Generalizable Descriptors of Highly Sensitive Detection of As(III) over Transition-Metal Single Atoms: A Combined Density Function Theory and Gradient Boosting Regression Approach

In-situ precipitation zero-valent Co on Co2VO4 to activate oxygen vacancies and enhance bimetallic ions redox for efficient detection toward Hg(II)

Despite the widespread utilization of variable valence metals in electrochemistry, it is still a formidable challenge to enhance the valence conversion efficiency to achieve excellent catalytic activity without introducing heterophase elements. Herein, the in-situ precipitation of Co particles on Co2VO4 not only enhanced the concentration of oxygen vacancies (Ov) but also generated a greater number of low-valence metals, thereby enabling efficient reduction towards Hg(II). The electroanalysis results demonstrate that the sensitivity of Co/Co2VO4 towards Hg(II) was measured at an impressive value of 1987.74 μA μM-1 cm-2, significantly surpassing previously reported results. Further research reveals that Ov acted as the main adsorption site to capture Hg(II). The redox reactions of Co2+/Co3+ and V3+/V4+ played a synergistic role in the reduction of Hg(II), accompanied by the continuous supply of electrons from zero-valent Co to expedite the valence cycle. The Co/Co2VO4/GCE presented remarkable selectivity towards Hg(II), with excellent stability, reproducibility, and anti-interference capability. The electrode also exhibited minimal sensitivity fluctuations towards Hg(II) in real water samples, underscoring its practicality for environmental applications. This study elucidates the mechanism underlying the surface redox reaction of metal oxides facilitated by zero-valent metals, providing us with new strategies for further design of efficient and practical sensors.

Iron oxide-supported gold nanoparticle electrode for simultaneous detection of arsenic and sulfide on-site

The environmental behavior of arsenic (As) has garnered significant attention due to its hazardous nature. The fate of As often couples with sulfide, thus co-detecting arsenic and sulfide on-site is crucial for comprehending their geochemical interactions. While electrochemical methods are suitable for on-site chemical analysis, there currently exists no electrode capable of simultaneously detecting both arsenic and sulfide. To address this, we developed a dual-metal electrode consisting of iron oxide-encased carbon cloth loaded with gold nanoparticles (Au/FeOx/CC) using the electrochemical deposition method. This electrode enables square wave stripping voltammetry (SWASV) binary detection of As and sulfide. Comparison experiments reveal that the reaction sites for sulfide primarily reside on FeOx, while the interface synergy of iron oxide and gold nanoparticles enhances the response to arsenite (AsIII). Arsenate (AsV) is directly reduced to As0 on Fe0, obviating the need for an external reducing agent. The electrode achieves detection limits of 1.5 μg/L for AsV, 0.25 μg/L for AsIII, and 11.6 μg/L for sulfide at mild conditions (pH 7.8). Field validation was conducted in the Tengchong geothermal hot spring region, where the electrochemical method exhibited good correlation with the standard methods: Total As (r = 0.978 vs. ICP-MS), AsIII (r = 0.895 vs. HPLC-ICP-MS), and sulfide (r = 0.983 vs. colorimetric method). Principal component analysis and correlation analysis suggest that thioarsenic, could potentially be positive interferents for AsIII. However, this interference can be anticipated and mitigated by monitoring the abundance of sulfide. The study provides new insights and problems for the electrochemical detection of coexisted As and sulfide.

A novel tetragonal T-C2N supported transition metal atoms as superior bifunctional catalysts for OER/ORR: From coordination environment to rational design

Single-atom catalysts with particular electronic structures and precisely regulated coordination environments delivering excellent activity for oxygen-evolution reaction (OER) and oxygen-reduction reaction (ORR) are highly desirable for renewable energy applications. In this work, a novel tetragonal carbon nitride T-C2N monolayer with remarkable stability was predicted by using the RG2 method. Inspired by the well-defined atomic structures and just right N4 aperture of T-C2N substrate, the electrocatalytic performance of a series of transition metal single-atoms anchored on porous T-C2N matrix (TM@C2N) have been systematically investigated. In addition, machine learning (ML) method was employed with the gradient boosting regression GBR model to deeply explore the complex controlling factors and offer direct guidance for rational discovery of desirable catalysts. On this basis, the coordination environment of the central TM active sites has been tailored by incorporating heteroatoms. Impressively, the Co@C2N/B-C, Rh@C2N/SC and Rh@C2N/SN exhibit significantly enhanced OER/ORR activity with notably low ηOER/ηORR of 0.39/0.32, 0.26/0.35 and 0.37/0.27 V, respectively. Our work provides insights into the rational design, data-driven, performance regulation, mechanism analysis and practical application of TMNC catalysts. Such a systematic theoretical framework can also be expanded to many other kinds of catalysts for energy storage and conversion.