Crumpled reduced graphene oxide–amine–titanium dioxide nanocomposites for simultaneous carbon dioxide adsorption and photoreduction

Abstract

Crumpled reduced graphene oxide--amine--titanium dioxide nanocomposites (CGOATI) were synthesized by an one--step aerosol technique to enable simultaneous carbon dioxide (CO2) adsorption and photoreduction. Graphene oxide (GO), chemically modified by ethylenediamine (EDA), was crumpled using an aerosol process, encapsulating TiO2 nanoparticles to form core--shell nanostructures. The three--dimensional (3D) structure largely prevented the crumpled graphene nanosheets from restacking by minimizing π--π interactions, thus enhancing the stability of the catalyst by retaining its higher surface area. A combination of a 20% mass percentage of TiO2/GO, a 15:1 mass ratio of EDA/GO in precursor solution, and a 200 °C synthesis temperature led to the highest CO yield (65 µmol/g/h, with an apparent quantum efficiency of 0.0094%), which was two--fold higher than that of crumpled reduced GO--TiO2 (CGOTI) and four--fold higher than that of TiO2 alone. The enhancement of CO2 photoreduction was attributed to higher CO2 adsorption on the amine--functionalized reduced--GO (r--GO) surface and the strong electron trapping capability of r--GO. The insertion of EDA on r--GO nanosheets, the adsorption of CO2 by amine groups, and the photoreduction of the adsorbed CO2 were confirmed by FTIR and XPS spectra analysis. The r--GO nanosheets themselves were simultaneously photoreduced during CO2 photoreduction. Raman spectroscopy and conductivity measurements showed that photoreduced r--GO had a higher electronic conductivity than thermally reduced r--GO, and led to more effective CO2 photoreduction. This study offers new insights into the design and fabrication of graphene--based photocatalysts for CO2 photoreduction.

Delaminated CoAl‐Layered Double Hydroxide@TiO2 Heterojunction Nanocomposites for Photocatalytic Reduction of CO2

“…Apparent quantum efficiencies (AQE) for CO production over 3 wt% LDH-DS@TiO 2 -NT are around 0.26% and 0.09% under 365 nm (using a UV band pass filter) and 475 nm (visible band pass filter) irradiation (Table S4, Supporting Information), respectively. These AQEs are much higher than corresponding values of <0.1% (UV) for P25@ CoAl-LDH [27] or reduced graphene oxide-amine-titanium dioxide nanocomposites [49] or ZrOCo II −IrO x SBA-15 [50] wafer or Pt-TiO 2 [51] heterogeneous photocatalysts. They are also much greater than many "high performance" photocatalysts such as TiO 2 nanofibers (0.036%) [52] and SrNb 2 O 6 plates (0.065%) [51] under UV irradiation, and Co 3 O 4 hexagonal platelets under visible light [53] (0.069%, wherein a visible light sensitizer [Ru(bpy) 3 ]Cl 2 and hole scavenger triethanolamine (TEOA) were also required).…”

Catalysis of Carbon Dioxide Photoreduction on Nanosheets: Fundamentals and Challenges

“…[130] Surface functional groups (such as hydroxyl radicals,a mines) play an important role in the activity and selectivity of ar eaction. In this regard, amine functionalization favors the formation of alkylammonium carbamate, which converts into carbonate by hydrolysis [131] and possibly further to ac arboxyl radical. Such ar adical subsequently dissociates into CO under irradiation with UV light.…”

Katalyse der Kohlenstoffdioxid‐Photoreduktion an Nanoschichten: Grundlagen und Herausforderungen

“…[126] Allerdings kçnnen metalldotierte Photokatalysatoren während des Katalysezyklus zersetzt werden, was zu einer Auswaschung des dotierenden Metalls und einer stufenweisen Deaktivierung führt. In diesem Zusammenhang fçrdert eine Funktionalisierung durch Amine die Bildung von Alkylammoniumcarbamat, das über Hydrolyse zu Carbonat [131] und mçglicherweise weiter zu einem Carboxyl-Radikal reagiert. Bandkantenpositionen der MXene [120] und einschichtigen Metall-Phosphor-Trichalkogeniden (MPX 3 )b ezüglich der Potentialniveaus der CO 2 -Reduktion und Wasseroxidation.…”

“…[130] Funktionelle Oberflächengruppen (wie Hydroxyl-Radikale,Amine) spielen eine wichtige Rolle, wenn es um die Aktivitätund Selektivitätbei einer Reaktion geht. In diesem Zusammenhang fçrdert eine Funktionalisierung durch Amine die Bildung von Alkylammoniumcarbamat, das über Hydrolyse zu Carbonat [131] und mçglicherweise weiter zu einem Carboxyl-Radikal reagiert. Ein solches Radikal wird unter UV-Bestrahlung daraufhin zu CO dissoziiert.…”