Facile green synthesis of a novel NiO and its catalytic effect on methylene blue photocatalytic reduction and sodium borohydride hydrolysis

Abstract

NiO nanoparticles were synthesized from pine cone extract by green synthesis method, which is a simple, cost-effective, environmentally friendly and sustainable method. The particle size of NiO nanoparticles was determined to be in the range of 10–25 nm by X-diffraction differential and transmission electron microscope analysis, and the bandgap energy of NiO nanoparticles was determined to be 2.66 eV. The catalytic effect of NiO nanoparticles in both microwave-assisted sodium borohydride hydrolysis and photocatalytic reduction of methylene blue was examined and it was determined that they had a high catalytic effect in both applications. It was determined that the hydrogen production rate in sodium borohydride hydrolysis was 1135 mL/g/min. The activation energy of sodium borohydride hydrolysis is 29.69 kJ/mol and 29.59 kJ/mol for the nth-order and Langmuir Hinshelwood kinetic models, respectively. In the photocatalytic reduction of methylene blue with NaBH4, it was determined that the reduction did not occur in the absence of a catalyst, but in the presence of the catalyst, the reduction occurred 98% in 3 min. It was determined that NiO nanoparticles were used five times in the photocatalytic reduction of methylene blue and the reduction efficiency for the fifth time was 93%. It was determined that the photocatalytic reduction of methylene blue was pseudo-first order and the rate constant was 1.63 s−1. It was determined that NiO nanoparticles synthesized by the environmentally friendly green synthesis method can be used as catalysts for two different applications.