Advances in engineering perovskite oxides for photochemical and photoelectrochemical water splitting

Abstract

Solar-driven water splitting is an efficient process for converting solar energy into chemical energy. In this process, semiconductor materials are excited by solar energy to generate free electrons to participate in the water-splitting reaction. Among these semiconductor materials, inorganic perovskite oxides have a spatial structure that is easy to control and thereby lead to different energy band structures and photocatalytic properties. More importantly, perovskite oxides can be compounded with other organic/inorganic materials to promote charge separation and improve apparent quantum yield. However, the low solar-to-hydrogen conversion efficiency has not yet reached the requirements of practical applications. In this review, the fundamental principles of solar-driven water splitting based on perovskite materials are introduced according to the most recently published results. In addition, the innovative modification techniques for water splitting based on perovskite oxides have been summarized, focusing on the following methods: element doping, homo/heterojunction formation, Z-scheme, plasmon effect, dye sensitization, carbon enhancement, and surface modifications. Note that the applications in the visible light wavelength range have been described, with emphasis among all these modification materials. Furthermore, the recent water-splitting reaction systems for practical applications are briefly discussed. As a summary, we outline the challenges and potential utilization associated with visible light–driven water splitting based on perovskite oxides for future commercial applications. This review describes various modification methods to improve photochemical performance of perovskite oxides as well as illustrates the potential to employ perovskite oxides as a key material for the practical application of water splitting.

Defects and Phase Formation in Non-Stoichiometric LaFeO3: a Combined Theoretical and Experimental Study

“…5,13 Recently, defect engineering has become a strongly emerging discipline in the context of perovskites, which aims at improving their catalytic performance by tailoring the stoichiometry and by incorporating defects at specific concentrations. 14,15 For example, due to charge compensation, the partial replacement of La 3+ by Sr 2+ in La 1−x Sr x FeO 3 leads to an increased concentration of both, Fe 4+ ions and oxygen vacancies, which enhance the activity of the catalytic reaction substantially. 16 Similarly, the charge state of Mn can be actively manipulated by replacing La 3+ with Ca 2+ in La 1−x Ca x MnO 3+δ , where the oxygen excess does not correspond to interstitial sites but is effectively realized by a complete oxygen lattice and cation vacancies.…”

Single-atom catalysts for high-efficiency photocatalytic and photoelectrochemical water splitting: distinctive roles, unique fabrication methods and specific design strategies

“…The changes in the electronic structure of g-C 3 N 4 aer the introduction of Pt SAs were examined by XPS and EXAFS. It was found that the XPS peaks assigned to p 2 -bonded N in N-containing aromatic rings (C-NC), sp 3 tertiary N (N-C 3 ), and amino functional groups (C-NH x ) shied to higher binding energy aer the loading of Pt SAs, indicating that the formation of Pt-N coordination bonds reduced the electron density of N atoms aer introducing Pt SAs. This phenomenon agreed well with the EXAFS results, which demonstrated the existence of Pt-N bonds in Pt SAs/g-C 3 N 4 .…”

“…Du et al's work highlights the importance of protecting active sites in the form of alloys and electronic structure modulation, which provides some new insights for the design of highly efficient SACs for solar water splitting. Ni SAs have also been successfully introduced as terminating agents to coordinate with sp 2 or sp 3 N atoms in heptazine units in polymeric carbon nitride (PCNNi) for efficient photocatalytic water splitting. 253 The hybridization of Ni SAs with N atoms in the heptazine ring in PCNNi led to the creation of new HOMO and LUMO states, contributing to the well-tuned band and electronic structures.…”

“…Photocatalytic and photoelectrochemical water splitting shows signicant potential for converting renewable solar energy to hydrogen (H 2 ) to allow access to largescale, practical, abundant and non-intermittent renewable energy supplies. [1][2][3][4][5][6][7] Reducing the kinetic barriers of the two half reactions, the H 2 evolution reaction (HER) and the oxygen evolution reaction (OER), in overall water splitting (OWS) can be achieved by tailoring the band and electronic structures and chemical properties of photo(electro)catalysts. Thus, the design and fabrication of high-performance photo(electro)catalysts played a core role in the achievement of high-efficiency photocatalytic and photoelectrochemical water splitting.…”

Revealing the role of surface elementary doping in photocatalysis

“…12 Doping semiconductors with foreign elements has been widely used to address the above issue. [13][14][15] This measure can modify the electronic states that influence the chemical activity of the semiconductor surface, [16][17][18] and the electronic processes including electron transport in the interior of the semiconductor and interfacial transfer of electrons to the cocatalysts. 19,20 Since the increase in the density of electronic states will undesirably prolong the detrapping time during electron transport and aggravate the charge leakage, 16,[21][22][23][24][25][26][27][28][29] it is desired to facilitate the rate-determining step in the forward reaction without exacerbating the detrimental effect by accurate elementary doping.…”