Oxygen Reduction Reaction on Metal and Nitrogen–Doped Carbon Electrocatalysts in the Presence of Sodium Borohydride

Abstract

Metal and nitrogen-doped carbons electrocatalysts (M-N-C, where M is Fe or Co) are investigated for the oxygen reduction reaction (ORR) in alkaline conditions in the presence of borohydride ions (BH4-). The electrochemical properties of the Fe-N-C and CoN -C catalysts were investigated by cyclic voltammetry and rotating disk electrode 2 techniques: their ORR electrocatalytic activity was bridged to their physico-chemical properties, mainly type of metallic center (Fe vs. Co), structure (atomic dispersion vs. nanoparticles) and BET surface area. It is found that Fe-N-C catalysts have the best performances for the ORR electrocatalysis, even in presence of BH4anions. The atomically-dispersed Fe-and Co-containing electrocatalysts reach better BH4-tolerance than their counterparts baring nanoparticles. For the atomically dispersed Fe-N-C electrocatalysts, the lowest BET surface area material generates a slight advantage of ORR mass activity and a poor (and desired) activity for borohydride oxidation reaction (BOR).

Review on the Degradation Mechanisms of Metal-N-C Catalysts for the Oxygen Reduction Reaction in Acid Electrolyte: Current Understanding and Mitigation Approaches

“…In addition, oxidation of the carbon surface might negatively impact the transport properties of the AL, due to increased hydrophilicity in particular. Finally, it is noteworthy that the exposure of Fe-N-C to H 2 O 2 in alkaline conditions did not modify its ORR activity and selectivity, opening interesting perspectives for application in anion-exchange membrane fuel cell cathodes, with advantages over PGM-catalysts with respect to their general insensitivity to fuels such as methanol − and NaBH 4 …”

Electrochemical transformation of Fe-N-C catalysts into iron oxides in alkaline medium and its impact on the oxygen reduction reaction activity

“…[24] Recently, we reported that, in alkaline electrolyte, catalysts based on metal NPs surrounded by a N-C shell (Metal@N-C, with Metal = Fe or Co) feature slightly higher ORR mass activity (MA) than some Metal-N-C catalysts with atomically-dispersed Metal-NxCy sites (metal = Fe, Co), [25] and carbon-supported Pt NPs (Pt/C). [26][27][28][29][30][31] The Fe-N-C materials are also tolerant to anodic fuels (such as alcohols and borohydride) [28,[31][32][33] and to common contaminants and impurities, which are present in reformed H2 or in air. [13,34] Thus, the interest in Metal-N-C catalysts for application in AEMFCs is rapidly rising, with recently reported high performance.…”

“…[13,34] Thus, the interest in Metal-N-C catalysts for application in AEMFCs is rapidly rising, with recently reported high performance. [33,[35][36][37][38][39] The advantage of Metal-N-C catalysts over PGM-containing catalysts in alkaline electrolyte is not limited to the first few hours of operation but extends far beyond that. Using the protocols from the Fuel Cell Commercialization Conference of Japan (FCCJ) [40], Zadick et al [41] and Lafforgue et al [42] reported severe degradation of PGM NPs supported on high surface area carbon.…”

Direct borohydride fuel cells: A selected review of their reaction mechanisms, electrocatalysts, and influence of operating parameters on their performance

“…The literature is extremely rich in studies of non-Pt ORR catalysts, and several have been successfully demonstrated in AEM-based or separator-based DBFCs. Without being exhaustive, one can cite Fe-N-C or Co-N-C [46], MnO2 [42,47],…”