Catalytic Reduction of 4-Nitrophenol to 4-Aminophenol Using Ag@α-Ti(HPO₄)₂·H₂O: Experimental and Computational Studies

Abstract

A simple hydrothermal method was developed for the synthesis of Ag supported on α-titanium bismonohydrogen orthophosphate monohydrate, Ag@α-Ti­(HPO4)2·H2O (Ag@α-TiP), using ilmenite (FeTiO3) mineral sand. The prepared nanoparticles (NPs) were characterized using powder X-ray diffraction, high-resolution transmission electron microscopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and diffuse-reflectance spectroscopy. The catalytic efficiency of Ag@α-TiP NPs in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol with sodium borohydride (NaBH4) in the presence/absence of ultraviolet–visible (UV–vis) radiation was examined. The reduction rate increased when Ag@α-TiP was present in the reaction mixture. The catalytic efficiency was further enhanced when the reaction mixture was exposed to UV–vis light. An ab initio molecular dynamic approach, coupled with slab model density functional theory (DFT) calculations, was used to find the optimal geometry for the model catalyst Ag4@α-TiP. The formation enthalpies and binding geometries for 4-NP and 4-nitrophenolate ion (4-NP–) on Ag4@α-TiP were calculated using DFT.

Efficient Removal and Recovery of Ag from Wastewater Using Charged Polystyrene-Polydopamine Nanocoatings and Their Sustainable Catalytic Application in 4-Nitrophenol Reduction

“…41 This conversion reaction proceeds through an intermediate step involving the formation of 4-nitrosophenol, which is driven by an electron transfer reaction. 42 The standard electrode potential E 0 for 4-NP/4-AP is −0.76 V, while for 43 The significant potential difference between the donor molecule (BH 4 − ) and the acceptor molecule (4-NP) creates a kinetic barrier to the reaction. 44 To overcome this kinetic barrier, precious metals are usually employed as catalysts to facilitate and promote the reaction by acceleration the electron transfer from the donor BH 4…”

“…This conversion reaction proceeds through an intermediate step involving the formation of 4-nitrosophenol, which is driven by an electron transfer reaction . The standard electrode potential E 0 for 4-NP/4-AP is −0.76 V, while for H 3 BO 3 /BH 4 – is −1.33 V . The significant potential difference between the donor molecule (BH 4 – ) and the acceptor molecule (4-NP) creates a kinetic barrier to the reaction .…”

Advances in 4-Nitrophenol Detection and Reduction Methods and Mechanisms: An Updated Review

“…In addition, they could predict the reaction mechanism through DFT calculations. Through theoretical calculations, Thanthrige et al 114 observed that the 4-NP molecule binds to silver favorable to the −NO 2 , creating a program to convert −NO 2 into −NH 2 . Chen et al, 115 who synthesized nitrogen-doped porous carbon through algae and DFT calculations, revealed the key character of the N atoms into the carbon structure to catalyze this reaction by adjusting the carbon atoms electronic configuration followed by endorsing the adsorption of 4nitrophenolate ions on the doped carbon material.…”