Composite of formamidinium lead bromide perovskite FAPbBr3 with reduced graphene oxide (rGO) for efficient H2 evolution from HBr splitting.

Solar hydrobromic acid (HBr) splitting using perovskite photocatalysts provides an attractive avenue to store solar energy into hydrogen (H2) and bromine (Br2), while an efficient photocatalytic system is still demanded. As for the semiconductor photocatalyst, formamidinium perovskites show some superiorities in structural stability, light adsorption and charge dynamics compared to their methylammonium counterparts, which are fitter for the photocatalysis process. Herein, the composite of formamidinium lead bromide perovskite (FAPbBr3) with reduced graphene oxide (rGO) is prepared using a facile photoreduction method. Under simulated sunlight irradiation (AM1.5G, 100 mW cm-2), this FAPbBr3/rGO composite (100 mg) demonstrates a noteworthy enhancement in photocatalytic H2 evolution activity of 386.7 µmol h-1, and it exhibits a notable stability with no significant decrease after 50 h of repeated tests. The single particle PL (photoluminescence) microscope is employed to study the charge dynamics, revealing that rGO in the composite effectively promotes the carrier separation. This work provides a highly efficient and stable photocatalyst for HBr splitting, and offers an effective modification strategy on lead bromide perovskites.

Lead-Free Perovskite Cs2 SnBr6 /rGO Composite for Photocatalytic Selective Oxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran.

Severe poisonousness and prolonged instability existing in organic-inorganic lead-based perovskite are two matters seriously hindering its potential future application in photocatalysis. Therefore, it is particularly important to explore ecology-friendly, air-stable and highly active metal-halide perovskites. Herein, a new and stable lead-free perovskite Cs2 SnBr6 decorated with reduced graphene oxide (rGO), is synthesized and employed in the photocatalytic organic conversion. The as-prepared Cs2 SnBr6 is ultrastable, exhibiting no clear changes after being placed in the air for six months. The Cs2 SnBr6 /rGO composite shows excellent photocatalytic activity in photo-driven-oxidation of 5-hydroxymethylfurfural (HMF) to high value enclosed 2,5-diformylfuran (DFF), achieving>99.5 % conversion of HMF and 88 % DFF selectivity in the presence of green oxidant O2 . Comprehensive characterizations disclose a multistep reaction mechanism, demonstrating that the molecular oxygen, photogenerated carriers, ⋅O2 - and 1 O2 altogether synergistically participate in the effective photo-driven conversion of HMF to DFF. This work expands the material gallery towards selective organic conversion and environmentally friendly perovskite options for photocatalytic application.

Alternatives to water oxidation in the photocatalytic water splitting reaction for solar hydrogen production.

The photocatalytic water splitting process to produce H2 is an attractive approach to meet energy demands while achieving carbon emission reduction targets. However, none of the current photocatalytic devices meets the criteria for practical sustainable H2 production due to their insufficient efficiency and the resulting high H2 cost. Economic viability may be achieved by simultaneously producing more valuable products than O2 or integrating with reforming processes of real waste streams, such as plastic and food waste. Research over the past decade has begun to investigate the possibility of replacing water oxidation with more kinetically and thermodynamically facile oxidation reactions. We summarize how various alternative photo-oxidation reactions can be combined with proton reduction in photocatalysis to achieve chemical valorization with concurrent H2 production. By examining the current advantages and challenges of these oxidation reactions, we intend to demonstrate that these technologies would contribute to providing H2 energy, while also producing high-value chemicals for a sustainable chemical industry and eliminating waste.

TGIN: Translation-Based Graph Inference Network for Few-Shot Relational Triplet Extraction.

Extracting relational triplets aims at detecting entity pairs and their semantic relations. Compared with pipeline models, joint models can reduce error propagation and achieve better performance. However, all of these models require large amounts of training data, therefore performing poorly on many long-tail relations in reality with insufficient data. In this article, we propose a novel end-to-end model, called TGIN, for few-shot triplet extraction. The core of TGIN is a multilayer heterogeneous graph with two types of nodes (entity node and relation node) and three types of edges (relation-entity edge, entity-entity edge, and relation-relation edge). On the one hand, this heterogeneous graph with entities and relations as nodes can intuitively extract relational triplets jointly, thereby reducing error propagation. On the other hand, it enables the triplet information of limited labeled data to interact better, thus maximizing the advantage of this information for few-shot triplet extraction. Moreover, we devise a graph aggregation and update method that utilizes translation algebraic operations to mine semantic features while retaining structure features between entities and relations, thereby improving the robustness of the TGIN in a few-shot setting. After updating the node and edge features through layers, TGIN propagates the label information from a few labeled examples to unlabeled examples, thus inferring triplets from these unlabeled examples. Extensive experiments on three reconstructed datasets demonstrate that TGIN can significantly improve the accuracy of triplet extraction by 2.34%  âˆ¼  10.74% compared with the state-of-the-art baselines. To the best of our knowledge, we are the first to introduce a heterogeneous graph for few-shot relational triplet extraction.

In Situ Preparation of CsPbBr3 @CsPb2 Br5 Composite Assisted with Water as a Highly Efficient and Stable Catalyst for Photothermal CO2 Hydrogenation.

Lead halide perovskite has triggered a lot of research due to its superior optical properties. However, halide perovskite materials have poor environmental stabilities and are easily affected by external factors such as water and heat, resulting in structural decomposition and performance failure. Contrary to this commonplace concept, it is found that CsPbBr3 (CPB) can convert to CsPb2 Br5 (CP2B5) partially when meeting a small amount of water, and the CsPbBr3 @CsPb2 Br5 (CPB@CP2B5) composite is synthesized by an in situ method accordingly. The CPB@CP2B5 composite shows an enhanced catalytic performance compared with pure CPB, as well as a dramatically synergistic effect of photo and thermal for catalytic CO2 hydrogenation. The CO production rate of CPB@CP2B5 is determined as 69 µmol g-1 h-1 under light irradiation at 200 °C, which is 156.8 and 43.4 times higher than that under pure photo (0.44 µmol g-1 h -1 ) and pure thermal (1.59 µmol g-1 h -1 ) condition, respectively. Meanwhile, the CPB@CP2B5 sample is also stable, which shows no significant decline in the catalytic activity during 8 cycles of repeated experiments. The probable mechanism is explored by utilizing a series of in situ characterizations.

Lead-Free Halide Perovskite Cs3 Bi2 x Sb2-2 x I9 (x ≈ 0.3) Possessing the Photocatalytic Activity for Hydrogen Evolution Comparable to that of (CH3 NH3 )PbI3.

Lead-free perovskites Cs3 Bi2 x Sb2-2 x I9 (x = 0.1, 0.3, 0.5, 0.7, 0.9) are prepared by a co-precipitation method and their photocatalytic performance for hydrogen production is studied in aqueous HI solution. Compared with the lead-based perovskite (CH3 NH3 )PbI3 , Cs3 Bi2 x Sb2-2 x I9 has a better catalytic performance under air mass 1.5 G (AM 1.5 G) simulated sunlight (100 mW cm-2 ), powders of Cs3 Bi0.6 Sb1.4 I9 (100 mg) loaded with Pt nanoparticles show < H2 evolution rate of 92.6 µmol h-1 , which greatly exceeds that of (CH3 NH3 )PbI3 powders loaded with Pt nanoparticles (100 mg catalyst, 4 µmol h-1 ). The Cs3 Bi2 x Sb2-2 x I9 has a high stability, with no apparent decrease in catalytic activity after five consecutive H2 evolution experiments. The doping of Sb in Cs3 Bi2 x Sb2-2 x I9 effectively reduces the contribution of Bi3+ on the conduction band, attenuating the effect of Bi vacancy on band structure. Compared with pure Cs3 Bi2 I9 and Cs3 Sb2 I9 , Cs3 Bi2 x Sb2-2 x I9 has fewer midgap states and better optical absorption, which greatly enhances its performance for the hydrogen evolution reaction.

Synthesis and Luminescence Properties of a Novel Yellow-White Emitting NaLa(MoO4)2: Dy3+, Li+ Phosphor.

Intense yellow-white NaLa(MoO4)2: Dy3+ phosphors co-doped with Li+ ions have been successfully synthesized via facile sol-gel combustion approach. The dependence of the crystal structure and crystallinity, particle morphology, photoluminescence property, fluorescent lifetime and absolute quantum efficiency of the as-prepared phosphors has been investigated. Stable yellow-white emission from 440 nm to 600 nm and higher absolute quantum efficiency were studied on Dy3+ doped NaLa(MoO4)2, Dy3+ and Li+ co-doped NaLa(MoO4)2, respectively. Surprisingly, only a small amount of Li+ can lead to a remarkable increase of the PL intensity and the quantum efficiency. Especially, along with 0.75 mol% Li+ ions induced in the NaLa(MoO4)2: Dy3+ phosphors, the absolute quantum efficiency increased from 13.8% to 22%, and the possible mechanism has been deeply discussed. Outstanding luminescence properties have certified that NaLa(MoO4)2: Dy3+, Li+ phosphors are promising candidates as new yellow-white components for optical devices.

Composite of CH3 NH3 PbI3 with Reduced Graphene Oxide as a Highly Efficient and Stable Visible-Light Photocatalyst for Hydrogen Evolution in Aqueous HI Solution.

A facile and efficient photoreduction method is employed to synthesize the composite of methylammonium lead iodide perovskite (MAPbI3 ) with reduced graphene oxide (rGO). This MAPbI3 /rGO composite is shown to be an outstanding visible-light photocatalyst for H2 evolution in aqueous HI solution saturated with MAPbI3 . Powder samples of MAPbI3 /rGO (100 mg) show a H2 evolution rate of 93.9 µmol h-1 , which is 67 times faster than that of pristine MAPbI3 , under 120 mW cm-2 visible-light (λ ≥ 420 nm) illumination, and the composite is highly stable showing no significant decrease in the catalytic activity after 200 h (i.e., 20 cycles) of repeated H2 evolution experiments. The electrochemiluminescence performance of MAPbI3 is investigated to explore the charge transfer process, to find that the photogenerated electrons in MAPbI3 are transferred to the rGO sites, where protons are reduced to H2 .

Optical-magnetic bifunctional properties and mechanistic insights on upconversion of NaYF4:Yb,Ho,Tm@NaGdF4 with a tunable nanodumbbell morphology.

The energy-upconversion of lanthanide-doped nanoparticles with a core-shell structure can be utilized to enhance and tune optical properties and can generate multifunctionality in a single system. Herein, the core-shell nanoparticles NaYF4:Yb,Ho,Tm@NaGdF4 were prepared by thermally decomposing lanthanide acetylacetonate precursors. Through modifying the molar ratio of the core and shell, nanodumbbell-shaped particles with different sizes and morphologies were precisely synthesized. The formation mechanism and the heterogeneous epitaxial growth process of the nanodumbbell-shaped particles were studied. After coating the shell layer, upconversion luminescence intensities, spectral purity and fluorescence lifetimes were improved. Furthermore, the magnetic performance of the core-shell nanoparticles was characterized. The optical-magnetic bifunctional upconversion core-shell particles with programmable shape and multiple properties provide an ideal platform for the preparation of nanodumbbell-shaped particles and the promotion of upconversion materials for biomedical research.