Characterization of oxidized reticulated vitreous carbon electrode for oxygen reduction reaction in acid solutions

Underpotential Deposition of 3D Transition Metals: Versatile Electrosynthesis of Single-Atom Catalysts on Oxidized Carbon Supports

Use of single-atom catalysts (SACs) has become a popular strategy for tuning activity and selectivity toward specific pathways. However, conventional SAC synthesis methods require high temperatures and pressures, complicated procedures, and expensive equipment. Recently, underpotential deposition (UPD) has been investigated as a promising alternative, yielding high-loading SAC electrodes under ambient conditions and within minutes. Yet only few studies have employed UPD to synthesize SACs, and all have been limited to UPD of Cu. In this work, a flexible UPD approach for synthesis of mono- and bi-metallic Cu, Fe, Co, and Ni SACs directly on oxidized, commercially available carbon electrodes is reported. The UPD mechanism is investigated using in situ X-ray absorption spectroscopy and, finally, the catalytic performance of a UPD-synthesized Co SAC is assessed for electrochemical nitrate reduction to ammonia. The findings expand upon the usefulness and versatility of UPD for SAC synthesis, with hopes of enabling future research toward realization of fast, reliable, and fully electrified SAC synthesis processes.

Removal of urea from dilute streams using RVC/nano-NiOx-modified electrode

Reticulated vitreous carbon (RVC), a high surface area electrode (40 cm²/cm³), has been modified with nickel oxide nanoparticles (nano-NiO_x) and used for electrochemical oxidation of urea from alkaline solution. For the cyclic voltammetry measurements, the used dimensions are 0.8 cm × 0.8 cm × 0.3 cm. The purpose was to offer high specific surface area using a porous open network structure to accelerate the electrochemical conversion. NiO_x nanoparticles have been synthesized via an electrochemical route at some experimental conditions. The morphological, structural, and electrochemical properties of the RVC/nano-NiO_x are characterized by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), cyclic voltammetry (CV), and potentiostatic measurements. The fabricated electrode, RVC/nano-NiO_x, demonstrates high electrocatalytic activity towards urea oxidation in an alkaline electrolyte. The onset potential of the RVC/nano-NiO_x compared to that of the planar GC/NiO_x is shifted to more negative value with higher specific activity. The different loadings of the NiO_x have a substantial influence on the conversion of urea which has been evaluated from concentration-time curves. The urea concentration decreases with time to a limit dependent on the loading extent. Maximum conversion is obtained at 0.86 mg of NiO_x per cm³ of the RVC matrix.