Rice straw-based activated carbons doped with SiC for enhanced hydrogen adsorption

Abstract

Activated carbons (ACs) based on rice straw (RS) were synthesised using potassium carbonate as activating agent at three different K 2 CO 3 /RS weight ratios. Morphological, chemical, structural as well as textural characterisations were carried out in order to establish relationships between the physicochemical properties of the materials and their hydrogen adsorption capacities. The ACs contained potassium and silicon as the main impurities. Si was identified by XRD in both phases of silicon dioxide and silicon carbide. The presence of SiC was particularly surprising due to the rather low activation temperature, much lower than what is usually required for SiC synthesis. ACs exhibited well-developed surface areas (approximatively 2000e2100 m 2 g À1) and high micropore volumes, making them suitable for hydrogen storage applications. RS-based ACs showed higher hydrogen storage capacities than those previously obtained with KOH-activated sucrose. The latter exhibited hydrogen uptakes (excess, 10 MPa, 298 K) up to 0.55 wt. %, whereas 0.65 wt. % was measured for RSbased ACs in the same conditions. The higher hydrogen capacities and isosteric heats of adsorption found here were attributed to the presence of SiC.

Application of the modified Dubinin-Astakhov equation for a better understanding of high-pressure hydrogen adsorption on activated carbons

“…Q st,exc values between 4.5 and 9 kJ mol -1 were obtained. These values are in agreement with those obtained in our previous works [34,84], but are slightly higher than those commonly obtained for the adsorption of hydrogen on graphite [85][86][87]. Q st,exc was found to be almost constant in the range of n exc considered, which corresponds to a relatively low fractional filling.…”

Novel Porous Carbons Derived from Coal Tar Rejects: Assessment of the Role of Pore Texture in CO2 Capture under Realistic Postcombustion Operating Temperatures

“…The amount of adsorbed CO 2 per surface area (μmol.m -2 ) is presented in Figure 2d versus the average micropore size. This methodology and representation have been already used by several authors 55,56 . Representing the adsorbed CO 2 per surface area versus A BET and L 0 DR,N2 , a good fit was also obtained (R 2 = 0.86, Figure S3) but the quality of the fit was far better when using S NLDFT and L 0, NLDFT (i.e., R 2 = 0.93) (Figure 2d).…”

“…ACs are produced by physical or chemical activation of carbon precursors, which can be coals [11][12][13] , various pyrolized materials [14][15][16] , or biomass [17][18][19][20] . In any activation process, the ultimate goal is to increase the textural properties of the material (i.e., surface area and pore volume).…”

Review on a novel biosilica source for production of advanced silica‐based materials: Wheat husk

“…Owing to their special natural structure, while having silica as the main component, rice husk, rice straw, and wheat husk ash have the potential to be a starting material in the synthesis of silicon carbide and nitride ceramics. The preparation of SiC and SiC‐containing composites based on rice husk and rice straw is well known . However, there is only one report that explains the formation of SiC nanobelts, nanorods, nanotubes, and nanowires from wheat husk …”

“…The preparation of SiC and SiC-containing composites based on rice husk and rice straw is well known. 80 However, there is only one report that explains the formation of SiC nanobelts, nanorods, nanotubes, and nanowires from wheat husk. 79…”