Characterization of Interfacial Charge‐Transfer Photoexcitation of Polychromium‐Oxo‐Electrodeposited TiO₂ as an Earth‐Abundant Photoanode for Water Oxidation Driven by Visible Light

Abstract

Polychromium‐oxo‐deposited TiO2 (CrIIIxOy/TiO2) electrodes were fabricated by a simple electrochemical technique by using different TiO2 basal electrodes (anatase, rutile, and mixed polymorphic phases P25) as earth‐abundant photoanodes for visible‐light‐driven water oxidation. The high‐resolution transmission electron microscopy (HR‐TEM) observation illustrated that an CrIIIxOy layer with approximately 2–3 nm thickness was formed on the surface of the crystalline TiO2 particles. Upon visible‐light irradiation of the electrodes, the photoanodic current based on water oxidation was generated at the CrIIIxOy/TiO2 electrodes. However, the wavelength (below 620 nm) for photocurrent generation at CrIIIxOy/TiO2‐rutile was longer than that (below 560 nm) at CrIIIxOy/TiO2‐P25 by 60 nm, which is in agreement with the difference (0.2 eV) in the conduction band (CB) edge energy between rutile and anatase TiO2. This gives a quantitative account for the photocurrent generation based on interfacial charge transfer (IFCT) from Cr 3d of the deposited CrIIIxOy layer to the TiO2 CB. The photocurrent generated for CrIIIxOy/TiO2‐rutile was higher than that for CrIIIxOy/TiO2‐anatase, which is ascribed to 1) more effective CrIIIxOy deposition on the rutile particles, 2) a larger electrolyte/CrIIIxOy interface for water oxidation as a result of smaller rutile particles (ca. 30–40 nm) compared with larger P25 particles (ca. 40–80 nm), and 3) more effective use of visible light owing to the low energy IFCT transition of rutile.

Cocatalysts for Selective Photoreduction of CO2into Solar Fuels

“…In addition, the mechanism of IFCT (Figure D) is used to explain the photoexcitation by the incident photons with energy smaller than their corresponding band gap energies. So far, various clusters, such as CuS, , Cr x O y , Ag, Cu­(II), − and Fe­(III), − and chemical bonds have been proven to be good cocatalysts to carry out the photocatalytic O 2 reduction or H 2 evolution based on the IFCT mechanism. Clearly, these four mechanisms and their combinations are operational in photocatalysis over various kinds of the commonly used heterogeneous semiconductors.…”

A Simple Fabrication of Sb2S3/TiO2 Photo-Anode with Long Wavelength Visible Light Absorption for Efficient Photoelectrochemical Water Oxidation

“…Figure 2Ia shows the peaks of the ITO substrate. The diffracted peaks of TiO2/ITO (Figure 2Ib) and Sb2S3/TiO2/ITO electrodes (Figure 2Ic) were clearly detected at 2θ = 25.1°, 37.7°, 47.8°, 53.9° and 53.9°, respectively (JSPDF number: 89-4921) [5]. No peaks in terms of Sb2S3 were observed for both electrodes.…”

“…However, TiO 2 pAs-based PEC water oxidation is limited because of two serious drawbacks. First, TiO 2 has a wide bandgap (3.0-3.2 eV) that solely responds to the ultraviolet fraction of the solar spectrum (accounts for just 5% of solar irradiation) [5,6]. Second, a high recombination probability of electron-hole pairs leads to decreased incident light-to-current conversion efficiency.…”

Modulating surface charges of bismuth tantalum oxychloride nanoplates for promoting photogenerated charge separation

“…[7][8][9][10] Although progress has been made in photocatalytic water splitting, [11][12][13] it is unfortunate that numerous semiconductor-based photocatalysts still suffer the inherent limitation of fast electrons and hole recombination, leading to atrocious photocatalytic performance. [14][15][16] Modulating the behaviour of photogenerated charges on semiconductor photocatalysts through crystal facet engineering for exposing anisotropy facets has proven to be an effective strategy for promoting charge separation efficiency. [17][18][19][20][21][22] In addition, photocatalyst surface modication with suitable metal or metal oxide co-catalysts has also been widely recognized to accelerate the charge utilization process by fast extraction of photogenerated electrons and holes on the surface for photocatalytic reactions.…”

“…7–10 Although progress has been made in photocatalytic water splitting, 11–13 it is unfortunate that numerous semiconductor-based photocatalysts still suffer the inherent limitation of fast electrons and hole recombination, leading to atrocious photocatalytic performance. 14–16 Modulating the behaviour of photogenerated charges on semiconductor photocatalysts through crystal facet engineering for exposing anisotropy facets has proven to be an effective strategy for promoting charge separation efficiency. 17–22…”