The production of formic acid/formate from electrochemical CO 2 reduction reaction (CO 2 RR) is fascinating but challenging due to the lack of highly active electrocatalysts. Herein, uniform PVP-capped bismuth nanospheres (PVP@Bi-NSs) with a capping-bonding synergy were optimally fabricated to enhance the CO 2 RR to formate. This study unveils the reaction process in Bi-based solution. It was found that the formation of PVP@Bi-NSs experienced five stages of Bi-O 8 (I), Bi-O 3 (II), Bi-O 4 (III), Bi-Bi 6 (IV), and PVP@Bi-NSs (V), corresponding to the nucleation in precursor solution, Bi(OH) 3 precipitate, decomposition to KBiO 2 , reduction to metallic Bi, and PVP coating, respectively. By solvothermal treatment and simply modulating the KOH concentration in the precursor, the hydrophilic ends of PVP molecules can be well bonded to the Bi nanoparticles (Bi-NPs) to form a PVP-capping layer. Compared with the Bi-NPs without PVP coating, this uniform PVP@Bi-NSs displays a higher activity with a maximal Faradaic efficiency (FE) of 92.5 % and part current density ( J formate ) of 158.2 mA cm −2 at −0.9 V vs. RHE in the flow cell as well as excellent stability, which is comparable to the state-of-the-art Bi-based catalysts. The maximum J formate can reach 280 mA cm −2 with an FE of 87.3 % at −1.2 V vs. RHE, meeting the needs of industrial current density. Further characterizations show that the capping effect of PVP contributed to the uniform distribution of nanosized PVP@Bi-NSs, increasing the electrochemical surface areas (ECSAs) and the numbers of CO 2 RR active sites. The bonding effect of PVP to Bi-NPs enhanced the hydrophobic property of PVP@Bi-NPs, boosting the CO 2 absorption and suppressing the hydrogen evolution reaction (HER). DFT calculations reveal that this fabricated structure facilitates the generation of *OCHO intermediate and benefits formate yield. This work provides a fascinating strategy for the design of Bi-based catalysts, enabling interface engineering toward high-efficiency CO 2 RR.
Yuan Zhao,Xuan Yang,Linyan Cui,Yali Sun,Qijun Song
Mercury ions (Hg 2+ ) and silver ions (Ag + ) are assigned to the highest toxicity class of heavy metal pollution. Here, a novel sensor is firstly developed for the simultaneous detection of coexisting Ag + and Hg 2+ in aqueous solution, depending on the catalytic properties of poly(vinyl pyrrolidone) (PVP)-capped platinum nanoparticle (Pt NPs) and the strong chelation of EDTA to Hg 2+ . PVP-capped Pt NPs exhibit uniform morphology and possess great intrinsic peroxidase-like activity in comparison to citrate-capped Pt NPs, PVP-capped Ru NPs and Ir NPs, attributing to the enhanced catalytic efficiency determined by loosely packed PVP and the excellent catalytic decomposition activities of H 2 O 2 . Hg 2+ and Ag + could induce remarkable inhibition of the peroxidase-like activity of Pt NPs by changing the electronic state of the active sites through metallophilic interactions. The selective and simultaneous detection of Hg 2+ and Ag + was realized via the addition of ethylenediaminetetraacetate (EDTA), which could successfully mask Hg 2+ but had negligible effect on Ag + . The proposed approach inspires new designs of novel catalytic nanoprobes for the multi-analyte assay of heavy metal ions .
In order to solve the problem that UO2 in direct ethanol fuel cell anode catalysts is easily lost in acidic solution, resulting in the degradation of catalytic performance, this paper prepared a C/UO2/PVP/Pt catalyst in three steps by adding polyvinylpyrrolidone (PVP). The test results by XRD, XPS, TEM and ICP-MS showed that PVP had a good encapsulation effect on UO2, and the actual loading rates of Pt and UO2 were similar to the theoretical values. When 10% PVP was added, the dispersion of Pt nanoparticles was significantly improved, which reduced the particle size of Pt nanoparticles and provided more ethanol electrocatalytic oxidation reaction sites. The test results by electrochemical workstation showed that the catalytic activity as well as the stability of the catalysts were optimized due to the addition of 10% PVP.
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