Effect of the Preparation Conditions on the Catalytic Properties of CoPt for Highly Efficient 4-Nitrophenol Reduction

Abstract

CoPt alloys with Pt contents from 15 to 90% were prepared using low-cost electrochemical deposition. Different samples were synthesized from electrochemical baths at pH = 2.5 and 5.5 in a solution with and without saccharin as an additive. The morphology, composition and crystalline structure of the as-prepared samples were investigated by High Resolution—Scanning Electron Microscopy (HR-SEM), Atomic Force Microscopy (AFM), Ultra-high Resolution—Transmission Electron Microscopy (UHR-TEM), Energy-Dispersive X-ray Spectroscopy (EDX), and X-ray Diffraction (XRD). XRD investigations revealed that fcc crystalline structure transforms into hcp crystalline structure when the pH of the electrochemical bath is increased from 2.5 to 5.5 as well as when saccharin is added to the electrochemical bath. The catalytic performance of the CoPt alloys for the nitro to amino phenol compounds conversion was investigated for all the prepared samples, and the results show that the conversion degree increases (from 11.4 to 96.5%) even though the Pt content in the samples decreases. From the samples prepared from the electrochemical bath with saccharin, a study regarding the effect of contact time was performed. The results indicated that after only 5 min, the CoPt sample prepared at pH = 5.5 in the presence of saccharin completely converted the nitro compound to an amino compound.

High Catalytic Activity of CoxPt100−x Alloys for Phenolic Compound Reduction

“…This data are in good agreement with those presented in Ref. [26]. As can be observed from Figure 3, all the as-deposited materials present diffractions peaks at 2Θ = 43.5 and 44.5.…”

“…As additive, we used sodium saccharine 0.00389M. The electrodeposition process parameters (such as applied potential, time on and time off), as well as the electrochemical bath characteristics (such as composition, pH value and additives), have been selected based on previously obtained results [25,26], where we found that the saccharin addition into the electrochemical bath improves the thin film layer mechanical properties (the saccharin is a well-known additive used for smoothening and stress relieving electrodeposited thin films). We also found that the saccharine favors the preparation of the CoPt alloys with a hcp crystalline structure.…”

“…The catalytic activity of the P1-P4 materials was established using the previously proposed method [26]. For the catalytic experiments, a volume of 2.5 mL of distilled water was put into contact with P1-P4 materials and further mixed with 40 µL of 4-NP (5 mM and 10 mM concentrations).…”

Obtaining and Characterizing the Osmium Nanoparticles/n–Decanol Bulk Membrane Used for the p–Nitrophenol Reduction and Separation System

“…The choice of p –nitrophenol as the target substance is justified both by the practical importance of the reaction, and by the fact that there are multiple and excellent studies that thus allow the comparative evaluation of the results [ 37 , 38 , 39 , 40 ].…”

“…The reduction of p -nitrophenol, with hydrogen obtained in situ from sodium borohydride (NaBH 4 ), was studied to determine the catalytic performance of various nanomaterials [ 14 , 15 , 16 , 37 , 38 , 39 , 40 , 45 ].…”