One-Step Excitation Overall Water Splitting over a Modified Mg-Doped BaTaO₂N Photocatalyst

Abstract

BaTaO 2 N responds to visible light up to 650 nm and exhibits photocatalytic activity during the hydrogen and oxygen evolution reactions. However, the difficulty in promoting both processes simultaneously hinders the realization of overall water splitting (OWS) over this material. Herein, we demonstrate the activation and stabilization of BaTaO 2 N−based photocatalysts for visible-light-driven OWS by combining flux-assisted nitridation with Mg doping and co-loading of Cr 2 O 3 /(Na)Rh and IrO 2 co-catalysts. RbCl-assisted nitridation produced single-crystal BaTaO 2 N particles doped with Mg and so promoted charge transfer to the co-catalysts. The coloading of Cr 2 O 3 /(Na)Rh and IrO 2 at moderate temperatures as co-catalysts to promote the hydrogen and oxygen evolution reactions, respectively, allowed the BaTaO 2 N photocatalyst to evolve hydrogen and oxygen simultaneously from water. This work highlights the importance of carefully tuning semiconducting and catalytic properties to realize effective charge transfer when preparing narrow-bandgap oxynitrides for OWS.

Sustainable photoanodes for water oxidation reactions: from metal-based to metal-free materials

“…98 The VB of metal nitride is determined by N 2p orbital, resulting in the potential generally insufficient for the water oxidation reaction. To improve the thermodynamics, one of the strategies is to achieve metal oxynitrides by the hybrid of N 2p orbital with O 2p orbital, and examples include LaTaO 2 N, SrTaO 2 N, and BaTaO 2 N. 99,100 Typically, BaTaO 2 N has presented a bandgap ca. 1.9 eV, which is even narrower than Ta 3 N 5 .…”

Overall Water Splitting by a SrTaO2N-Based Photocatalyst Decorated with an Ir-Promoted Ru-Based Cocatalyst

“…Obtaining an STH efficiency of 5%, which is the lowest value at which this process becomes practical, will require the development of the OWS photocatalysts having band gap energies, E g , below 2.1 eV . To date, InGaN-based nanorod arrays directly grown on a substrate have demonstrated STH of 3–5%. , However, only a few particulate photocatalysts, such as LaMg 1/3 Ta 2/3 O 2 N, , Ta 3 N 5 , Y 2 Ti 2 O 5 S 2 , and BaTaO 2 N, have been reported to have E g ≤ 2.1 eV and to drive OWS, and the apparent quantum yield (AQY) under visible light was at most 0.36% …”

“…1 To date, InGaN-based nanorod arrays directly grown on a substrate have demonstrated STH of 3−5%. 4,5 However, only a few particulate photocatalysts, such as LaMg 1/3 Ta 2/3 O 2 N, 6,7 Ta 3 N 5 , 8 Y 2 Ti 2 O 5 S 2 , 9 and BaTaO 2 N, 10 have been reported to have E g ≤ 2.1 eV and to drive OWS, and the apparent quantum yield (AQY) under visible light was at most 0.36%. 9 SrTaO 2 N (E g = 2.1 eV) is a perovskite-type oxynitride photocatalyst with a band structure suitable for promoting both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) from aqueous solutions under visible light.…”

“…Another crucial factor is the lack of cocatalysts to promote charge separation and simultaneous HER and OER. The dual cocatalyst strategy in which both a hydrogen evolution cocatalyst (HEC) and oxygen evolution cocatalyst (OEC) are incorporated into the OWS system has become popularly investigated to promote OWS effectively. ,, However, the possible HEC candidates are presently limited to certain noble metals . Bimetals and bimetallic oxides may provide enhanced activities compared with monometallic cocatalysts owing to the tunability of physicochemical properties. , Therefore, it would be desirable to explore the design of simple yet effective methods for synthesizing SrTaO 2 N with few defects and loading bimetallic metal or metal-oxide nanoparticles on photocatalyst surfaces jointly.…”

The development of an Ir and Sr-codoped KNbO3 photocatalyst as an O2-evolving photocatalyst for Z-schematic water splitting under visible light irradiation

“…Photocatalytic solar water splitting classified as artificial photosynthesis is a promising approach for the production of green hydrogen. 1,2 Not only the development of a single photocatalyst [3][4][5][6][7][8][9][10][11][12][13] but also the construction of a Z-scheme system employing two photocatalysts [14][15][16] has been extensively studied to realize highly efficient solar water splitting. Various photocatalysts can be employed as H 2 -and O 2 -evolving photocatalysts in the Z-scheme system.…”