Noble-Metal-Free MOF-74-Derived Nanocarbons: Insights on Metal Composition and Doping Effects on the Electrocatalytic Activity Toward Oxygen Reactions

• Published in: ACS applied energy materials Vol. 2; no. 3; pp. 1854 - 1867
• Main Authors: Abdelkader-Fernández, Víctor K, Fernandes, Diana M, Balula, Salete S, Cunha-Silva, Luís, Pérez-Mendoza, Manuel José, López-Garzón, F. Javier, Pereira, M. Fernando, Freire, Cristina
• Format: Journal Article
• Language: English
• Published: American Chemical Society 25-03-2019
• Subjects: fuel cells; renewable energy; oxygen evolution reaction; oxygen reduction reaction; MOF-derived carbons; electrocatalysis
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.8b02010

The continuous and dramatic increase of global demand for energy resources makes it urgent to develop affordable nanostructured materials to act as efficient electrocatalysts (ECs) in the energy-related reactions. Metal–organic framework (MOF) template pyrolysis for the production of nanostructured carbon-based materials is a very promising methodology to produce carbon-based ECs. Herein, we report the preparation, characterization (XPS, CHNS analysis, ICP-OES, XRD, TEM, and SEM/EDS), and application as oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) ECs of a plethora of nanostructured carbon materials derived from RT-synthesized (RT, room temperature) MOF-74 with different metal compositions, Co, Ni and Co/Ni, and dopant heteroatoms, N–, S– and N/S-dual-doping. This has allowed the study of the aforementioned parameters’ influence on the OER and ORR electrocatalytic activity in alkaline medium. Highly synergetic effects have been detected in two cases: (1) when N/S-dual-doped carbon is produced from a monometallic Co-MOF-74 template, N,S–Co@C, and (2) when an undoped carbon is derived from bimetallic Co/Ni-MOF-74, Co/Ni@C. These two samples achieve OER performances with η10 = 0.41 and 0.44 V, respectively, along with Tafel slopes of 101 and 93 mV dec–1, being close to the state-of-art OER catalyst performance. In addition, ORR tests showed that the effect of heteroatom doping on ORR activity is always positive, regardless of metal composition.