The efficient use of natural gas will require catalysts that can activate the first C-H bond of methane while suppressing complete dehydrogenation and avoiding overoxidation. We report that single iron sites embedded in a silica matrix enable direct, nonoxidative conversion of methane, exclusively to ethylene and aromatics. The reaction is initiated by catalytic generation of methyl radicals, followed by a series of gas-phase reactions. The absence of adjacent iron sites prevents catalytic C-C coupling, further oligomerization, and hence, coke deposition. At 1363 kelvin, methane conversion reached a maximum at 48.1% and ethylene selectivity peaked at 48.4%, whereas the total hydrocarbon selectivity exceeded 99%, representing an atom-economical transformation process of methane. The lattice-confined single iron sites delivered stable performance, with no deactivation observed during a 60-hour test.

Although considerable progress has been made in direct synthesis gas (syngas) conversion to light olefins (C2(=)-C4(=)) via Fischer-Tropsch synthesis (FTS), the wide product distribution remains a challenge, with a theoretical limit of only 58% for C2-C4 hydrocarbons. We present a process that reaches C2(=)-C4(=) selectivity as high as 80% and C2-C4 94% at carbon monoxide (CO) conversion of 17%. This is enabled by a bifunctional catalyst affording two types of active sites with complementary properties. The partially reduced oxide surface (ZnCrO(x)) activates CO and H2, and C-C coupling is subsequently manipulated within the confined acidic pores of zeolites. No obvious deactivation is observed within 110 hours. Furthermore, this composite catalyst and the process may allow use of coal- and biomass-derived syngas with a low H2/CO ratio.

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their simple device architecture, easy fabrication procedure, and low temperature processing. Many innovative approaches have been used to improve the performance of planar PSCs, such as PCE in 15.4% by dual-source vapor deposition technique, [ 5 ] 13.9% by a solvent-induced fast crystallization, [ 13 ] 13.1% by alkyl halide additives, [ 14 ] 15.1% by poly(3,4ethylene-dioxythiophene):polystyrenesulfo nate (PEDOT:PSS)-GeO 2 underlayer modifi cation, [ 15 ] 15.7% by cathode and anode dual modifi cations. [ 16 ] Despite the device effi ciency has achieved signifi cant progress, these perovskite solar cells have to be fabricated in very rigorous condition, i.e., in glove box with a humidity less than 1%. [ 17,18 ] To enable PSCs' commercial applications, one large challenge is to resolve the cell stability issue because the perovskite fi lms would be degraded gradually with time in air. [ 12,19 ] To date, a few studies have been focused on the processing circumstance and the stability issue of perovskite solar cells. You et al. [ 20 ] investigated the effect of humid environment on the thermal annealing of perovskite precursor fi lms. Bass et al. [ 21 ] reported that the moisture can prompt the crystallization of lead organohalide perovskites into the expected cubic phase. Yang et al. [ 22 ] demonstrated a fl exible PSC with a PCE of 7.14% which was fabricated under ambient. These studies suggest that the moisture plays an important role in the performance of perovskite solar cells. However, few studies focus on the mechanism how the moisture affects the cell degradation. In addition, controllable growth of the crystalline perovskite fi lms is regarded as the most important factor to obtain high-effi ciency PSCs. In general, the growth of crystalline perovskite fi lms is sensitively dependent on the solution concentration, precursor composition, solvent choice, deposition temperature, and so on. Crystallization controlling by manipulating the perovskite nucleation and growth can improve the fi lm morphology and coverage effectively. [ 22,23 ] Especially, solvent engineering plays very fascinating role in the controllable growth of solution-processed crystalline fi lms. Liang et al. reported that crystallization rate of perovskites could be controlled by incorporating 1,8-diiodooctane (DIO) additives into the precursor solution. [ 24 ] Song et al. demonstrated that perovskite crystallinity could be improved by introducing 1-chloronaphthalene (CN) additive in the perovskite precursor solution, which results in a 30% effi ciency improvement compared with the reference devices. [ 25 ] Most recently, Wu et al. obtained high quality PbI 2 fi lm with good coverage by A key issue for perovskite solar cells is the stability of perovskite materials due to moisture effects under ambient conditions, although their effi ciency is improved constantly. Herein, an improved CH 3 NH 3 PbI 3− x Cl x perovskite quality is demonstrated with good crystallization and stability by using water as an additive during crystal perovskite growt...

Mixed Pb-In perovskite solar cells are fabricated by using lead(II) chloride and indium(III) chloride with methylammonium iodide. A maximum power conversion efficiency as high as 17.55% is achieved owing to the high quality of perovskites with multiple ordered crystal orientations.

All-inorganic-based perovskites achieved by replacing the organic component with cesium (Cs) have drawn more attention because of their intrinsic inorganic stability. However, the cell efficiency in all-inorganic perovskite solar cells is still far below that in organic–inorganic hybrid perovskite-based devices. Here, we develop a new strategy to mediate the CsPbI2Br crystallization by directly doping copper­(II) bromide (CuBr2) into a perovskite precursor. The incorporation of CuBr2 played a role in retarding the crystallization dynamics process of CsPbI2Br film, resulting in a high-quality all-inorganic perovskite film with enlarged grain size, improved carrier mobilities, and reduced trap states. The fabricated perovskite solar cells delivered a champion power conversion efficiency of 16.15%, which is the highest efficiency in CsPbI2Br based all-inorganic perovskite solar cells and largely higher than 13.24% for pristine CsPbI2Br based device. The developed doping method paves a new route to fabricate high-performance all-inorganic perovskite solar cells.

PSS based device.

PSS) and CH3NH3PbIxCl3-x. In addition, perylene and perovskites form a fully crystalline heterojunction, which is beneficial for minimizing the defect and trap densities. Due to these merits, a maximum power conversion efficiency of 17.06% with improved cell stability is achieved. The finding in this work provides a simple route to control perovskite crystallizaition and to optimize the interfaces in PHJ PSCs simultaneously.