The Competition between 4-Nitrophenol Reduction and BH4− Hydrolysis on Metal Nanoparticle Catalysts

Abstract

Assessing competitive environmental catalytic reduction processes via NaBH4 is essential, as BH4− is both an energy carrier (as H2) and a reducing agent. A comprehensive catalytic study of the competition between the borohydride hydrolysis reaction (BHR, releasing H2) and 4-nitrophenol reduction via BH4− on M0- and M/M′ (alloy)-nanoparticle catalysts is reported. The results reveal an inverse correlation between the catalytic efficiency for BH4− hydrolysis and 4-nitrophenol reduction, indicating that catalysts performing well in one process exhibit lower activity in the other. Plausible catalytic mechanisms are discussed, focusing on the impact of reaction products such as 4-aminophenol and borate on the rate and yield of BH4− hydrolysis. The investigated catalysts were Ag0, Au0, Pt0, and Ag/Pt-alloy nanoparticles synthesized without any added stabilizer. Notably, the observed rate constants for the 4-nitrophenol reduction on Ag0, Ag-Pt (9:1), and Au0 are significantly higher than the corresponding rate constants for BH4− hydrolysis, suggesting that most reductions do not proceed through surface-adsorbed hydrogen atoms, as observed for Pt0 nanoparticles. This research emphasizes the conflicting nature of BH4− hydrolysis and reduction processes, provides insights for designing improved catalysts for competitive reactions, and sheds light on the catalyst properties required for each specific process.

Deciphering the mechanistic insights of 4-nitrophenol reduction catalyzed by a 1D–2D Bi2S3 nanostructured catalyst

“…Also, competition exists between the hydrogen evolution reaction from sodium borohydride hydrolysis and 4-NP reduction. 61 Therefore, 0.053 mmol of NaBH 4 was chosen as the best dose for further studies. Under optimized reaction conditions, BS-1 takes 20 min for 99.9% reduction of 4-NP and exhibits a first-order apparent rate constant ( k app ) of 0.152 min −1 (Fig.…”

Hydrogen adsorption on various transition metal (111) surfaces in water: a DFT forecast

“…7b, clearly point out that the suspension of the Au 0 -NPs after the completion of the HER has still enough reducing power to reduce some of the PNP into para-aminophenol, PAP, as the band formed at 300 nm proves. 95,96 Surprisingly, when the experiment with Ag 0 -NPs is carried out, Fig. 7a, PAP was not formed.…”