Scanning curves of water adsorption on graphitized thermal carbon black and ordered mesoporous carbon

Abstract

Adsorption isotherms of water on porous carbons generally show large hysteresis loops whose origin is believed to be different from simple gases adsorption in mesoporous solids. In this paper, we discussed in details the behavior of water adsorption isotherms and their descending scanning curves for two carbons of different topologies, a highly graphitized thermal carbon black, Carbopack F, and a highly ordered mesoporous carbon, Hex. For both solids, very large hysteresis loops are observed, but their behaviors are different. For Carbopack F, the loop extends over a very wide range of pressure and the loop is larger when the descending is started from a higher loading; while for Hex, the hysteresis loop shows distinct steps, the number of which depends on the loading where the descending starts. By carefully analyzing the scanning curves from different loadings, we established the mechanism of water adsorption in Hex as a sequence of three steps: (1) water molecules adsorb on functional groups located at the junctions between adjacent basal planes of graphene layers, (2) growth of water clusters around the functional groups, and (3) bridging of adjacent clusters to form larger clusters, followed by a complete filling of mesopores.

A GCMC simulation and experimental study of krypton adsorption/desorption hysteresis on a graphite surface

“…This consists of polyhedral micro-particles with homogeneous graphene layers on the faces of the polyhedra. The characteristic properties of Carbopack F have been extensively reported elsewhere [17][18][19]. The BET surface area is 4.9 m 2 /g and there is no micropore or mesopore volume.…”

Advances in Porous Organic Polymers for Efficient Water Capture

“…The adsorption isotherms of porousc arbons with ap ore size of 1.1 nm show wide hysteresis loops and longer equilibrationt imes ranging from 5min to 16 h. The hydrophobic micropores of about 1nmi nw idth resulted in an indefinite adsorption hysteresis loop owing to the metastable structure formation of water molecules on the adsorptionb ranch.I mportantly,w ater molecules cannotf orm the metastable structures on the pore walls in cases where the sizes of the pores are less than the critical pore width of 0.6 nm, thus giving hysteresis-freea dsorption isotherms. Horikawa et al [36] studied the water adsorption hysteresis andt heir descending scanning curves on ah ighlyg raphitized thermal carbon black, Carbopack F, and ah ighly ordered mesoporous carbon,H ex, with hexagonals haped pores. The hysteresis loop of the water isotherm for Hex shows three steps:( 1) adsorption of water molecules onto the functional groups presented at the junctions between adjacent basal planes of graphene layers;( 2) water clusters grown aroundt he functional groups; and (3) formation of larger clusters by bridging of adjacent small water clusters, followed by complete pore filling of the mesopores.…”

Induced Potential in Porous Carbon Films through Water Vapor Absorption

“…Such sealing-and unsealing-induced voltage is completely repro-ducible (Figure 2a), thus indicating as trong correlation between the induced voltage and the relative humidity.T o scrutinize the quantitative relation between the voltage and RH value,wemeasured the steady-state voltage of the device at different humidities.A ss een in Figure 2b,t he voltage remains at zero at low humidity,starts to rise at 94 %RHand reaches am aximum when the humidity approaches saturation. [21] Based on the above observations,i tw as necessary to investigate how the induced voltage changes when the vapor condensation occurs.W e reduced the temperature of the PCF after saturated adsorption, and found that the induced voltage decreased dramatically when obvious condensation occurred ( Figure S6). [21] Based on the above observations,i tw as necessary to investigate how the induced voltage changes when the vapor condensation occurs.W e reduced the temperature of the PCF after saturated adsorption, and found that the induced voltage decreased dramatically when obvious condensation occurred ( Figure S6).…”