Hybrid Photo- and Thermal Catalyst System for Continuous CO₂ Reduction

Abstract

Heterogeneous thermal catalytic processes are vital for industrial production of fuels, fertilizers, and other chemicals necessary for sustaining human life. However, these processes are highly energy-intensive, requiring a vast consumption of fossil fuels. An emerging class of heterogeneous catalysts that are thermally driven but also exhibit a photochemically enhanced rate can potentially reduce process energy intensity by partially substituting conventional heat (where fossil fuels are needed) with solar energy. Such catalyst systems have yet to be practically utilized. Here, we demonstrate a compact electrically heated photo-and thermal annular reactor module to reduce CO 2 to CO, via the reverse water gas shift reaction. A first-principles-based design approach was taken in developing a SiO 2 on an Al photo-and thermal catalyst system for the model photo-and thermal indium oxide hydroxide (In 2 O 3−x (OH) y ) catalysts. A 5-fold light enhancement in the CO production rate and over 70 h of stable CO production were achieved. This represents the highest light enhancement effect reported for this model photocatalyst to date. The reactor presented herein allows continuous operation and a significant reduction of 31% in heater power consumption when provided with an additional 2 suns of irradiation, demonstrating the strong photo-and thermalharvesting performances of the catalyst system developed in this work.

The Importance of the Macroscopic Geometry in Gas‐Phase Photocatalysis

“…[89] If the substrate is thermally conductive, then also heat energy can be supplied to the photocatalyst to drive a photothermal reaction. [90] In contrast to all the examples discussed so far in Section 6, we now turn to nanoparticle-based aerogels as macroscopic photocatalysts that are completely self-supporting, i.e., there is no 3D support that dictates the geometry of the photocatalyst. This has the great advantage that no material other than the photocatalyst absorbs the light, and much higher catalyst loadings per volume [88] Copyright 2018, American Chemical Society.…”

“…[ 89 ] If the substrate is thermally conductive, then also heat energy can be supplied to the photocatalyst to drive a photothermal reaction. [ 90 ]…”

Thermo-photo catalysis: a whole greater than the sum of its parts

“…Furthermore, the power required to shine the light is lower than that required to heat the reactor, so the overall energy consumption can be reduced by introducing photo energy and lowering thermal input for thermal catalytic systems. 34,73,74…”

Shedding light on CO2: Catalytic synthesis of solar methanol

“…Although the photocatalytic efficiency of CO 2 reduction into methanol has been improved a lot, the low solar‐to‐fuel efficiency for industrialization is still the major obstacle 41‐43 . Therefore, to achieve better catalytic performance, different strategies have been proposed, including the combination of electrochemical process or/and the thermochemical process with photocatalytic process 6,14,44‐49 …”