Criteria for Efficient Photocatalytic Water Splitting Revealed by Studying Carrier Dynamics in a Model Al‐doped SrTiO₃ Photocatalyst

Abstract

Overall water splitting (OWS) using semiconductor photocatalysts is a promising method for solar fuel production. Achieving a high quantum efficiency is one of the most important prerequisites for photocatalysts to realize high solar‐to‐fuel efficiency. In a recent study (Nature, 2020, 58, 411‐414), a quantum efficiency of almost 100% has been achieved in an aluminum‐doped strontium titanate (SrTiO3:Al) photocatalyst. Herein, using the SrTiO3:Al as a model photocatalyst, we reveal the criteria for efficient photocatalytic water splitting by investigating the carrier dynamics through a comprehensive photoluminescence study. It is found that the Al doping suppresses the generation of Ti3+ recombination centers in SrTiO3, the surface band bending facilitates charge separation, and the in‐situ photo‐deposited Rh/Cr2O3 and CoOOH co‐catalysts render efficient charge extraction. By suppressing photocarrier recombination and establishing a facile charge separation and extraction mechanism, high quantum efficiency can be achieved even on photocatalysts with a very short (sub‐ns) intrinsic photocarrier lifetime, challenging the belief that a long carrier lifetime is a fundamental requirement. Our findings could provide guidance on the design of OWS photocatalysts toward more efficient solar‐to‐fuel conversion.

Effect of dislocations on carrier recombination and photoelectrochemical activity in polished and unpolished TiO2 and SrTiO3 crystals

“…The peaks at 528.8 eV are associated with the O 2− ions in the crystal structure of SrTiO 3 , and the middle peak at around 531.4 eV is also correlated with higher oxygen vacancy concentrations of SrTiO 3 surface, [71][72][73] or a surface-absorbed hydroxyl group. [74][75][76] Furthermore, the peak intensity of the unpolished face at 528.8 eV is significantly lower than that of the polished face. It implies that the ratio of oxygen vacancies, which has a low formation energy, 77 or the hydroxyl on unpolished faces is higher than on polished faces.…”

Crystal Facet Engineering on SrTiO3 Enhances Photocatalytic Overall Water Splitting

“…Time-resolved photoluminescence (TR-PL) emission decay spectroscopy in Figure S30 reveals an almost unchanged average lifetime from 9.53 to 9.62 ns. Despite the exposed {111} facet of Cubo-STO does not significantly extend carrier lifetimes compared with cubic STO, the photocatalytic performance of OWS has still been substantially enhanced, indicating that the reactivity does not depend on prolonged carrier lifetimes . Instead, the highly efficient anisotropic charge separation and extraction mechanism between {100} and {111} facets plays a dominant role in the enhancement of photocatalytic OWS performance.…”

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.…”