Anchoring Carboxyl Functionalized Gold-Aryl Nanoparticles to Graphene Oxide Platforms for Environmental Nanoremediation

Graphene oxide (GO) was decorated with gold-aryl (Au-C) nanoparticles AuNPs-COOH by sodium borohydride reduction of aryldiazonium tetrachloroaurate(III) salt at room temperature in aqueous solutions. BET (Brunauer-Emmett-Teller) measurements supported the anchoring of GO by AuNPs modified with carboxyl functional groups; surface area dropped significantly. Morphology of AuNPs-COOH/GO nanocomposite (NC) was probed using AFM and TEM and images showed surface roughness and wrinkling. Molecular dynamics (MD) calculations endowed support of favorable wrinkling at the edges and carboxyl intercalation to GO surface of types p-p, hydrogen bonding, and hydrophobic interactions. Solvent accessible surface area calculations (SASA) of GO showed a decrease in total surface area, in agreement with BET results. Environmental nanoremediation of the catalytic reduction of nitrophenol and the electrocatalytic reduction of CO₂ (model pollutants) were investigated. The apparent rate constants K_app of the four catalytic reduction cycles of nitrophenol were measured. The highest value is 1.17 × 10^-1 min^-1 for the first cycle which decreased to 4.49 × 10^-2 min^-1 for the fourth cycle. Electrocatalytic studies revealed that the NC enhanced the CO₂ reduction. The NC exhibited higher current densities in the CO₂ solution saturated (48 mA/cm²) compared to N₂ (37 mA/cm²), indicating its superior catalytic activity in CO₂ reduction.