Entropy Oxides for Environmental Applications: HEO-Activated Carbon Composites for Photocatalysis

Abstract

High Entropy Oxides (HEOs) are a new class of materials with various unique characteristics that make them highly suitable for various applications. Their characteristics include thermodynamic stability, lattice distortions, and electronic properties, which make them suitable for applications like the photocatalytic remediation of environmental pollutants. The potential of rare earth-based high entropy oxide materials was theoretically and experimentally evaluated in this research project. In the second part of the research, synthesis of HEO-based activated carbon composite materials for photocatalytic remediation of organic pollutants was considered. Activated carbon produced using coconut shell biomass as feedstock and activated using phosphoric acid was used as a support medium for HEO nanoparticles. The structural properties of the HEO and its composites were studied using XRD, and the results unequivocally verified the presence of a single-phase pyrochlore-type entropy-stabilized material. In addition, the results of the UV-Vis Diffuse Reflectance Spectroscopy (DRS) analysis verified the presence of a direct bandgap of 2.16 eV with a very small width, indicating efficient visible light harvesting capability. Scanning electron microscopy and energydispersive spectroscopy were used to confirm that the HEO was uniformly dispersed in the activated carbon matrix. Raman spectroscopy confirmed the higher degree of short-range graphitic order in the AC700 support (ID/IG = 0.8343) relative to AC900 (ID/IG = 0.9632), and nitrogen adsorption analysis established a BET specific surface area of 502.97 m ), confirming the superiority of the optimized support. The photocatalytic activity of the HEO/AC was determined using Rhodamine B dye as a model compound under simulated solar light. It was determined that the optimized HEO/AC-2.8 had a removal efficiency of about 98.6%. This was due to the synergistic effect of adsorption and photocatalytic degradation. However, too much activated carbon was shown to hinder the photocatalytic efficiency due to the shielding effect of the activated carbon on the HEO nanoparticles. It was shown that the optimized HEO/AC maintained more than 92% of its activity even after reuse. It has shown that HEO materials can be used to improve the photocatalytic activity of activated carbon materials.