Stable anchoring of single rhodium atoms by indium in zeolite alkane dehydrogenation catalysts.

Maintaining the stability of single-atom catalysts in high-temperature reactions remains extremely challenging because of the migration of metal atoms under these conditions. We present a strategy for designing stable single-atom catalysts by harnessing a second metal to anchor the noble metal atom inside zeolite channels. A single-atom rhodium-indium cluster catalyst is formed inside zeolite silicalite-1 through in situ migration of indium during alkane dehydrogenation. This catalyst demonstrates exceptional stability against coke formation for 5500 hours in continuous pure propane dehydrogenation with 99% propylene selectivity and propane conversions close to the thermodynamic equilibrium value at 550°C. Our catalyst also operated stably at 600°C, offering propane conversions of >60% and propylene selectivity of >95%.

Reaction Mechanism and Selectivity Tuning of Propene Oxidation at the Electrochemical Interface.

Electrochemical conversion of propene is a promising technique for manufacturing commodity chemicals by using renewable electricity. To achieve this goal, we still need to develop high-performance electrocatalysts for propene electrooxidation, which highly relies on understanding the reaction mechanism at the molecular level. Although the propene oxidation mechanism has been well investigated at the solid/gas interface under thermocatalytic conditions, it still remains elusive at the solid/liquid interface under an electrochemical environment. Here, we report the mechanistic studies of propene electrooxidation on PdO/C and Pd/C catalysts, considering that the Pd-based catalyst is one of the most promising electrocatalytic systems. By electrochemical in situ attenuated total reflection Fourier transform infrared spectroscopy, a distinct reaction pathway was observed compared with conventional thermocatalysis, emphasizing that propene can be dehydrogenated at a potential higher than 0.80 V, and strongly adsorb via µ-C═CHCH3 and µ3-η2-C═CHCH3 configuration on PdO and Pd, respectively. The µ-C═CHCH3 is via bridge bonds on adjacent Pd and O atoms on PdO, and it can be further oxidized by directly taking surface oxygen from PdO, verified by the H218O isotope-edited experiment. A high surface oxygen content on PdO/C results in a 3 times higher turnover frequency than that on Pd/C for converting propene into propene glycol. This finding highlights the different reaction pathways under an electrochemical environment, which sheds light on designing next-generation electrocatalysts for propene electrooxidation.

High CO-Tolerant Ru-Based Catalysts by Constructing an Oxide Blocking Layer.

CO poisoning of Pt-group metal catalysts is a long-standing problem, particularly for hydrogen oxidation reaction in proton exchange membrane fuel cells. Here, we report a catalyst of Ru oxide-coated Ru supported on TiO2 (Ru@RuO2/TiO2), which can tolerate 1-3% CO, enhanced by about 2 orders of magnitude over the classic PtRu/C catalyst, for hydrogen electrooxidation in a rotating disk electrode test. This catalyst can work stably in 1% CO/H2 for 50 h. About 20% of active sites can survive even in a pure CO environment. The high CO tolerance is not via a traditional bifunctional mechanism, i.e., oxide promoting CO oxidation, but rather via hydrous metal oxide shell blocking CO adsorption. An ab initio molecular dynamics (AIMD) simulation indicates that water confined in grain boundaries of the Ru oxide layer and Ru surface can suppress the diffusion and adsorption of CO. This oxide blocking layer approach opens a promising avenue for the design of high CO-tolerant electrocatalysts for fuel cells.

A New Noncovalently Fused-Ring Electron Acceptor Based on 3,7-Dialkyloxybenzo[1,2-b:4,5-b']dithiophene for Low-Cost and High-Performance Organic Solar Cells.

The innovation of high-performance fused-ring electron acceptors (FREAs) has carried the field of organic solar cells (OSCs) toward a new stage of development. However, due to high synthetic complexity and production costs, FREAs may not be the most promising candidates for future commercialization applications. To address these disadvantages of FREAs, a series of low-cost acceptors, named as noncovalently FREAs (NFREAs), is successfully constructed by employing the strategy of noncovalently conformational locks. Herein, a novel NFREA (BDTO-4F) based on 3,7-dialkyloxybenzo[1,2-b:4,5-b']dithiophene is synthesized and fully characterized. Benefiting from the complementary absorption of the donor and acceptor, balanced charge transport, and favorable film morphology, J52:BDTO-4F based OSCs afford a satisfied power conversion efficiency of 12.09%, much higher than PBDB-T:BDTO-4F-based devices (8.30%). It is worth mentioning that BDTO-4F possesses a higher figure-of-merit value of 55.65 in comparison with several representative FREAs based on a cost-efficiency evaluation. This work demonstrates the potential of the novel benzo[1,2-b:4,5-b″]dithiophene derivative for constructing low-cost and high-performance NFREAs, providing a valuable insight on the materials design.

Chemoselective Hydrogenation of Nitroaromatics at the Nanoscale Iron(III)-OH-Platinum Interface.

Catalytic hydrogenation of nitroaromatics is an environment-benign strategy to produce industrially important aniline intermediates. Herein, we report that Fe(OH)x deposition on Pt nanocrystals to give Fe(OH)x /Pt, enables the selective hydrogenation of nitro groups into amino groups without hydrogenating other functional groups on the aromatic ring. The unique catalytic behavior is identified to be associated with the FeIII -OH-Pt interfaces. While H2 activation occurs on exposed Pt atoms to ensure the high activity, the high selectivity towards the production of substituted aniline originates from the FeIII -OH-Pt interfaces. In situ IR, X-ray photoelectron spectroscopy (XPS), and isotope effect studies reveal that the Fe3+ /Fe2+ redox couple facilitates the hydrodeoxygenation of the -NO2 group during hydrogenation catalysis. Benefitting from FeIII -OH-Pt interfaces, the Fe(OH)x /Pt catalysts exhibit high catalytic performance towards a broad range of substituted nitroarenes.