Water glass (WG)-based aerogels (WAGs) are challenged with requirement of acid catalyst and poor mechanical property. In this work, we have developed a novel formamide (FA) as catalyst for gelation of WG at alkaline condition to prepare WAG monolith under atmospheric pressure drying (APD). The FA serves both as the catalyst by hydrolyzing product formic acid and drying control agent. The effect of the gelation temperature, FA dosage, and WG concentration on the gelation time, density, shrinkage and microstructure of the aerogels were analyzed. The optimum WAG monolith shows a low shrinkage of 20 % and density of 0.165 g cm −3 , as well as large specific surface area of 229.4 m 2 g −1 and superhydrophobic surface. The connected nanoparticle into three-dimensional network endows the WAG monolith with good mechanical property. Due to the low-cost, easy fabrication process and free usage of acids, the method expands the synthesis of aerogel monolith.
Qiuyan Shen,Weiren Chen,Zixuan Wei,Jing Tan,Min Wang,Yizhu Qiao,Lingxia Zhang,Jianlin Shi
Electrochemical C-N coupling reaction, transforming CO 2 and its derivatives (e.g., CH 3 OH, HCOOH) into highly-value-added organic nitrogenous compounds under ambient conditions, is considered as a promising way to reduce the current reliance of chemical production on fossil fuels. Herein, we synthesized CuO/In 2 O 3 hollow cubes for electrochemical synthesis of formamide from CH 3 OH and aqueous ammonia, achieving a Faradaic efficiency (FE) of formamide of as high as 49.05 % (43.06 ± 5.94 % on average), and a yield rate up to 8.43 ± 1.54 g h −1 mg cat −1 at a current density of 120 mA cm −2 , significantly higher than those of the reported catalysts. In-situ Raman spectra and theoretical calculations disclose that *CHO and *NH 2 intermediates are preferentially adsorbed on Cu and In sites, respectively. Electrons transfer between In and Cu via an In-O-Cu bridge, and the synergistic effects between In and Cu promotes the spontaneous coupling between *CHO and *NH 2 intermediates, thus facilitating the formation of C-N bond, and resulting in enhanced activity and selectivity in formamide synthesis. Using ethanol and propanol as C sources, acetamide and propionamide were obtained, respectively, demonstrating the generality of the as-synthesized catalyst. This work provides an effective strategy of constructing synergetic dual active sites to elevate the catalyst performance on amides electrosynthesis.
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