No abstract

Owing to their outstanding effect on improving catalytic reactivity, alkali-metal promoters have been widely used in industry [1,2] and extensively studied in academia. [3][4][5][6][7][8][9][10][11][12] Potassium-promoted iron catalysts for Fischer-Tropsch synthesis (FTS) and ammonia synthesis are the most representative examples of this effect. Owing to the complexity of real catalytic systems, the microscopic understanding of the alkalimetal promotion effect is still an elusive and challenging subject.In the past decades, most experimental and theoretical studies have focused on the co-adsorption systems involving alkali-metal atoms, for example, K + CO/metal. Five types of alkali-metal-adsorbate interactions were proposed to explain the alkali-metal promotion effect: 1) substrate-mediated charge transfers, [3] 2) direct bonding between alkali metal and adsorbate, [4] 3) electrostatic interactions, [5] 4) alkalimetal-induced molecular polarization, [6] and 5) nonlocal alkali-metal-induced enhancement of the surface electronic polarizability. [7] Although these studies represent excellent surface science, they are not immediately relevant to catalysis, because alkali-metal salts (or oxides) rather than metallic alkalis are used in heterogeneous catalysis. More importantly, previous studies only highlighted the alkali-metal-induced effect on the electronic structure of metallic substrate and coadsorbed molecules, while the more intriguing aspect, the alkali-metal effect on the surface structure of catalysts, has never been taken into account. On the basis of these proposals, the drastic changes in catalytic activity and selectivity caused by very low loadings of alkali-metal promoters cannot be reasonably explained. [8] As metallic iron is the active catalyst in ammonia synthesis, [9] iron-based FTS catalysts show an rich phase chemistry of metal, oxides, and carbides under reaction conditions.

No abstract

No abstract

No abstract

No abstract

A low‐temperature solution‐processed strategy is critical for cost‐effective manufacture of flexible perovskite solar cells (PSCs). Based on an aqueous‐processed TiO2 layer, and conventional fullerene derivatives replaced by a pristine fullerene interlayer of C60, herein a facile interface engineering for making all‐solution‐processed TiO2/C60 layers in flexible n‐i‐p PSCs is reported. Due to the improvement of the perovskite grain quality, promotion of interfacial charge transfer and suppression of interfacial charge recombination, the stabilized power conversion efficiency for the flexible PSCs reaches as high as 16% with high bending resistance retention (≈80% after 1500 cycles) and high light‐soaking retention (≈100% after 100 min). In addition, the stabilized efficiency is over 19% for the rigid TiO2/C60‐based PSCs. The present work with the facile low‐temperature solution process renders the practicability for high‐performance flexible PSCs applied to wearable devices, portable equipment, and electric vehicles.

No abstract