Ultrathin‐Film Titania Photocatalyst on Nanocavity for CO₂ Reduction with Boosted Catalytic Efficiencies

Abstract

Photocatalytic CO2 reduction with water to hydrocarbons represents a viable and sustainable process toward greenhouse gas reduction and fuel/chemical production. Development of more efficient catalysts is the key to mitigate the limits in photocatalytic processes. Here, a novel ultrathin‐film photocatalytic light absorber (UFPLA) with TiO2 films to design efficient photocatalytic CO2 conversion processes is created. The UFPLA structure conquers the intrinsic trade‐off between optical absorption and charge carrier extraction efficiency, that is, a solar absorber should be thick enough to absorb majority of the light allowable by its bandgap but thin enough to allow charge carrier extraction for reactions. The as‐obtained structures significantly improve TiO2 photocatalytic activity and selectivity to oxygenated hydrocarbons than the benchmark photocatalyst (Aeroxide P25). Remarkably, UFPLAs with 2‐nm‐thick TiO2 films result in hydrocarbon formation rates of 0.967 mmol g−1 h−1, corresponding to 1145 times higher activity than Aeroxide P25. This observation is confirmed by femtosecond transient absorption spectroscopic experiments where longer charge carrier lifetimes are recorded for the thinner films. The current work demonstrates a powerful strategy to control light absorption and catalysis in CO2 conversion and, therefore, creates new and transformative ways of converting solar energy and greenhouse gas to alcohol fuels/chemicals.

Strong Interference in Planar, Multilayer Perfect Absorbers: Achieving High-Operational Performances in Visible and Near-Infrared Regimes

“…As depicted in Figure 11(a)-(e), the asobtained structures significantly improve TiO2-photocatalytic activity and selectivity of oxygenated hydrocarbons more so than does the benchmark photocatalyst (Aeroxide P25). Remarkably, the MIS cavity results in hydrocarbon formation rates of 0.967 mmol , g h 1 1 -corresponding to 1,145-times higher activity than Aeroxide P25 [125].…”

Engineering approach toward catalyst design for solar photocatalytic CO 2 reduction: A critical review

“…For example, the photocatalytic CO 2 reduction efficiency of TiO 2 is highly dependent upon the particle size closely associated with the bandgap. Liu et al 90 chose the ultrathin TiO 2 film (<2 nm) as a typical example to investigate the light trapping mechanism for boosting solar‐driven CO 2 conversion efficiency. Figure 2C schematically demonstrates the unique ultrathin‐film catalytic system, namely a three‐layered reactor with TiO 2 as the light absorption film.…”

“…C, Schematic illustration of a three‐layered reactor with TiO 2 as the light absorption film. Reproduced with permission 89 . Copyright 2018, Wiley [Colour figure can be viewed at wileyonlinelibrary.com]…”

Hydrogen Sensing Using Thin-Film Perfect Light Absorber

“…The change in Pd nanograting complex refractive index red-shifted the absorption maximum Δλ max ≈ 19 nm and a change in the figure of merit (FOM ≡ Δ R / R ) of up to 500. On the other hand, realizing perfect light absorption using thin-film stack of metals, dielectrics, and semiconductors, has been demonstrated using different geometries. , Thin film light absorbers represent an inexpensive and scalable alternative that enables many applications, for example, structural coloring, solar thermal energy applications, , water splitting, photocatalysis, polarizers, and heat-assisted magnetic recording …”