Morphological Engineering of Inorganic Semiconductor VIS-Light-Driven Nanocatalysts: Experimental and Theoretical Understandings

Abstract

Photocatalytic performances of inorganic semiconductors are mainly restrained by two factors: their low solar light harvesting capabilities and fast recombination of the generated charge carriers. Concerning the first point, some visible (VIS) light-driven catalysts, such as WO3 and metal halide perovskites (MHPs), have emerged during the past years as promising alternatives to traditional TiO2 based materials. Hole/electron pairs recombination, on the other hand, can be somehow controlled and slowed down via morphological engineering by rationally controlling the size and shape of the nanomaterial. In this work we discuss the recent breakthroughs achieved in the 2 photocatalytic applications of WO3 and MHP nanostructures, highlighting the intertwined role played by facet engineering and quantum confinement effects. State-of-art theoretical methodologies and tools available to model these systems and their operating mechanisms are presented and their strengths and limitations discussed. With this information we point to the main challenges that theory and experiments should jointly address to develop more efficient solar light driven catalyst technologies.

Visible-Light-Driven Toluene Oxidation to Benzaldehyde over WO3 Nanostructures

“…Several studies have reported that among various crystal structures of WO 3 , monoclinic (m-WO 3 ) (generated by annealing between 30 and 330 °C) is the most stable phase at room temperature. ,,,, Most often, exposed facets of (002) > (020) > (200) in the m-WO 3 with a distorted ReO 3 -type crystal structure result in rectangular sheet- and cubic-like nanoparticles. , Lin et al investigated the crystal facet effect of WO 3 nanowires and nanosheets in the photocatalytic oxidation of benzyl alcohol . They claimed that the WO 3 nanowires with the dominant exposed facet of {110} have a higher hole mobility than that of the WO 3 nanosheets with a {001} exposed facet, while the mobility of the electron on {110} is lower than that on {001}.…”

Hydration Mechanisms of Tungsten Trioxide Revealed by Water Adsorption Isotherms and First-Principles Molecular Dynamics Simulations

“…Given these appealing advantages as a standalone or combined photocatalyst in various heterojunctions, WO 3 has been the subject of many experimental − and theoretical studies − in recent years. In particular, the solid/liquid interfacial properties, crucial for the efficiency of photocatalytic processes, − have been theoretically investigated in the case of the WO 3 /water interface. ,, Previous computational studies have indeed addressed the fundamental understanding of the adsorption of water molecules on the γ-(001) surface [hereafter indicated as (001)]. ,,, Most of the reported studies have shown that water adsorbs preferentially in a molecular (undissociated) form since under-coordinated W atoms at the (001) surface are Lewis acids able to coordinate a water molecule …”

Effects of Size and Morphology on the Excited-State Properties of Nanoscale WO3 Materials from First-Principles Calculations: Implications for Optoelectronic Devices

“…To this end, theory has been proved to be a valuable tool to shed light on the photophysical phenomena underlying the charge generation and recombination processes in semiconductor NPs, once realistic structural models and a reliable methodology are finely set up. , In a previous work, we developed a combined GW -density functional theory (DFT) protocol to get an estimation of the energetic levels of realistic WO 3 NPs within a GW level of accuracy . We employed this methodology to draw important design rules to tune the energetic alignment in single WO 3 NPs and in WO 3 /WO 3 and WO 3 /TiO 2 NP heterojunctions based on the morphological engineering of the NP structures.…”