection.In contrast,Pmax,Rd,LCP,LSP and AQY values were 17.37 μmol·m-2·s-1,-2.43μmol·m-2·s-1,36.21 μmol·m-2·s-1,1216.13 μmol·m-2·s-1 and 0.05 μmol/μmol,respectively,in uninfected leaves at 32 d.In comparison with control leaves,Pmax and LSP values declined by 32.34 and 12.52% following MMWV infection,however,Rd,LCP and AQY values showed no significant change during the experimental period.Our results provide key information concerning the reduction of photosynthetic efficiency in leaves of M.micrantha associated with MMWV infection.