Synergistic Effect of Metal–Organic Framework-Derived TiO₂ Nanoparticles and an Ultrathin Carbon Layer on Passivation of Hematite Surface States

Abstract

A passivation layer plays an important role in suppressing charge recombination on surface trap states. However, the effect of a single passivation layer is limited. Building a passivation system containing multiple passivation layers with different functions for efficient charge separation presents a challenge. In this study, we demonstrate the synergistic passivation effect between a metal−organic framework-derived TiO 2 nanoparticle layer and an ultrathin carbon layer, which facilitates the charge separation of an α-Fe 2 O 3 photoanode with a surface separation efficiency of 57%. The α-Fe 2 O 3 /TiO 2 /C photoanode generates a photocurrent of 1.93 mA cm −2 at 1.23 V vs a reversible hydrogen electrode, which is about 3.22 times higher than that of pristine α-Fe 2 O 3 . After the introduction of the cocatalyst β-FeOOH onto the α-Fe 2 O 3 /TiO 2 /C photoanode, a higher photocurrent of 2.95 mA cm −2 is generated under the same condition without doping and constructing a heterojunction.

Recent advances on interfacial engineering of hematite photoanodes for viable photo‐electrochemical water splitting

“…Liu et al demonstrated the synergistic passivation effect of multiple passivation layers consisting of a MOF‐derived TiO 2 nanoparticle layer and an ultrathin carbon layer(Figure 12(D)). 104 The complex photoanode yielded a photocurrent of 1.93 mA cm −2 at 1.23 V RHE . Further decorating the complex photoanode with β‐FeOOH cocatalyst, exhibiting a higher photocurrent of 2.95 mA cm −2 .…”

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“…(D) Schematic illustration of FeOOH/TiO 2 /C/Fe 2 O 3 (F/T/C/FH) complex photoanode for PEC water splitting (ss: surface trap states). Source: Reprinted with permission from Reference 104 copyright (2020) American Chemical Society…”

Semiconductor‐based Photoanodes Modified with Metal‐Organic Frameworks and Molecular Catalysts as Cocatalysts for Enhanced Photoelectrochemical Water Oxidation Reaction

“…To suppress the charge recombination on the surface of Fe 2 O 3 photoanode, the MOF‐derived TiO 2 nanoparticles layer and ultrathin carbon layer were synthesized by Wu et al. through hydrothermal method followed by calcination and immersion in glucose solution followed by calcination process [94] . The α‐Fe 2 O 3 /TiO 2 /C photoanode shows a photocurrent density of 1.93 mA ⋅ cm −2 at 1.23 V RHE , which is about 3.22 higher than that of bare α‐Fe 2 O 3 photoanode.…”

Modification of Ti‐doped Hematite Photoanode with Quasi‐molecular Cocatalyst: A Comparison of Improvement Mechanism Between Non‐noble and Noble Metals

“…[24] Among a large amount of cocatalyst species, molecular catalysts emerged in recent years on account of their many advantages: (i) clear structure, active site, and catalytic mechanism; (ii) tunability; (iii) direct improvement of the intrinsic activity; and (iv) metal-atom economy. [6,25] Metalorganic frameworks (MOFs), both preserving their original molecular structures [26,27] and being converted into inorganic metallic compounds, [28,29] are the main materials that have been developed as cocatalysts. For some other molecular catalysts possessing fast OER kinetics, they have great potential to be developed as cocatalysts of the photoanodes for PEC water splitting.…”