Enhancing oxygen evolution reaction electrocatalytic performance with vanadium-doped Co/CoO encapsulated in carbon nanorod

A portable magnetic electrochemical sensor for highly efficient Pb(II) detection based on bimetal composites from Fe-on-Co-MOF

The practical, sensitive, and real-time detection of heavy metal ions is an essential and difficult problem. This study presents the design of a unique magnetic electrochemical detection system that can achieve real-time field detection. To enhance the electrochemical performance of the sensor, Fe2O3@C-800, Co/CoO@/C-600, and CoFe2O4@C-600 magnetic composites were synthesized using three MOFs precursors by the solvothermal method. And the morphology structure and electrochemical properties of as-prepared magnetic composites were researched by X-ray diffraction (XRD), Scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), specific surface area and porosity analyzer (BET) and differential pulse voltammetry (DPV). The results shown that these composites improve conductivity and stability while preserving the MOFs basic frame structure. Compared with the monometallic MOFs-derived composites, the synergistic effect of the bimetallic composite CoFe2O4@C-600 can significantly enhance the electrochemical performance of the sensor. The linear range for the detection of lead ions was 0.001-60 μM, and the detection limit was 0.0043 μM with a sensitivity of 22.22 μA μM·cm-2 by differential pulse voltammetry. The sensor has good selectivity, stability, reproducibility and can be used for actual sample testing.

"d-electron interactions" induced CoV2O6-Fe-NF for efficient oxygen evolution reaction

The investigation of cost-effective, highly efficient, and environmentally friendly non-noble-metal-based electrocatalysts is imperative for oxygen evolution reactions (OER). Herein, CoV₂O₆ grown on nickel foam (NF) was selected as the fundamental material, and Fe²⁺ is introduced through a simple Fe³⁺ immersion treatment to synthesize CoV₂O₆-Fe-NF. Fe²⁺ is transformed into high oxidation state Fe^(2+δ)+ due to interactions between the 3d electrons of transition metals. In situ Raman spectroscopy analysis reveals the specific process of OER in the presence of Fe^(2+δ)+. Being in a higher oxidation state, Fe^(2+δ)+ provides more active sites, which is beneficial for the reaction between water molecules and the reactive sites of the electrocatalyst, ultimately enhancing the accelerated OER process. CoV₂O₆-Fe-NF exhibited an overpotential of only 298 mV at 100 mA cm^-2 in 1 M KOH electrolyte, which is lower than that of CoV₂O₆-NF (348 mV), as well as the comparative samples: Fe-NF (390 mV) and NF (570 mV). The exploration of high performance, triggered synergistically by the cooperative effect of transition metal 3d electrons, provides insights into the design of transition metal electrocatalysts for highly efficient OER.