Mixed atomic-scale electronic configuration as a strategy to avoid cocatalyst utilization in photocatalysis by high-entropy oxides

Abstract

To enhance the activity of photocatalysts for hydrogen production and CO2 conversion, noble metal cocatalysts as electron traps and/or acceptors such as platinum or gold are usually utilized. This study hypothesizes that mixing elements with heterogeneous electronic configurations and diverse electronegativities can provide both acceptor and donor sites of electrons to avoid using cocatalysts. This hypothesis was examined in high-entropy oxides (HEOs), which show high flexibility for atomic-scale compositional changes by keeping their single-or dual-phase structure. A new highentropy oxide was designed and synthesized by mixing elements with an empty d orbital (titanium, zirconium, niobium and tantalum) and a fully occupied d orbital (gallium). The oxide, synthesized by high-pressure torsion followed by calcination, had two phases (88 wt% orthorhombic (Pbcn) and 12 wt% monoclinic (I2/m)) with an overall composition of TiZrNbTaGaO10.5. It exhibited UV and visible light absorbance with a low bandgap of 2.5 eV, low radiative electron-hole recombination and oxygen vacancy generation due to mixed valences of cations. It successfully acted as a photocatalyst for CO and CH4 production from CO2 conversion and hydrogen production from water splitting without cocatalyst addition. These findings confirm that introducing heterogeneous electronic configurations and electronegativities can be considered as a design criterion to avoid the need to use cocatalysts.

References in corpus (4)

• Understanding the role of entropy in high entropy oxides
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• Understanding high photocatalytic activity of the TiO2 high-pressure columbite phase by experiments and first-principles calculations
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Cited by in corpus (6)

• Severe Plastic Deformation of Ceramics by High-Pressure Torsion: Review of Principles and Applications
• Photocatalytic Carbon Dioxide Methanation by High-Entropy Oxides: Significance of Work Function
• High-entropy perovskites as new photocatalysts for cocatalyst-free water splitting
• Active high-entropy photocatalyst designed by incorporating alkali metals to achieve d0+d10+s0 cationic configurations and wide electronegativity mismatch
• High-entropy oxide photocatalysts for green ammonia synthesis from nitrogen fixation in water
• Boosting hydrogen and methane formation on a high-entropy photocatalyst by integrating atomic d0/d10 electronic junctions and microscopic P/N heterojunctions