3D ordered macro-/mesoporous carbon supported Ag nanoparticles for efficient electrocatalytic oxygen reduction reaction

Efficient and recyclable Ni-Ce-Mn-N modified ordered mesoporous carbon electrode during electrocatalytic ozonation process for the degradation of simulated high-salt phenol wastewater

In this study, an efficient and stable NiO/CeO₂/MnO₂-modified nitrogen-doped ordered mesoporous carbon (NOMC) particle electrode was developed, in which the metal oxides were mosaicked within the pore channels by one-pot skeleton hybridization, and the comodification of NiO/CeO₂/MnO₂/N was found to improve the electrocatalytic activity and stability of the particle electrode. The improved stability of the ordered mesoporous carbon towards pore collapse was applied to the degradation of simulated high-salt phenol wastewater by an electrocatalytic ozonation process using simple binder pelletization. The modified ordered mesoporous carbon shows a specific surface area of 269.7 m² g^-1 and a pore size of 3.17 nm, and SEM and TEM were used to show that the mesoporous structure is well maintained and the metal nanoparticles are well dispersed. The electrochemically active area of the Ni_2%/Ce_0.5%/Mn_2.5%-NOMC particle electrode reaches 224.65 mF cm^-2, which indicates that NiO improves the capacitance of the ordered mesoporous carbon and accelerates the electron transfer efficiency. Encouragingly, the phenol removal efficiency is found to reach up to 93.0% for 60 min over a wide range of pH values, with an initial phenol concentration of 150 mg L^-1, low current (0.03 A) and fast reaction rate (0.0895 min^-1), and the presence of CeO₂ ameliorates the low activity of the particle electrode under acidic conditions. These results indicate that the presence of pyridine-N and β-MnO₂ effectively mitigates carbon corrosion and improves electrode stability, as the accumulation of large amounts of ·OH at 20 min and the maintenance of a degradation efficiency of more than 90% after eight cycles provides a viable solution for the widespread practical application of ordered mesoporous carbon particle electrodes.

Nitrite reduction over Ag nanoarray electrocatalyst for ammonia synthesis

Electrochemical reduction of nitrite to ammonia can simultaneously achieve ammonia synthesis and N-contaminant removal under mild conditions, which has attracted widespread attention but still lacks efficient catalysts. In this work, Ag nanoarray using NiO nanosheets array on carbon cloth as support is reported as an efficient electrocatalyst to selectively reduce nitrite to ammonia. In 0.1 M NaOH with 0.1 M NO₂^-, such catalyst exhibits a maximum ammonia yield of 5,751 μg h^-1 cm^-2 (57,510 μg h^-1 mg_Ag^-1) and high Faradaic efficiency up to 97.7 %. Density functional theory calculations applied to uncover the catalytic mechanism of NO₂^- reduction reaction on Ag.

Simultaneous electrochemical detection of gallic acid and uric acid with p-tert-butylcalix[4]arene-based coordination polymer/mesoporous carbon composite

Design and synthesis of an efficient electrocatalyst for simultaneous determination of gallic acid (GA) and uric acid (UA) is vital in the biological field. Herein, we synthesized a new p-tert-butylcalix[4]arene-based metal-organic electrocatalyst (Mn-L@MC) by combining Mn-L (H₄L = tetrakis[(2-biphenylcarboxyl)oxy]-p-tertbutylcalix[4]arene) and mesoporous carbon (MC) via a simple mechanical grinding method. Synergistic effect between Mn-L and MC made the Mn-L@MC composite behave high-efficiency electrocatalytic performance toward simultaneous detection of GA and UA. Under optimal experimental conditions, the Mn-L@MC-2 electrode material featured relatively wide linear range (0.5-90 µM) for the two analytes, and low determination limits of 0.043 µM for GA and 0.059 µM for UA. The remarkable electrochemical detection behavior of Mn-L@MC-2 electrode material toward GA and UA are comparable to those known sensors containing precious metals. The Mn-L@MC-2 material exhibited high selectivity, superior reproducibility, and acceptable stability during the determination of the two analytes. The sensor was assembled to simultaneously detect GA and UA in healthy human urine with satisfactory recoveries.

Graphitic Carbon Nitride as a Platform for the Synthesis of Silver Nanoclusters

Graphitic carbon nitride (CN) synthetized by the thermal polycondensation of melamine at 550 °C for 4 h was further exfoliated by heating at 500 °C for 3 h. Silver cations were adsorbed on the exfoliated graphitic carbon nitride (CNE) and then reduced by sodium borohydride forming silver nanoclusters (NCs) with a size of less than 1 nm. The NCs were located on the CNE surface and did not change the CNE properties except for its pore size distribution and thereby specific surface area (SSA). The Ag NCs were able to collect the photoinduced electrons of CNE and thus reduce their recombination with the holes. It was also documented by the increase in the CNE photocatalytic activity in terms of the degradation of antibiotic Ofloxacin. This study demonstrates the ability of CNE to serve as a platform for a simple and fast synthesis of Ag NCs without any stabilizing compounds.