Silica‐Templated Continuous Mesoporous Carbon Films by a Spin‐Coating Technique

Abstract

Nanoporous carbon films and membranes are of importance for gas separations, membrane reactors, ultrafiltrations, sensors, fuel cells, and other applications.[1±5] Current synthesis methods such as chemical vapor deposition, [2] pulsed-laser deposition, [3] spray coating, [6] and ultrasonic deposition [7±9] techniques often result in microporous carbon thin films or membranes with average pore diameters of less than 1 nm. [4,6±10] Although microporous carbon thin films and membranes are effective for gas separation [6±9] and other applications, the small pore diameters may limit other applications that involve larger molecules. Incorporation of mesoporosity into nanoporous carbon thin films and membranes is therefore paramount in order to allow the transport of larger molecules and to enhance internal diffusion of the molecules. [1,10] Foley and co-workers [10] pioneered the synthesis of mesoporous carbon films by carbonizing the blends of poly (ethylene glycol) (PEG) and poly(furfuryl alcohol) (PFA).Removal of the PEG during the carbonization process resulted in mesoporous carbon thin films. This method allows the ready and efficient synthesis of mesoporous carbon thin films at low cost; however, it is still a challenge to achieve porous carbon thin films with high porosity, controllable pore size, and adequate pore accessibility. [10] This communication reports the synthesis of mesoporous carbon thin films by a rapid sol±gel spin-coating process, using low-cost sucrose and tetraethyl orthosilicate (TEOS) as precursors. As illustrated in Scheme 1, continuous sucrose/silica nanocomposite thin films are firstly formed by spin-coating homogenous sucrose± silicate±water solutions that are prepared by reacting TEOS in acidic sucrose-containing solutions. Carbonization converts the sucrose/silica thin films into carbon/silica nanocomposite thin films. Subsequent removal of the silica network using HF results in mesoporous carbon thin films with a uniform, interconnective pore network. Although nanoporous carbons have been synthesized using inorganic templates (e.g., zeolite and clays, [11±13] surfactant-templated mesoporous silica, [14±18] silica colloidal particles, [19±21] and sol±gel derivate silica frameworks [22±24] ), to the best of our knowledge, this is the first report of the synthesis of continuous mesoporous carbon thin films through a direct and rapid organic/inorganic self-assembly and carbonization process. Figure 1 shows the representative scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of the mesoporous carbon films after the removal of silica template, indicating the formation of continuous, smooth, and

Recent Progress in the Synthesis of Porous Carbon Materials

“…[43] Lu and his coworkers also reported the synthesis of continuous mesoporous carbon thin films by a rapid sol-gel, spin-coating process using sucrose as the carbon precursor and TEOS as the silica precursor. [44] Continuous sucrose/silica nanocomposite thin films were formed by the spin-coating of homogeneous sucrose/silicate/water solutions that were prepared by reacting TEOS in acidic sucrose solutions. Carbonization converted the sucrose/ silica thin films into carbon/silica nanocomposite thin films.…”

No More HF: Teflon‐Assisted Ultrafast Removal of Silica to Generate High‐Surface‐Area Mesostructured Carbon for Enhanced CO2 Capture and Supercapacitor Performance

“…[11] Furthermore,t he surface area of the ordered mesoporous carbon obtained through the hard-template method is very moderate in comparison to many high-surface-area disordered carbons. [12,13] Though as ilica-free strategy to prepare mesoporous carbon was reported as an alternate method, it involves usage of corrosive and expensive carbon precursors such as phenol and formaldehyde with ap olymeric template such as F127. [14] Furthermore,i ts uffers from significant amount of structural shrinkage during the carbonization process,r esulting in low surface areas,smaller pore sizes,and reduced pore volume.…”

Fabrication of continuous mesoporous carbon films with face-centered orthorhombic symmetry through a soft templating pathway

“…On the other hand, mesoporous carbon films have been prepared by spin coating of sucrose/silicate nanocomposite and subsequent removal of the silica. 23 However, the films obtained in this method show disordered pore systems.…”