Electrodeposition of silver particles from alkaline aqueous solutions and their electrocatalytic activity for the reduction of nitrate, bromate and chlorite ions

Electrochemical Selective Nitrate Reduction: Pathways to Nitrogen and Ammonia Production

Nitrate (NO3 -) contamination from industrial, agricultural, and anthropogenic activities poses significant risks to human health and ecosystems. While traditional NO3 - remediation methods are effective, they often generate secondary pollutants and incur high costs. Electrochemical NO3 -reduction (ECNR) offers a sustainable alternative, converting NO3 - into environmentally benign nitrogen (N2) or valuable ammonia (NH3). This review explores recent advancements in selective ECNR pathways for NO3 --to-N2and NO3 --to-NH3 conversion, focusing on mechanistic insights, electrocatalyst development, and optimization strategies. Key factors influencing ECNR performance, such as electrode materials, electrolyte composition, and hydrogen evolution inhibition, are discussed. Additionally, the review highlights the role of single-atom, bimetallic, and nanostructured catalysts in enhancing faradaic efficiency, total N2 removal, and selectivity, with particular attention to Pd-Cu systems. Strategies to address challenges like low selectivity and catalyst degradation are also explored. This review underscores the potential of ECNR as a viable alternative to the energy-intensive Haber-Bosch process for NH3 production, aligning with global sustainability goals. Finally, we identify research gaps and propose future directions for improving the efficiency, stability, and scalability of ECNR technologies.

Silver deposition optimization process on ultrananocrystalline diamond applied to nitrate reduction

Nitrate is a serious contaminant of ground and surface water, which cause high concern in the field of health and environmental protection. In this work, a ternary composite of silver/boron-doped ultrananocrystalline diamond/reticulated vitreous carbon (Ag/B-UNCD/RVC) was prepared and its electrocatalytic activity for nitrate reduction was examined. B-UNCD films were grown by hot filament chemical vapour deposition technique on RVC after a substrate seeding process improvement using 4 nm diamond powder. Compared to conventional 0.25 µm diamond seeding, this new procedure allowed uniform RVC coverage avoiding its etching process during diamond growth, in addition to obtaining more reproductive electrodes. In order to improve the catalytic effect of B-UNCD/RVC electrodes for nitrate reduction, silver deposition was performed on B-UNCD surface after oxidation for 10, 20 and 30 min in 0.5 mol L^-1 H₂SO₄ solution using a potential of 2 V vs. Ag/AgCl. The most oxidized diamond film (30 min of oxidation) presented the highest silver deposit and particle adhesion. Thus the electrochemical response to nitrate of B-UNCD/RVC oxidized for 30 min was compared to that of RVC and B-UNCD/RVC electrodes showing the important Ag influence in the catalytic process.

Oxides in silver–graphene nanocomposites: electrochemical signatures and electrocatalytic implications

Electrochemical investigations establish that the electroreduction of oxide form of silver present in Ag-reduced graphene oxide nanoassembly enhances its efficiency towards electro-oxidation of ascorbic acid (AA).

Development of an automated on-line electrochemical chlorite ion sensor

A sensor system for the automatic, in-line, determination of chlorite ion is reported. Electroanalytical measurements were performed in electrolyte-free liquids by using an electrochemical probe (EC), which enables in-line detection in high-resistance media such as disinfected water. Cyclic voltammetry scan rate studies suggest that the current arising from the oxidation of chlorite ion at an EC probe is mass-transfer limited. By coupling FIA with an EC probe amperometric cell, automated analysis was achieved. This sensor is intended to fulfill the daily monitoring requirements of the EPA DBP regulations for chlorite ion. Detection limits of 0.02-0.13 mg/L were attained, which is about one order of magnitude below the MRDL. The sensor showed no faradaic signal for perchlorate, chlorate, or nitrate. The lifetime and stability of the sensor were investigated by measuring calibration curves over time under constant-flow conditions. Detection limits of <0.1 mg/L were repeatedly achieved over a period of three weeks.