Yang Jiang

Hydrogen evolution reaction (HER) from water through electrocatalysis using cost-effective materials to replace precious Pt catalysts holds great promise for clean energy technologies. In this work we developed a highly active and stable catalyst containing Co doped earth abundant iron pyrite FeS(2) nanosheets hybridized with carbon nanotubes (Fe(1-x)CoxS(2)/CNT hybrid catalysts) for HER in acidic solutions. The pyrite phase of Fe(1-x)CoxS(2)/CNT was characterized by powder X-ray diffraction and absorption spectroscopy. Electrochemical measurements showed a low overpotential of ∼0.12 V at 20 mA/cm(2), small Tafel slope of ∼46 mV/decade, and long-term durability over 40 h of HER operation using bulk quantities of Fe(0.9)Co(0.1)S(2)/CNT hybrid catalysts at high loadings (∼7 mg/cm(2)). Density functional theory calculation revealed that the origin of high catalytic activity stemmed from a large reduction of the kinetic energy barrier of H atom adsorption on FeS(2) surface upon Co doping in the iron pyrite structure. It is also found that the high HER catalytic activity of Fe(0.9)Co(0.1)S(2) hinges on the hybridization with CNTs to impart strong heteroatomic interactions between CNT and Fe(0.9)Co(0.1)S(2). This work produces the most active HER catalyst based on iron pyrite, suggesting a scalable, low cost, and highly efficient catalyst for hydrogen generation.

A series of low-bandgap polymers based on a soluble chromophore of 3,6-dithiophen-2-yl-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (DPP) unit were synthesized by introducing of different electron-rich building blocks copolymerized with DPP unit. Four new DPP-based polymers, PDPP-DTS, PDPP-F, PDPP-BDT, and PDPP-BDP, were characterized by GPC, TGA, NMR, UV−vis absorption, and electrochemical cyclic voltammetry. The results indicate that their bandgaps as well as their molecular energy levels are readily tuned by copolymerizing with different conjugated electron-donating units. In order to investigate their photovoltaic properties, polymer solar cell (PSC) devices based on PDPP-DTS, PDPP-F, PDPP-BDT, and PDPP-BDP were fabricated with a structure of ITO/PEDOT:PSS/polymers:PC70BM(1:2,w/w)/Ca/Al under the illumination of AM 1.5G, 100 mW/cm2. The power conversion efficiencies (PCE) of the four DPP-based PSC devices were measured and shown in this paper. The best performance of the PSC device was obtained by using PDPP-BDP as the electron donor material, and a PCE of 4.45% with an open-circuit voltage (Voc) of 0.72 V, a short-circuit current (Jsc) of 10.0 mA/cm2, and a fill factor (FF) of 61.8% was achieved, which is the best result among the DPP-based polymer materials. It is apparent that the PDPP-BDP-based device exhibits a very broad response range, covering from 300 to 850 nm. The results of the solar cells indicate that these types of materials are very promising candidates for highly efficient polymer solar cells.

Abstract Near‐infrared II (NIR‐II) imaging at 1100–1700 nm shows great promise for medical diagnosis related to blood vessels because it possesses deep penetration and high resolution in biological tissue. Unfortunately, currently available NIR‐II fluorophores exhibit slow excretion and low brightness, which prevents their potential medical applications. An atomic‐precision gold (Au) cluster with 25 gold atoms and 18 peptide ligands is presented. The Au 25 clusters show emission at 1100–1350 nm and the fluorescence quantum yield is significantly increased by metal‐atom doping. Bright gold clusters can penetrate deep tissue and can be applied in in vivo brain vessel imaging and tumor metastasis. Time‐resolved brain blood‐flow imaging shows significant differences between healthy and injured mice with different brain diseases in vivo. High‐resolution imaging of cancer metastasis allows for the identification of the primary tumor, blood vessel, and lymphatic metastasis. In addition, gold clusters with NIR‐II fluorescence are used to monitor high‐resolution imaging of kidney at a depth of 0.61 cm, and the quantitative measurement shows 86% of the gold clusters are cleared from body without any acute or long‐term toxicity at a dose of 100 mg kg −1 .