Mesoporous NiO Nanosheets for the Catalytic Conversion of Organic Contaminants

The increase in the global contamination of freshwater systems with industrial and natural chemical compounds is one of the key problems facing the world today. We report a simple fabrication strategy for hierarchical mesoporous NiO nanocrystals (NCs) with sheet-like morphologies using the hydrothermal method. This fabrication strategy introduces the controlled synthesis of scalable and high-yield mesoporous NiO nanosheets with high surface areas. The mesoporous NiO nanosheets were characterized by small- and wide-angle X-ray diffraction, nitrogen adsorption/desorption, scanning electron microscopy, and transmission electron microscopy. The as-prepared Ni(OH)2 sheets retained their hexagonal sheet morphologies during mild thermal treatment when converted to disordered mesoporous NiO NCs. The physical characteristics of the NiO nanosheets, such as intra-crystal mesoporosity, large surface area, and large pore volume, enabled phenolic pollutants such as o-aminothiophenol to access the active sites of the nanosheets. The NiO nanocatalyst with sheet-like morphology induced high catalytic efficiency and excellent reusability even after extended reutilization. In addition, the mechanistic pathway of phenolic pollutant transformation was demonstrated theoretically using density functional theory. The theoretical study provides insights into the changes in the molecular structure throughout the transformation mechanism of organic pollutants using the mesosporous NiO nanosheets.