TiO2/CoOx heterostructure decorated MIL-100(Fe) by atomic layer deposition for enhanced photocatalytic oxygen production

Abstract

Efficient separation of photogenerated charge carriers is essential for maximizing the photocatalytic efficiency of semiconductor materials in oxygen evolution reactions (OER). This study presents a novel trimetallic photocatalyst, MIL-100(Fe)/TiO₂/CoO_x, synthesized through a facile microwave-assisted hydrothermal method followed by atomic layer deposition (ALD). The porous MIL-100(Fe) serves as a support for the sequential deposition of TiO₂ and CoO_x layers via ALD, which enhances electron–hole pair separation and minimizes their recombination. Characterization using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) confirms the uniform deposition of TiO₂ and CoO_x layers on the MIL-100(Fe) surface. The optimized photocatalyst, processed with 20 deposition cycles of Co, exhibits exceptional photocatalytic OER performance, with an oxygen evolution rate of 558.3 μmol g⁻¹ h⁻¹. This enhancement in activity is attributed to the synergistic interaction between the spatially separated TiO₂ and CoO_x cocatalysts, which facilitates efficient charge transfer and increases the number of active sites. These findings highlight the potential of ALD-fabricated heterostructures in the development of advanced photocatalysts for sustainable energy production.