Nanoscale Effects in Water Splitting Photocatalysis

Abstract

From a conceptual standpoint, the water photoelectrolysis reaction is the simplest way to convert solar energy into fuel. It is widely believed that nanostructured photocatalysts can improve the efficiency of the process and lower the costs. Indeed, nanostructured light absorbers have several advantages over traditional materials. This includes shorter charge transport pathways and larger redox active surface areas. It is also possible to adjust the energetics of small particles via the quantum size effect or with adsorbed ions. At the same time, nanostructured absorbers have significant disadvantages over conventional ones. The larger surface area promotes defect recombination and reduces the photovoltage that can be drawn from the absorber. The smaller size of the particles also makes electron-hole separation more difficult to achieve. This chapter discusses these issues using selected examples from the literature and from the laboratory of the author.

Probing of coupling effect induced plasmonic charge accumulation for water oxidation

“…6) [ 28 , 32 ], its sign is also sensitive to the direction of charge transfer, i.e. the type of photogenerated majority charge accumulated on the surface [ 33 ]. To rule out the possible contribution from plasmonic photothermal effects (details in Supplementary data), the light intensity used in the KPFM experiments was maintained at a moderate level (0.5 mW/cm 2 ) in KPFM experiments guaranteeing Au dimer's stabilization.…”

A Review of Photoelectrocatalytic Reactors for Water and Wastewater Treatment

“…To avoid this problem, immobilising the photocatalyst onto a substrate has been studied [23]; however, immobilisation reduces the specific surface area in contact with the solution and introduces a mass transport problem to the system, meaning immobilised systems are typically less effective than suspension systems [24]. Photocatalytic materials may also exhibit short electron-hole lifetimes (i.e., fast recombination) and low mobility, in which the diffusion length of the electron is normally larger than the diffusion length of the hole [25]. Therefore, the application of an external electrical bias in PECs can be used to overcome these problems.…”

Understanding the Structural and Electronic Properties of Photoactive Tungsten Oxide Nanoparticles from Density Functional Theory and GW Approaches

“…At this size the effects of the quantum confinement facilitate the transfer of charge carriers. 3,4 This implies that the size and morphology of NPs are two important factors in determining their electronic structure and, hence, their potential use as photocatalysts. 5 The effect of the structural features can be phenomenologically observed by experiments but a deep understanding, and more importantly, a systematic rationalization of the structure-property relationships is not straightforward and requires relying on large-scale atomistic simulations based on accurate theoretical methods and realistic structural models.…”