Increasing reductive Fe(ii)/Co(ii) sites on P-doped FeCo2O4−x nanosheets to accelerate the valence cycle for the electroanalysis of As(iii)

Abstract

Modulating active sites via doping heteroatoms to improve the catalytic capabilities of nanomaterials has attracted attention from various fields. However, the relationship between the excellent catalytic performance and the changes in the structures of materials caused by doping was ignored. Herein, we designed a competent strategy for promoting the electrochemical analysis of As(III) by FeCo₂O_4−x with P-doping (P-FeCo₂O_4−x). P-FeCo₂O_4−x modified glassy carbon electrodes (P-FeCo₂O_4−x/GCE) exhibited an excellent sensitivity for As(III) of 1.240 μA ppb⁻¹, which was almost one order of magnitude higher than that of FeCo₂O_4−x/GCE. Besides, P-FeCo₂O_4−x displayed excellent selectivity toward As(III) compared to other typical heavy metal ions (HMIs), with excellent stability, repeatability, practicality, and anti-interference ability. X-ray photoelectron spectroscopy revealed that P-doping made more electrons transfer from P to adjacent Fe(III) and Co(III) via Fe–P and Co–P bonds, thus obtaining more high-activity ions of Fe(II) and Co(II) in P–FeCo₂O_4−x, along with the formation of abundant oxygen vacancies (Ov). As(III) adsorbed on Ov interacted with P sites to form Fe–P–As and Co–P–As bonds, during the process of detection. Subsequently, the enhanced valance cycle of Fe(II)/Fe(III) and Co(II)/Co(III) caused by increasing reduction ions further improved the surficial redox for highly-efficient electrocatalysis of As(III), thereby acquiring a satisfactory electrochemical performance. This work helps to understand the relationship between the internal change of sensitive interfaces caused by heteroatomic doping and excellent catalytic performance, which provides guidance for designing high-activity electrocatalytic interfaces for ultrasensitive environmental HMIs analysis.