Efficient catalytic removal of COS and H_(2)S over graphitized 2D micro-meso-macroporous carbons endowed with ample nitrogen sites synthesized via mechanochemical carbonization

Developing a suitable catalyst for the elimination of highly toxic carbonyl sulfide(COS)and hydrogen sulfide(H_(2)S) is of great significance in terms of industrial safety and environmental protection.We demonstrate here the facile synthesis of graphitized 2D micro-meso-macroporous carbons by one-step carbonization of a mixture of urea and glucose at 700–900℃.The as-synthesized graphitized catalysts,designated as 2DNHPC-x(x=urea/glucose mass ratio),are endowed with an ultra-high concentration(12.9–20.2 wt%)of stable and versatile nitrogen sites(e.g.pyrrole and pyridine)which are anchored on the surface via stable covalent bonding.As a result,the 2D-NHPC-x are active in catalytic hydrolysis of COS on pyrrolic N to H_(2)S,and the H_(2)S can be subsequently captured on pyridinic N and converted to elemental sulfur at ambient conditions over the same materials.Among the prepared catalysts,2D-NHPC-x can catalytically hydrolysize 91%of COS to H_(2)S at 30℃,whereas the conversion ratio over the common catalysts g-C_(3)N_(4)and Fe_(2)O_(3)are below 6.0%.Furthermore,these catalysts also exhibit H_(2)S conversion and sulfur selectivity of nearly 100%at 180℃with long-time durability,which is higher than those of the most reported carbonbased catalysts.In contrast,the H_(2)S capacities of activated carbon,ordered mesoporous carbons(OMC)and N-doped OMC are 3.9,1.5 and2.39 mmol g^(-1),respectively.Both the experimental and theoretical results are disclosed that 2D-NHPC-x are superior to the nitrogen-doped porous materials ever applied in simultaneous catalytic elimination of both COS and H_(2)S.

基于高阶拓扑态的多维度声传输操控

高阶拓扑绝缘体展现出新奇的体-边对应关系,即d维n阶拓扑绝缘体具有(d-n)维拓扑保护的边界态.近年来,高阶拓扑绝缘体的相关物理概念已经被拓展到光子晶体、声子晶体等体系中.本文着重讨论声波高阶拓扑绝缘体的边界态在波调控中的具体应用.作者利用原胞的镜像对称性和滑移对称性,设计出一种拓扑非平庸的三维声子晶体.该声子晶体的体能带可由非平庸的量子化体极化表征,从而在不同维度的边界上存在拓扑保护的二维表面态、一维棱态、零维角态.作者对二维表面态和一维棱态加以利用,在实验上实现了拓扑边界态主导的声波在不同维度上的传播操控.具体来说,通过设计二维表面态的色散的设计,实现了声波的负折射;通过利用不同方向上的一维棱态传输,实现了三维里的声干涉.这些结果展示了高阶拓扑绝缘体在操控波传播方面具有独特的应用前景.