Ternary alloy (FeCoNi) nanoparticles supported on hollow porous carbon with defects for enhanced oxygen evolution reaction

Medium entropy FeCoNi nanoalloy supported on reduced graphene oxide for efficient electrochemical detection of roxarsone in food samples

Herein, a novel FeCoNi(b)-800 ternary metal nanoalloy was uniformly mixed with reduced graphene oxide (RGO) to synthesize the FeCoNi(b)-800@RGO(2:1) composite. The addition of RGO not only stopped the accumulation of FeCoNi(b)-800 alloy, but also heightened the electrocatalytic activity of composite. Particularly, the FeCoNi(b)-800@RGO(2:1) composite displayed the significantly strong electrocatalytic capacity for the reduction of roxarsone (ROX). Furthermore, the FeCoNi(b)-800@RGO(2:1) composite possessed enough porosity and metal catalytic sites, facilitating the transport and electrochemical reduction of the ROX. Thus, the FeCoNi(b)-800@RGO(2:1) composite modified glassy carbon electrode (FeCoNi(b)-800@RGO(2:1)/GCE) showed the superb electrochemical detection effect for ROX with relatively wide working range (0.1-1500 μM) and low detection limit (0.013 μM). Importantly, the FeCoNi(b)-800@RGO(2:1)/GCE sensor could accurately determine the contents of ROX in actual pork, chicken, duck and egg samples, indicating that it had good suitability in food safety monitoring.

Movable-type printing method to fabricate ternary FeCoNi alloys confined in porous carbon towards oxygen electrocatalysts for rechargeable Zn-air batteries

Transition metal-based carbon catalysts are a promising class of electrocatalysts to enhance the efficiency of energy conversion and storage devices. However, it remains a challenging task to develop multi-metal alloy catalysts. Herein, ternary FeCoNi alloy nanoparticles (NPs) confined in nitrogen-doped carbon (NC) catalysts were fabricated via a facile movable-type printing method, where a range of transition metals confined in NC catalysts was prepared using the same technique except for the adjustment of the metal precursors. Due to the unique electronic structure and significant active sites of the medium-entropy alloy, the FeCoNi-NC catalysts demonstrated highly efficient bifunctional electrocatalytic activities for the oxygen reduction (E1/2 = 0.838 V) and evolution (Eoverpotential = 330 mV, 10 mA cm-2) reactions, which were comparable to those of Pt/C and RuO2. Moreover, the FeCoNi-NC-based liquid rechargeable ZABs displayed a substantial power density of 231.2 mW cm-2, and the homemade flexible ZABs also exhibited outstanding activity and cycling durability. Thus, this movable-type printing method is suitable for constructing a variety of multi-metal-based catalysts for metal air batteries.

Co-Fe3C pair sites catalyst with heterometallic dual active sites for efficient oxygen reduction reaction

Newly emerging metal-based pair sites catalysts show great potential because they can provide more metal active centers with synergistic effect for green catalysis, compared with single site catalysts. However, both the synthesis and catalytic mechanisms of the pair sites catalyst with new structural features need to be developed vigorously to promote the desired chemical reactions, especially carbon-based metal catalysts for green energy storage and conversion devices. Herein, we constructed highly active Co-Fe3C pair sites on N-doped graphite catalyst (CNCo-Fe3C) by a two-step strategy, which have electron interactions of heterometallic atoms and can play better synergistic effect. X-ray absorption spectra and density functional theory (DFT) calculation further identify the presence of heterometallic active sites in the pair sites catalyst, resulting in electron redistribution and positive d-band center due to the electron interactions. The more positive d-band center model predicts the optimization of the adsorption energy of oxygen-containing intermediates, and reduces the energy barrier of the determining step. This further results in superior oxygen reduction reaction (ORR) performance with a half-wave potential of 0.90 V versus reversible hydrogen electrode (vs.RHE) and superior long-term stability for about 20 h with only 2.3 % decrease at 0.75 V vs.RHE in 0.1 M KOH solution. Additionally, it also shows significant peak power density of 124 mW cm-2 and prominent cycling stability performance exceeding 400 h at 5 mA cm-2 in the Zn-air battery (ZAB) test, which is higher than that of Pt/C catalyst. This work provides a new idea for the regulation of intrinsic activity of non-noble metal ORR catalysts through the synergistic effect of the pair sites.

Ultrafast synthesis of halogen-doped Ru-based electrocatalysts with electronic regulation for hydrogen generation in acidic and alkaline media

Developing a facile and time-saving method for preparing hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts can accelerate the practical applications of hydrogen energy. In this study, halogen (X = F, Cl, Br and I) doped Ru-RuO₂ on carbon cloth (CC) (X-Ru-RuO₂/MCC) was synthesized via an ultrafast microwave-assisted method for 30 s. Particularly, the doped Br (Br-Ru-RuO₂/MCC) significantly improved the electrocatalytic performances of the catalyst through the regulation of electronic structures. Then, the Br-Ru-RuO₂/MCC catalyst featured HER overpotentials of 44 mV and 77 mV in 1.0 M KOH and 0.5 M H₂SO₄, and the OER overpotential of 300 mV at 10 mA cm^-2 in 1.0 M KOH. This study provides a novel method for developing of halogen-doped catalysts.