Use of plant based analytes for the synthesis of NiO nanoparticles in catalyzing electrochemical H2O2 production

This work demonstrates that the use of plant based analytes for the synthesis of weak ferromagnetic microporous (75% pores within 1.52 to 2 nm) NiO nanoparticles (NPs, mean 12.11-14.48 nm). This process is inexpensive and simple and, uses the extracted analytes from Sechium edule which is rich in ascorbic acid (AA). The characterizations of NiO NPs were performed for its structural, functional, thermal, and morphological attributes. Ni(OH)(2) was formed at a higher pH by the ligand exchange between AA(-) and OH- which was completely converted to NiO NPs after the calcination (500 degrees C for 2 h) as supported by the mass spectra of analytes and control-experiment. The synthesized NiO NPs were immobilized on the graphite surface and tested for its electrocatalytic activity for the production of H2O2 in an acidic pH (1.5 <= pH <= 4.5, 0.5 M Na2SO4 and O-2 flow rate 1.0 LPM). From the cyclic voltammetric tests (vs. Ag/AgCl), it was found that O-2 reduction took place at a low overpotential (0.125 V) which was independent on the solution pH, but the cell current was diminishing beyond the optimal pH of 2.5.There was a remarkable increase in the cell current (3.5 times) and current efficiency (61% higher) of H2O2 formation with graphite/NiO NPs cathode than the bare graphite and, the current efficiency didn't decrease (5-7%) much during electrolysis. The limiting current density (1.42 A/m(2)) was independent on the surface area of graphite/NiO NPs cathodes and, the mass transfer coefficient (k(m)) and thickness (delta) of O-2 diffusion layer were 0.955 x 10(-)(5) m/s and 209 mu m, respectively.