Hydrogen Production through Glycerol Photoreforming on TiO2/Mesoporous Carbon: Influence of the Synthetic Method

Abstract

This article explores the effect of the synthetic method of titanium dioxide (TiO2)/C composites (physical mixture and the water-assisted/unassisted sol-gel method) on their photocatalytic activity for hydrogen production through glycerol photoreforming. The article demonstrates that, apart from a high surface area of carbon and the previous activation of its surface to favor titania incorporation, the appropriate control of titania formation is crucial. In this sense, even though the amount of incorporated titania was limited by the saturation of carbon surface groups (in our case, ca. 10 wt.% TiO2), the sol-gel process without water addition seemed to be the best method, ensuring the formation of small homogeneously-distributed anatase crystals on mesoporous carbon. In this way, a ca. 110-fold increase in catalyst activity compared to Evonik P25 (expressed as hydrogen micromole per grams of titania) was achieved.

Sustainable Hydrothermal and Solvothermal Synthesis of Advanced Carbon Materials in Multidimensional Applications: A Review

“…For example, Escamilla et al (2020) presented significantly reduced calcination times for the preparation mesoporous carbon-supported TiO 2 (TiO 2 /MC, to 2 h at 400 • C). As such, this method not only benefited from lower reaction temperatures, but decreased reaction times and the resulting TiO 2 /MC possessed enhanced textural properties [48]. On the other hand, conventional arc-discharge is widely reported for its high-power consumption as the reactions are conducted under high temperatures.…”

“…There are some methods that exist in the literature that utilise low temperatures and shortened thermal treatment times. One such study was conducted by per Escamilla et al (2020) where calcination times were reduced to just 2 h. However, further research into such reactions need to be conducted [48]. This can be achieved through combinatorial approaches such as MWA-sol-gel-synthesis.…”

“…In addition to multidoping, other developments in manipulating reactants in sol-gel approaches have been reported. One example of such was presented by Escamilla et al (2020). The authors eliminated water from the reaction during the precursor mixing step.…”

“…Highly ordered TiO 2 /MC structures were produced, which enhanced catalytic properties during hydrogen production. The notable advantages of this method, together with many sol-gel approaches with calcination/carbonisation steps, are the lower temperatures (400 • C) used [48]. The latter feat may encourage the future adoption of such methods, further made attractive by the shorter reaction times (2 h) that sufficed the larger formation of the desired anatase phase.…”

“…Some of these would be the synthesis of GO using conventional methods followed by MWA exfoliation. To this effect, Voiry et al (2016) reported 100% yields of highly ordered, single-layer reduced graphene oxide (rGO) from MWA-HTC [48]. Herein, the approach was a simple one in that the GO obtained using the Modified Hummers' method, was coagulated by a stream of a CaCl 2 solution into the reaction vessel in the presence of argon.…”