Hongzhou Yang,He Huang,Qing Wang,Lu Shang,Tierui Zhang,Shouguo Wang
3d transition metal single atom catalysts (SACs) (e.g. M = Fe, Co, Cu) are considered as promising catalysts for oxygen reduction reaction (ORR), among which Fe SACs display comparable performance to commercial Pt/C. However, Fe SACs still demand significant improvements in activity and stability for further industrial deployment. Herein, a Fe, Cu dual metal SAC was synthesized using a facile ligand-mediated method. Fe and Cu atoms were atomically dispersed on commercial carbon black in the form of FeN4 and CuN4 sites. Owing to the interactions between the adjacent Fe and Cu atoms co-existing in a very tiny area, the as-synthesized Fe, Cu dual metal SAC exhibited excellent ORR performance with a high half-wave potential of 0.926 V and good stability in 0.1 M KOH, which are significantly higher than that of the Fe-SAC or Cu-SAC control samples. Density function theory calculations showed that the Cu single atom can act as an electron donator enriching the electron density of Fe sites, thus endowing the Fe sites with optimized adsorption/desorption energy for ORR intermediates and thereby facilitating the ORR activity of FeCu-SAC. Moreover, a study on three typical commercial carbon substrates indicated that carbon support with high surface areas and hierarchical pore structure was beneficial for ORR. The excellent ORR activity and durability of FeCu-SAC enabled the constructed Zn–air battery to have a high power density of 201.4 mW cm−2 and high specific energy of 827.68 W h kg−1.
With tunable local electronic environment, high mass density of MN 4 sites, and ease of preparation, metal–organic conjugated coordinative polymer (CCP) with inherent electronic conductivity provides a promising alternative to the well-known M−N−C electrocatalysts. Herein, the coordination reaction between Cu 2+ and 1,2,4,5-tetraaminobenzene (TAB) was conducted on the surface of metallic Cu nanowires, forming a thin layer of CuN 4 -based CCP (Cu-TAB) on the Cu nanowire. More importantly, interfacial transfer of electrons from Cu core to the CuN 4 -based CCP nanoshell was observed within the resulting CuTAB@Cu, which was found to enrich the local electronic density of the CuN 4 sites. As such, the CuTAB@Cu demonstrates much improved affinity to the *COOH intermediate formed from the rate determining step; the energy barrier for C–C coupling, which is critical to convert CO 2 into C 2 products, is also decreased. Accordingly, it delivers a current density of −9.1 mA cm −2 at a potential as high as −0.558 V (vs. RHE) in H-type cell and a Faraday efficiency of 46.4% for ethanol. This work emphasizes the profound role of interfacial interaction in tuning the local electronic structure and activating the CuN 4 -based CCPs for efficient electroreduction of CO 2 .
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