Pore-size control of soft mesoporous carbon by hot pressing

Abstract

As a facile post-synthesis approach for mesopore-size control of nanoporous carbon, we propose mechanical pressing of soft mesoporous carbons at 600 °C, namely hot pressing. Although conventional nanoporous carbons are mechanically hard and brittle, carbon mesosponge (CMS) which consists mainly of rarely stacked graphene walls is exceptionally soft, which is proved by its record small bulk modulus of 0.084 GPa. Thus, its mesopores with an average pore size of 7.36 nm can be further contracted by applying small mechanical pressures of only 10 MPa. Interestingly, the specific surface area and pore volumes of CMS increase on the application of relatively small mechanical pressure (< 20 MPa). This is ascribed to the exfoliation of weakly stacked graphene structures generated during the CMS synthesis process. Moreover, the average mesopore size of CMS can be finely tuned to the micropore scale as small as 2.14 nm under carefully adjusted mechanical pressure. Here we report the structural changes that occur upon hot-pressing focusing on the CMS crystallinity, graphene edge sites, and the framework flexibility. Although the CMS framework becomes harder on the application of mechanical force, CMS still retains its low bulk modulus, which is comparable to graphene mesosponge, known as a very soft carbon material. Thus, hot pressing of CMS provides a facile method to fabricate soft and elastic mesoporous carbons with controllable mesopore sizes between 2.14 to 7.36 nm.

Extraordinary Capacitance and Stability of Carbon Electrode for Electrochemical Capacitors

“…Furthermore, the nanostructures of GMS, particularly pore size, can be finely tuned over a broad range. 63 Thus, GMS is expected to be a nextgeneration electrode material for high-voltage electrochemical capacitors.…”

Progress in templated nanocarbons and related materials chemistry

“…GMS is characterized by developed mesoporosity (pore volume is 3-5 cm 3 g −1 ) [51], high surface area (1600-2000 m 2 g −1 ), high electric conductivity, high oxidation resistance [19], and remarkable mechanical elasticity [40]. CMS is significantly softer than GMS, and it is possible to reduce the initial pore size (approximately 7 nm) to around 2 nm by adjusting the mechanical pressure applied during the hot-pressing process [52].…”