Aerogel was once hailed as a new material that changed the world. It has extremely broad application prospects in high-tech fields such as aerospace, national defense and civil fields such as construction and industrial pipeline insulation. From the structural point of view, aerogels are ultra-light porous nanomaterials assembled from low-dimensional nanostructures such as zero-dimensional quantum dots, one-dimensional nanowires or two-dimensional nanosheets through three-dimensional assembly. Various variables of low-dimensional nanostructures, such as geometry, size, density, surface morphology, chemical properties and other parameters, will have an important impact on the performance of the final aerogel obtained. So far, a variety of low-dimensional nanostructures have been assembled into aerogels with different functions, but the sizes of these nanostructured units are all below 100 nanometers, or even only a few nanometers. The challenge for the preparation of aerogels with structural units larger than 100 nanometers (ie sub-micron level) is huge, which is mainly caused by the following two reasons: 1. The larger the size of the aerogel structural unit, the greater the specific surface area. Small (the two are inversely proportional to each other). For sub-micron structural units, whether they are inorganic (higher density) or organic (lower density), the specific surface area of ​​the obtained aerogel is very small, thus losing the excellent aerogel's large specific surface area. Features; 2. Regardless of whether the connection between the nano-scale structural units is physical or chemical bonding, as the size of the structural unit becomes larger, the proportion of atoms in the connection to the total number of atoms will decrease sharply, so the assembled aerogel The material becomes brittle sharply as the size of the structural unit becomes larger.

    In response to this challenge, the aerogel team led by researcher Zhang Xuetong from the Suzhou Institute of Nanotechnology and Nanobionics, Chinese Academy of Sciences collaborated with Professor Song Wenhui of University College London and Professor Yan Lifeng of the University of Science and Technology of China to achieve an average diameter of 220 nanometers. Molecules (polyaniline polypyrrole copolymer) hollow spheres as the precursor, graphene oxide as the crosslinking agent, successively through the sol-gel process, supercritical fluid extraction process, high temperature heat treatment process and other key steps (as shown in Figure 1 ), successfully obtained a new type of all-carbon aerogel, that is, graphene cross-linked carbon hollow sphere aerogel (as shown in Figure 2). The presence of the crosslinking agent graphene ingeniously transforms the point-to-point contact between the ball and the ball into the point-to-surface contact, thus improving the mechanical properties of the final aerogel; the use of hollow sphere structure, and the use of sub-micron hollow sphere shell A large number of micropores are created in the layer to ensure that the final aerogel obtained has a large specific surface area; the selection of the precursor conductive polymer enables the final all-carbon aerogel to achieve nitrogen doping. The obtained graphene cross-linked carbon hollow sphere aerogel has low density ((51-67mg/cm3), high conductivity (263-695S/m), high specific surface area (569-609m2/g), high Young’s Many advantages such as modulus (1.8MPa) are expected to be widely used in energy (capture, storage, conversion), sensing, catalysis, adsorption, separation, functional composite materials and other fields. For example, carbon hollow spherical gas that crosslinks graphene Gel is used as an electrode material in a U-type thermoelectrochemical cell. The output power of the battery is as high as 1.05 W·m-2 (6.4 W·Kg-1), and its energy conversion efficiency relative to the Carnot cycle is as high as 1.4%. These values ​​are far Higher than the current value of the same type of device.

    This work provides a good design idea for the assembly of large-size particles into aerogels, and solves the technical problem of preparing functional aerogels from sub-micron structural units. The relevant results were published on Nano Energy (2017, 39, 470-477). Master students Dong Dapeng and Guo Haitao of the Suzhou Institute of Nanotechnology, Chinese Academy of Sciences are the co-first authors of the paper.

    These work were supported by the National Natural Science Foundation of China (51572285, 21373024), the Ministry of Science and Technology (2016YFA0203301) and the Suzhou Institute of Nanotechnology, Chinese Academy of Sciences.