Highly efficient electrochemical gas reduction on a three-dimensional foam electrode: mechanism and application for the

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ORIGINAL PAPER

Highly efficient electrochemical gas reduction on a three-dimensional foam electrode: mechanism and application for the determination of hazardous mercury in complex matrix Lei Cheng 1 & Xin-an Yang 1 & Meng-ting Shi 1 & Wang-bing Zhang 1,2 Received: 7 May 2020 / Accepted: 18 August 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020

Abstract For the first time a nickel foam electrode (NFE) is applied in the field of electrochemical vapor generation (EVG) to carry out the electrochemical vapor phase conversion of mercury. Systematical electrochemical and morphological research has demonstrated that the specific surface area of the NFE was several times larger than that of the metal/non-metal electrode with the same geometric size. At the same time, the 3D porous channel composed of multi-layer nickel wire ensures the full contact between reactant and interface. The evident enhancement of spectral signals on a Ni electrode (283%), compared with Pt (27%) and graphite (109%), confirmed that the NFE effectively enhances the yield of mercury reduction. The NFE exhibits low limit of detection (0.017 μg L−1) and a wide linear range (0.2–20 μg L−1) with recoveries of actual samples in the range 87.8–117% towards Hg2+. Although the NFE has no advantage in electronic transmission and catalytic performance, its excellent stability, especially anti-interference and other characteristics, is sufficient for the analysis of hazardous mercury in complex matrix including certified reference materials and real samples. Keywords Electrochemical vapor generation . Mercury . Nickel foam electrode . Highly efficient conversion

Introduction The realization of high sensitive and accurate analysis of ultratrace mercury has been widely concerned due to the strong biological toxicity [1–3]. However, as one of the important detection methods, atomic spectrum technology still faces many challenges. For instance, the

* Xin-an Yang [email protected] * Wang-bing Zhang [email protected] Lei Cheng [email protected] Meng-ting Shi [email protected] 1

Department of Applied Chemistry, Anhui University of Technology, Maanshan 243002, Anhui, People’s Republic of China

2

Institute of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002, Anhui, People’s Republic of China

stability, purity, and price of sodium borohydride may lead to more uncertainty in traditional mercury vapor generation technology [4]. Although the above problems are avoided because electrolytic vapor generation (EVG) does not use chemical reducing reagent, it has no advantage in trace pollutant analysis. Compared with the common chemical vapor generation (CVG) technology, as an example, the spectral detection signal value of arsenic, mercury, and other elements from EVG can only reach 10~70% [5–7]. The mechanism is not clear, but the reactants can be fully mixed through a variety of ingenious designed CVG reactors at high speed [8]. In the process of electrosynthesis, the probability of metal ions participating in the in