Ana Luísa S. Vieira

Juan J. Delgado

M. Fernando R. Pereira

Natalia Rey-Raap

Rafael G. Morais

Raquel P. Rocha

Rui S. Ribeiro

Portuguese

Repositório Aberto da Universidade do Porto

Catalysis: A pillar of modern societyEUROPA CAT202315th European Congress on Catalysis15th European Congress on CatalysisAugust 27 – September 1, 2023 Prague, Czech Republicbook of abstractsTailoring of Fe single-atoms on hollow carbon spheres for the oxygenreduction reactionRui S. Ribeiro1,2, Ana Luísa S. Vieira1,2, Juan J. Delgado3,4, Rafael G. Morais1,2, Natalia Rey-Raap5,Raquel P. Rocha1,2, M. Fernando R. Pereira1,21 LSRE-LCM - Laboratory of Separation and Reaction Engineering – Laboratory of Catalysis and Materials,Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.2 ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr.Roberto Frias, 4200-465 Porto, Portugal.3 IMEYMAT: Institute of Research on Electron Microscopy and Materials, University of Cádiz, E11510 PuertoReal, Cádiz, Spain.4 Departamento de Ciencia de Materiales, Ingeniería Metalúrgica y Química Inorgánica, University of Cádiz,E11510 Puerto Real, Cádiz, Spain.5 Instituto de Ciencia y Tecnología del Carbono, INCAR-CSIC, Francisco Pintado Fe 26, 33011 Oviedo, SpainKeywords: oxygen reduction, Fe electrocatalysts, single-atom catalyst, hollow carbon spheresIntroduction. Single-atom catalysts (SACs) have emerged as one of the most promising alternatives to noblemetal-based catalysts for highly efficient oxygen reduction reaction (ORR)[1]. A broad range ofnon-platinum group metal electrocatalysts has been developed, among which Fe−N−C nanostructures havebeen considered one of the most promising candidates. Most strategies for the synthesis of SACs needdelicate procedures. Therefore, developing strategies to tailor atomically better dispersed Fe sites inN-doped carbon supports is highly desirable. Herein, we reported the design of hollow carbon spheres withhighly stable Fe centres and enhanced catalytic activity in ORR.Experimental/methodology. Carbon spheres (CSs) were synthesized by sol-gel polycondensation throughStöber’s method, followed by thermal annealing and silica etching, according to a previously reportedprocedure [2]. The hollow CSs were then doped with nitrogen and Fe by adapting a procedure reportedelsewhere [3]. The effect of metal loading was studied by varying the proportion of metal precursor duringthe synthesis. In addition, the role of each precursor during the synthesis of the optimized electrocatalystwas elucidated by preparing additional materials in the absence of specific precursors. All samples werephysicochemically characterized using suitable techniques, including high-resolution transmission electronmicroscopy (HRTEM) and scanning transmission electron microscopy-high angle annular dark field imaging(STEM-HAADF) in combination with energy-dispersive X-ray spectroscopy (EDX). The catalytic performanceof the samples in ORR was assessed by electrochemical measurements using a three-electrode cellconfiguration in alkaline media.Results and discussion. The performance of the Fe-N-doped hollow CSs in ORR seems to be governed bythe quality of Fe species rather than the overall Fe load. Nitrogen seems to modulate the charge densitynearby the active sites and limit the agglomeration of the metal precursor during the synthesis. Glucoseenhances the metal-heteroatom coordination and subsequent dispersion of active sites on the carbonsurface. The activity of the best-performing metal-free CSs (CS7Fe-N) in ORR is still far from that obtainedwith the commercial noble metal-containing Pt/C. Nevertheless, it is thus noteworthy that CS7Fe-N revealedsuperior stability (97%) than Pt/C (92%) in the same conditions. Therefore, the methodology hereinreported opens a window of possibility for the development of highly stable ORR electrocatalysts based onsingle-atom Fe-N hollow CSs.AcknowledgmentsThis work was financially supported by project BiCat4Energy (PTDC/EQU-EQU/1707/2020), funded by national funds(PIDDAC) through FCT/MCTES; LA/P/0045/2020 (ALiCE), UIDB/50020/2020 and UIDP/50020/2020 (LSRE-LCM) fundedby national funds through FCT/MCTES (PIDDAC).References[1] Xiang Ao et al., ACS Nano 2019, 13, 11853−11862.[2] Vieira, Ana Luísa S. et al., J. Environ. Chem. Eng. 2022, 10, 107348.[3] Zhao, Lu et al., Nature Communications 2019, 10, 1278.

Tailoring of Fe single-atoms on hollow carbon spheres for the oxygen reduction reaction

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Tailoring of Fe single-atoms on hollow carbon spheres for the oxygen reduction reaction

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