ABSTRACT
Development of highly efficient electrocatalysts for treating urea-rich wastewater is an important problem in environmental management and energy production. In this work, an iron-nickel alloy (Fe-Ni alloy) was synthesized via soft-template cetyltrimethylammonium bromide (CTAB)-assisted precipitation using low-temperature calcination. The as-synthesized nanoalloy was characterized by X-ray diffraction (XRD), which revealed the formation of a face-centered cubic (FCC) structure of the Fe-Ni alloy; field emission-scanning electron microscopic (FE-SEM) analysis revealed the spherical shape of the Fe-Ni alloy; high-resolution transmission electron microscopy (HR-TEM) revealed the average size to be â¼33.09 nm; and X-ray photoelectron spectroscopy (XPS) showed the presence of Fe, Ni, C, and O components and their chemical composition and valence states in the Fe-Ni alloy. The electrochemical urea oxidation reaction (UOR) was investigated by conducting linear sweep voltammetry (LSV) tests on the synthesized electrocatalysts with different Ni/Fe ratios in alkaline electrolytes with urea. The potential required to reach a current density of 10 mA cm-2 is 1.27 V vs RHE, which demonstrates the higher electrochemical activity of the Fe-Ni alloy compared to other individual compounds. This could be due to CTAB which improved the structural stability and synergetic and electronic effects in the nanoscale. This study will further contribute to renewable energy generation technology with long-term energy sustainability and also opens up great potential for reducing water pollution.
ABSTRACT
Global warming challenges are fueling the demand to develop an efficient catalytic system for the reduction of CO2 , which would contribute significantly to the control of climate change. Herein, as-synthesized bismuthoxide-decorated graphene oxide (Bi2 O3 @GO) was used as an electro/thermal catalyst for CO2 reduction. Bi2 O3 @GO is found to be distributed uniformly, as confirmed by scanning electron and transmission electron microscopic analysis. The X-ray diffraction (XRD) pattern shows that the Bi2 O3 has a ß-phase with 23.4â m2 g-1 BET surface area. Significantly, the D and G bands from Raman spectroscopic analysis and their intensity ratio (ID /IG ) reveal the increment in defective sites on GO after surface decoration. X-ray photoelectron spectroscopic (XPS) analysis shows clear signals for Bi, C, and O, along with their oxidation states. An ultra-low onset potential (-0.534â V vs. RHE) for the reduction of CO2 on Bi2 O3 @GO is achieved. Furthermore, potential-dependent (-0.534, -0.734, and -0.934 vs. RHE) bulk electrolysis of CO2 to formate provides Faradaic efficiencies (FE) of approximately 39.72, 61.48, and 83.00 %, respectively. Additionally, in time-dependent electrolysis at a potential of -0.934 versus RHE for 3 and 5â h, the observed FEs are around 84.20 % and 87.17 % respectively. This catalyst is also used for the thermal reduction of CO2 to formate. It is shown that the thermal reduction provides a path for industrial applications, as this catalyst converts a large amount of CO2 to formate (10â mm).
ABSTRACT
4-Nitrophenol (4-NP) is present in most industrial waste water resources as an organic pollutant, and is a highly toxic and environmentally hazardous pollutant. Herein, we report that bismuth oxide (Bi2O3) decorated multi-walled carbon nanotubes (Bi2O3@MWCNTs) are the most prominent electrocatalyst for 4-NP electroreduction in acidic conditions. The electrocatalyst is synthesized by a simple chemical reduction method using ethylene glycol as a capping agent. The synthesized Bi2O3@MWCNTs electrocatalyst has been well-characterized by Fourier-transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy. Bi2O3@MWCNTs have a cubic structure which is confirmed by XRD. TEM imaging reveals Bi2O3 NPs are ~2 nm in size, are grown on MWCNTs and that these nanoparticles are active toward 4-NP electroreduction. The electrochemical studies by cyclic voltammetry measurements show that the Bi2O3@MWCNTs electrocatalyst can sense 4-NP at a very low potential i.e., -0.17 vs. saturated calomel electrode (SCE). Furthermore, electroanalytical parameters like scan rate and concentration dependence were studied with electrochemcial impedance spectroscopy (EIS) and the effect of pH on cathodic current was examined under experimental conditions. The lower limit of detection (LOD) was found to be 0.1 µM for the Bi2O3@MWCNTs nanomaterial and is excellent toward 4-NP. The present study has applications for reducing water pollution and for sorting out related issues.
