Improved photocatalytic activity of novel NiAl₂O₄/g-C₃N₄ binary composite for photodegradation of 2,4-dinitrophenol and CO₂ reduction via gas phase adsorption

Immense interest has been expressed in the efficient conversion of solar to chemical energy using promising semiconductor-based photocatalysts, seen as a prospective solution for energy problems and environmental remediation. In particular, employing photocatalytic technology to reduce CO₂ into carbon fuels and degrade 2,4-dinitrophenol has become a much-discussed topic in renewable energy. In this study, binary NiAl₂O₄/g-C₃N₄ (NAO/g-CN) composites were synthesized via a process of calcination followed by sonication, which enhanced the transfer of photogenerated electrons from g-C₃N₄ to NiAl₂O₄, creating a much greater excited reductive electron charge on the surface of NiAl₂O₄. The crystallographic, electron-microscopy, photoemission spectroscopy, electrochemical and spectroscopic characterizations of the prepared composites allowed insights into their photocatalytic activity in the photoreduction of CO₂ and photodegradation of 2,4-dinitrophenol (2,4-DNP). The most active photocatalyst, 40% NAO/g-CN, produced 10.73 μmol g⁻¹h⁻¹ of CO and 99.29% degradation of 2,4-DNP, representing the effective elimination of these pollutants under visible light. This 10.73 μmol g⁻¹h⁻¹ photocatalytic conversion of CO₂ into CO is 10- and 12-fold that of NAO and g-CN, respectively. The 40% NAO/g-CN produced 1.58 times more 2,4-DNP degradation than bare g-CN, and 1.81 times more than bare NAO, at constant rate (k) values of 15.52 × 10⁻³, 5.33 × 10⁻³, and 6.27 × 10⁻³, respectively. This study opens new avenues to accurately modifying photogenerated charge separation directions by developing chemical bonding in direct scheme NiAl₂O₄/g-C₃N₄ structures for CO₂ photoreduction.