Laser fragmentation of a high-entropy oxide for enhanced photocatalytic carbon dioxide (CO2) conversion and hydrogen (H2) production

Zahra Pourmand Tehrani, Theo Fromme, Sven Reichenberger, Bilal Gökce, Tatsumi Ishihara, Thomas Lippert, and Kaveh Edalati;

Abstract:

High entropy oxides (HEOs) have recently emerged as potential candidates for photocatalytic CO₂ conversion and H₂ production driven by their high structural stability and diversified elemental compositions. However, their practical use in photocatalysis is still limited particularly due to their comparatively small light absorbance and low active surface area. In this study, CO₂ conversion and H₂ production of an HEO TiZrHfNbTaO₁₁ photocatalysts, originally synthesized by high-pressure torsion (HPT), were enhanced by employing pulsed laser processing in water to effectively fragment micropowders to nanopowders. The process led to a 30 times larger active surface area and accordingly to enhanced light absorbance and higher photoelectrochemical performance for CO₂ and H₂O conversion. The generation of the large active surface area together with the formation of laser-induced crystal lattice defects not only enhanced the photocatalytic efficiency by at least one order of magnitude but also yielded CO, H₂ and CH₄ production even without requiring any additional co-catalyst. This study represents a notable step forward in developing active high-entropy photocatalysts by using new strategies such as laser fragmentation.