Continuous Oxygen Vacancy Gradient in TiO₂ Photoelectrodes by a Photoelectrochemical‐Driven “Self‐Purification” Process

Abstract

Oxygen vacancies have been treated as an important material engineering tool to enhance catalytic performance; for instance, oxygen vacancies suppress charge recombination at the Schottky interface, and thus, the photocurrent can be improved. In this regard, the gradient distribution of oxygen vacancies in n‐type metal oxides produces the ideal band structure for minimizing e−/h+ recombination by efficient hole extraction; however, its achievement remains a daunting challenge. Here, a photoelectrochemical (PEC)‐driven “self‐purification” process is suggested, which can effectively generate a gradient distribution of oxygen vacancies in the thickness range of ≈9.5 nm. As a result, a charge transport efficiency of >95% can be achieved by efficient hole migration from the photoanode to the electrolyte. This unique protocol is expected to provide an advanced metal oxide photocatalyst and photoelectrochemical electrode that exhibit superior photocatalytic performance with enhanced charge separation.

Modulating Co-catalyst/Facet Junction for Enhanced Photoelectrochemical Water Splitting

“…To understand how charge transfer was improved by the introduction of MNS, the injection and separation efficiency were calculated by measuring the photocurrent in the presence of methanol (Figure S18) and the theoretical photocurrent density. In principle, J p is governed by three factors: light absorption, charge separation, and charge injection following the equation where J abs is the photocurrent density converted from the absorbed photons, η sep is the yield of the photogenerated holes reaching the surface of a catalyst, and η inj is the yield of the surface-reaching holes that reacted with the electrolyte. , Assuming 100% internal quantum efficiency, the maximum achievable electron flux of the photoanodes could be reckoned by integrating the absorbance across the AM 1.5 solar spectrum (Figure S19). After integrating the electron flux within the wavelength range of 300–420 nm, J abs was determined to be 1.78 mA·cm –2 for pure TNR photoanodes.…”

“…where J abs is the photocurrent density converted from the absorbed photons, η sep is the yield of the photogenerated holes reaching the surface of a catalyst, and η inj is the yield of the surface-reaching holes that reacted with the electrolyte. 39,40 Assuming 100% internal quantum efficiency, the maximum achievable electron flux of the photoanodes could be reckoned by integrating the absorbance across the AM 1.5 solar spectrum (Figure S19). After integrating the electron flux within the wavelength range of 300−420 nm, J abs was determined to be 1.78 mA•cm −2 for pure TNR photoanodes.…”

Reconstructing Oxygen Vacancies in the Bulk and Nickel Oxyhydroxide Overlayer to Promote the Hematite Photoanode for Photoelectrochemical Water Oxidation

“…Since current research on improving the PEC-WS performance of α-Fe 2 O 3 -based photoanodes through this strategy is rather rare, the corresponding carrier-transport behavior is still unclear, and the real active site on the oxygen vacancies should be further studied. Therefore, it is imperative to explore the improvement of PEC-WS performance and the intrinsic mechanism for the α-Fe 2 O 3 photoanode with a catalytic overlayer after reconstructing oxygen vacancies. − …”

Synthesis of vacancy-rich titania particles suitable for the additive manufacturing of ceramics

“…Surface defects or vacancies can also modify the electronic levels 39 , optical absorption and emission properties and bring-in new roperties 40 . Oxygen vacancies present the lowest energy formation among the surface defects 41 which makes them ideal candidates to tailor the properties of oxide semiconductors such as TiO 2 42 .…”