Research on the electrochemical degradation and hydrogen generation of Fraxinus mandshurica by polyoxometalate

The efficient utilization of wood waste is important for protecting the environment and solving the energy shortage problem. Taking Fraxinus mandshurica (FM) as an example, polyoxometalate (POM) was used as a catalyst for cyclic redox in an H-type electrolytic cell, where wood was oxidized to valuable small-molecule chemicals at the anode and hydrogen was generated at the cathode. The system successfully recycles energy, simultaneously converting biomass to chemical and electrical to hydrogen. Furthermore, the effects of various factors on the reaction were also investigated to obtain the optimal electrochemical conversion results for wood waste. At the optimal conditions, the FM degradation rate of 56.1%, with aromatic organic and carbonyl compounds as the main products, and the average Faraday efficiency of hydrogen generation can reach 93%, saving about 40% of energy consumption compared to water electrolysis at 0.1 A cm−2. Therefore, this electrochemical conversion method provides a new potential pathway for the application of wood waste.</p

Quinoxaline-Based Semiconducting Polymer Dots for in Vivo NIR-II Fluorescence Imaging

In vivo fluorescence imaging within the second near-infrared region (NIR-II, 1000–1700 nm) has advantages of a higher signal-to-background ratio (SBR), spatial resolution, and deeper tissue penetration depth than that in the visible (400–650 nm) and the first near-infrared window (NIR-I, 650–1000 nm). Here, we have synthesized three NIR-II fluorescent polymer dots (P1-Pdots, P2-Pdots, and P3-Pdots) for the NIR-II imaging. These Pdots were designed and optimized by using benzodithiophene as a donor unit and quinoxaline derivatives as acceptor units. The backbone and side chains of the quinoxaline acceptor units were varied to optimize the fluorescence performance. We found that the substituted position of alkoxy groups in the side chains plays an important role in enhancing the NIR-II window quantum yield (QY). In one case, the resulting nanoparticles (P1-Pdots) exhibited an emission peak at ∼1100 nm and a high QY of ∼1%. P1-Pdots possesses additional advantages for bioimaging, including deep tissue penetration depth, good stability, and biocompatibility. The blood vessel imaging of the mouse by P1-Pdots could be clearly observed with high spatial resolution and displayed an SBR of ∼2.1. Besides, P1-Pdots has further demonstrated its applications for tumor imaging of tumor-bearing nude mice, such as assessing the in vivo angiography and monitoring tumor vasculatures. Our results indicate the Pdots afford high fluorescence signals and spatial resolution for imaging deep tissues

Additive-Free All-Green Solvent-Processed Efficient and Stable Pseudo-Bilayer Bulk Heterojunction Ternary Organic Solar Cells

Most effective pseudo-bilayer planar heterojunction (PPHJ) devices, which facilitate vertical phase separation, often depend on toxic halogenated solvents in the production process. However, obtaining the desired morphology poses a significant challenge when utilizing nonhalogenated solvents due to the limitations of material solubility and unfavorable kinetics of film forming. The cooperative effect between the exciton dissociation and the exciton diffusion distance in PPHJ devices could be enhanced by accurate regulation of the donor: acceptor heterojunction. Hence, the pseudo-bilayer bulk heterojunction (PBHJ) strategy approach was used because of its process involving a dilute solution, aiming at optimizing phase formation kinetics and achieving a rational vertical components distribution in all-green o-xylene (o-XY) processed ternary organic solar cells (OSCs). In this study, a comprehensive analysis of charge recombination and carrier dynamics was conducted in three device structures: bulk heterojunction (BHJ), PPHJ, and PBHJ. It was found that the PBHJ device demonstrated enhanced charge generation, extended exciton lifetime, and reduced nongeminate charge recombination. Finally, the ternary PBHJ device based on PM6:BTP-eC9:L8-BO achieved a photovoltaic efficiency of 18.30%, significantly higher than those of the corresponding BHJ devices (17.38%). It is worth noting that the ternary PBHJ device exhibited excellent stability with 91.79% of the initial power conversion efficiency (PCE) retained after continuous illumination for 1 h under maximum power point (MPP) tracking, and the stability in the glovebox could still retain 92.55% of the initial PCE after 2700 h. This study provides valuable insights into optimizing the active layer phase separation and providing sufficient charge transport channels, thus improving the device stability

A Medium Bandgap D–A Copolymer Based on 4‑Alkyl-3,5-difluorophenyl Substituted Quinoxaline Unit for High Performance Solar Cells

Development of high-performance donor–acceptor (D–A) copolymers has been indicated as a promising strategy to improve the power conversion efficiencies (PCEs) of organic solar cells (OSCs). In this work, a new medium bandgap conjugated D–A copolymer, HFAQx-T, based on 4,8-bis­(5-(2-ethylhexyl)­thiophen-2-yl)­benzo­[1,2-<i>b</i>:4,5-<i>b</i>′]­dithiophene (BDT-T) as donor unit, 4-alkyl-3,5-difluorophenyl substituted quinoxaline (HFAQx) as the acceptor unit, and thiophene as the spacer, was designed and synthesized. HFAQx-T is a well-compatible donor polymer; OSCs based on HFAQx-T exhibit excellent performance in both fullerene and fullerene-free based devices. The optimized conventional single junction bulk heterojunction (BHJ) OSCs of HFAQx-T:PC₇₁BM showed a PCE of 9.2%, with an open circut voltage (<i>V</i>_oc) of 0.9 V, a short circuit current (<i>J</i>_sc) of 14.0 mA cm^–2, and a fill factor (FF) of 0.74. Also, when blended with 3,9-bis­(2-methylene-(3-(1,1-dicyano­methylene)­indanone)-5,5,11,11-tetrakis­(4-hexylphenyl)­dithieno­[2,3-<i>d</i>:2′,3′-<i>d</i>′]-<i>s</i>-indaceno­[1,2-<i>b</i>:5,6-<i>b</i>′]-dithiophene (ITIC), the HFAQx-T-based device exhibited a PCE of 9.6%. HFAQx-T is among a few D–A copolymers that can deliver >9% efficiency in both fullerene and fullerene-free solar cells. This work demonstrates that the 4-alkyl-3,5-difluorophenyl substituted quinoxaline (Qx) is a promising electron-accepting building block in constructing ideal D–A copolymers for OSCs