Charge Separation Efficiency in WO₃/BiVO₄ Photoanodes with CoFe Prussian Blue Catalyst Studied by Wavelength‐Dependent Intensity‐Modulated Photocurrent Spectroscopy

Abstract

The understanding of charge carrier dynamics in complex heterojunctions is of the utmost importance for the performance optimization of photoelectrochemical cells, especially in operando. Intensity‐modulated photocurrent spectroscopy (IMPS) is a powerful tool to this aim, but the information content provided by this technique can be further enhanced by selectively probing each layer of complex heterojunctions by means of multiple excitation sources. Herein, the charge carrier dynamics of a WO3/BiVO4/CoFe–PB heterojunction, used in a conventional three electrode cell for water splitting, is studied using wavelength‐dependent IMPS (WD‐IMPS). The proposed data analysis allows us to identify the occurrence of interface recombination processes affecting the semiconductor junction, as well as the positive contribution of the inorganic complex catalyst on the charge separation efficiency of the BiVO4 layer. The deep understanding of the fate of charge carriers in the studied photoanode validates WD‐IMPS as a straightforward method to widen the understanding of such structures.

Improved Photoelectrochemical Performance of WO3/BiVO4 Heterojunction Photoanodes via WO3 Nanostructuring

“…This behavior is clearly ascribed to the BiVO 4 top layer in both heterojunctions and to its low efficiency in charge transfer to the solution. 54 On the other hand, the nanostructured WO 3 _NF-BV heterojunction electrode clearly exhibits a 6-fold higher charge separation efficiency compared to the planar WO 3 _P-BV heterojunction (Figure 6b), with η sep values of ∼10 and ∼60% at 1.23 V RHE for WO 3 _P-BV and WO 3 _NF-BV, respectively, which is consistent with the resistance values shown in Figure 4b and with the pinning of the bands shown by the capacitance (Figure 4c). Thus, the performance of the WO 3 _NF-BV electrode is much less limited by charge recombination in the bulk, in line with EIS results, which confirms the key role that morphology tuning has in the photogenerated charge transport properties of these materials.…”

Distribution of Relaxation Times Based on Lasso Regression: A Tool for High-Resolution Analysis of IMPS Data in Photoelectrochemical Systems

“…In the following, this simplified model will be called rate constant model (RCM), as previously introduced by Klotz et al With this approach, any insight into multistep or parallel charge transfer paths is hindered. As this typically occurs in heterostructured photoelectrodes and heterojunctions, some information can only be extracted by selectively probing each layer of the junction, as recently suggested by our group …”

“…As this typically occurs in heterostructured photoelectrodes and heterojunctions, some information can only be extracted by selectively probing each layer of the junction, as recently suggested by our group. 9 An IMPS experiment consists in measuring the frequencydependent photocurrent I ph (ω) produced by the system in response to a small light perturbation, usually expressed as a photon flux ϕ inc (ω), and then calculating the response function:…”

“…As this typically occurs in heterostructured photoelectrodes and heterojunctions, some information can only be extracted by selectively probing each layer of the junction, as recently suggested by our group. 9 …”

Self‐Assembled 2D/2D Schottky Heterojunction of Ti3C2/UiO‐66 Nanosheets for Boosting Photocatalytic H2 Evolution

“…How to convert it effectively to the other energy with appropriate routes, like hydrogen, has attracted intensive attention nowadays. A novel semiconductor, [1][2][3][4][5][6] metal-organic frameworks (MOFs), with unique characteristics of an organic-inorganic hybrid nature, [7,8] a large specific surface area, [9] abundant exposed active sites, [10] and tunable functionalities, [11] has been widely investigated in photocatalytic fields in the past decades, [12][13][14][15] including hydrogen evolution reaction (HER), [16][17][18] CO 2 reduction, [19,20] organic synthesis, [21,22] and degradation of organic pollutants. [23,24] The alternative components of MOFs endow the feature of an adjustable energy band structure that makes it have unparalleled advantages in photocatalytic HER, since it was firstly applied in 2009.…”