Hydrogen Storage in Pristine and d10-Block Metal-Anchored Activated Carbon Made from Local Wastes

Abstract

Activated carbon has been synthesized from local palm shell, cardboard and plastics municipal waste in the Kingdom of Saudi Arabia. It exhibits a surface area of 930 m 2 /g and total pore volume of 0.42 cm 3 /g. This pristine activated carbon has been further anchored with nickel, palladium and platinum metal particles by ultrasound-assisted impregnation. Deposition of nanosized Pt particles as small as 3 nm has been achieved, while for Ni and Pd their size reaches 100 nm. The solid-gas hydrogenation properties of the pristine and metal-anchored activated carbon have been determined. The pristine material exhibits a reversible hydrogen storage capacity of 2.3 wt% at 77 K and 3 MPa which is higher than for the doped ones. In these materials, the spillover effect due to metal doping is of minor importance in enhancing the hydrogen uptake compared with the counter-effect of the additional mass of the metal particles and pore blocking on the carbon surface. OPEN ACCESS

Hydrogen Storage in Untreated/Ammonia-Treated and Transition Metal-Decorated (Pt, Pd, Ni, Rh, Ir and Ru) Activated Carbons

“…The steadiness of the micropore attributes, while improving the BET surface area for the ammonia-treated specimens, supports the assumption of the erosion effect of ammonia acting on mesopores and macropores, while the micropores were not affected due to their inaccessibility by the ammonia gas molecules [90,91]. On the other hand, platinum decoration had an opposite effect, owing to its additional metal mass and nanoparticle metal filling, as reported for deterioration upon metal decorations of activated carbons [28,101]. In addition, the average size of the decorated metal particles were in the range of meso/macropore sizes [102], implying that pore blocking would not affect the micropores, but might block only the mesopores and/or macropores, which would decrease the overall porosity and the surface area, as was reported [90].…”

“…Decoration of the graphitic surface with metals may improve the hydrogen adsorption by creating strong interaction sites. Furthermore, these metal centers can facilitate the dissociation of the hydrogen molecules to atomic hydrogen, and, subsequently, making them diffuse onto the graphitic skeleton through the spillover mechanism [28,48,[60][61][62][63][64][65][66]. However, the spillover effect was a dilemma for long time between theoretical and experimental studies due to hydrides formation [67][68][69][70], in addition to the inactivity of the metal surface due to clustering [71], hampering the spillover effect.…”

Influence of Catalytic Formulation and Operative Conditions on Coke Deposition over CeO2-SiO2 Based Catalysts for Ethanol Reforming

“…Consequently, partial reduction of the support must have occurred simultaneously to metal oxide reduction because of hydrogen spillover. The latter effect [44], in fact, promotes the migration of hydrogen atoms from the reduced metal particles (especially Rh and Pt) to the nearby ceria surface, thus assuring the reduction of lattice oxygen in the ceria surface, as well as bulk, along with the metal oxides [45]. In fact, the reduction of the Ce 4+ -O ions is shifted towards lower temperature range.…”

Local Pressure of Supercritical Adsorbed Hydrogen in Nanopores

“…However, hydrogen storage capacities at ambient temperatures are relatively low due to the weak binding energy. In fact, the heat of hydrogen adsorption in such materials is in the range of about 4–8 kJ/mol [10,11,12,13,14,15].…”