Origin of Enhanced Overall Water Splitting Efficiency in Aluminum‐Doped SrTiO₃ Photocatalyst

Abstract

With near unity quantum efficiency and operational stability surpassing 250 days in outdoor conditions, aluminum‐doped SrTiO3 (Al:SrTiO3) with tailored cocatalysts is one of the promising photocatalysts for scalable solar H2 production. Nevertheless, mechanistic insights behind Al‐doping and Rh cocatalyst‐induced enhanced overall water splitting (OWS) efficiency are not well elucidated. Herein, detailed charge carrier dynamics from sub‐picosecond to milliseconds are unveiled for Al:SrTiO3 by transient (optical and microwave probe) spectroscopy measurements. The obtained transients are rationalized using a theoretical model considering bimolecular recombination, trapping and detrapping processes. Due to a decrease in an n‐type doping density, Al doping of SrTiO3 significantly prolongs bulk carrier lifetime from 50 ns to 12.5 µs (consistent with the previous report). The crucial electron extraction process by the Rh cocatalyst located on the surface from Al:SrTiO3 occurs well before the decay of charge carriers. In contrast, µs‐long electron extraction time observed in SrTiO3 is significantly slower than tens of ns bulk carrier lifetime, thus reducing the photocatalytic OWS reaction. Complementary analysis in conjunction with in situ charge carrier dynamics in water interface addresses the mechanistic insight into Al‐doping‐induced enhancement of OWS activity. Correlating material properties, carrier dynamics and photocatalytic activity is expected to help design next‐generation photocatalysts via dopant and/or defects engineering for efficient solar‐fuel production.

Recent progress in defect‐engineered metal oxides for photocatalytic environmental remediation

“…SrTiO 3 is one of the ideal perovskite materials that have been extensively employed as a photocatalyst. 360,361 Recently, Cu-doped SrTiO 3 nanocubes (CuST) were synthesized in various proportions (Cu = 0.25, 0.5, 0.75. 1.00, 1.25 mol%) by Uma and coworkers for the photoreduction of Cr (VI) and degradation of methyl violet (MV) dye (Figure 14A).…”

Extending the Optical Absorption Limit of Graphitic Carbon Nitride Photocatalysts: A Review

“…While the photogeneration of charge carriers takes place in the bulk of the semiconductor, they must migrate to the surface of the semiconductor, which is the reaction site. Finally, interfacial electron and/or hole transfer results in reduction or oxidation reactions. − As a prerequisite, the conduction and valence bands of the photocatalyst must straddle with the reduction and oxidation potential of the target reaction. − The photocatalytic efficiency is collectively governed by the efficiency of light absorption, charge carrier generation, charge migration, and charge transfer across the semiconductor–electrolyte interface, as depicted in Figure .…”

An in situ study on the depth-resolved chemical states of undoped SrTiO3(001) surfaces during Ar+ sputtering and annealing processes with XPS

“…Recently, SrTiO 3 has also become the choice of future materials in the field of photocatalysts due to its high chemical stability under electrochemical potentials. 8–13 Correspondingly, many research studies have been conducted over the years for identifying the effective physical/chemical properties of SrTiO 3 that can be utilized for the practical applications of SrTiO 3 in the fields of electronics and chemical products.…”