Unraveling the impact of the Pd nanoparticle@BiVO4/S-CN heterostructure on the photo-physical & opto-electronic properties for enhanced catalytic activity in water splitting and one-pot three-step tandem reaction

Abstract

Herein, a Pd nanoparticle-embedded SBVCN-37 heterostructure photocatalyst was synthesized and employed in the water-splitting reaction and for the synthesis of imines via a one-pot tandem reaction involving the photocatalytic reduction of nitrobenzene and oxidation of benzyl alcohol, followed by their condensation reaction. The embedded Pd nanoparticles (mean diameter ∼ 5-7 nm) act as an electron mediator and enhance the catalytic activity of SBVCN-37 during the oxidation and reduction reactions. The experimental results confirm that the light-induced holes owing to the favourable redox potential of the catalyst oxidize N2H4 to N2 and liberate H+ ions, which subsequently react with photogenerated electrons to facilitate the reduction of nitrobenzene. The obtained quantum yields for benzyl alcohol oxidation and nitrobenzene reduction were calculated to be 2.08% and 6.53% at λ = 420 nm light illumination, respectively. Furthermore, the obtained apparent quantum yields for the OER and HER were calculated to be 10.22% and 12.72% at 420 nm, respectively, indicating the excellent potential of the investigated photocatalyst for solar fuel production. Photoelectrochemical (PEC) and time-resolved and steady-state photoluminescence measurements reveal that the optimum amount of Pd nanoparticles over SBVCN-37 is the crucial factor for achieving the highest photocurrent response, lowest charge transfer resistance, and efficient carrier mobility, leading to prominent catalytic activity. Furthermore, the Mott-Schottky (M-S) analysis confirmed that the deposition of Pd nanoparticles effectively reduced the over-potential and fine-tuned the band edge potential required for the HER and OER reactions, respectively.