Nonprecious Metal Catalysts for Oxygen Reduction in Heterogeneous Aqueous Systems

Abstract

A comprehensive review of recent advances in the field of oxygen reduction electrocatalysis utilizing nonprecious metal (NPM) catalysts is presented. Progress in the synthesis and characterization of pyrolyzed catalysts, based primarily on the transition metals Fe and Co with sources of N and C, is summarized. Several synthetic strategies to improve the catalytic activity for the oxygen reduction reaction (ORR) are highlighted. Recent work to explain the active-site structures and the ORR mechanism on pyrolyzed NPM catalysts is discussed. Additionally, the recent application of Cu-based catalysts for the ORR is reviewed. Suggestions and direction for future research to develop and understand NPM catalysts with enhanced ORR activity are provided.

Mixed Copper/Copper‐Oxide Anchored Mesoporous Fullerene Nanohybrids as Superior Electrocatalysts toward Oxygen Reduction Reaction

“…The ORR Tafel slope measured for Cu(15%)‐MFC 60 is 82 mV dec −1 , which is slightly higher than the Tafel slope determined for Pt (66 mV dec −1 ) (Figure S8a,b, Supporting Information). To further support the reported values, a similar trend in the ORR activity for copper supported/loaded carbon‐based catalysts has also been observed in the previous reports …”

Efficient Oxygen Reduction Reaction (ORR) Catalysts Based on Single Iron Atoms Dispersed on a Hierarchically Structured Porous Carbon Framework

“…[1][2][3][4] As one kind of non-PGM catalyst, Fe-based catalysts have been widely considered as ap romising candidate to replace the Pt-based ORR catalysts.H owever,F ebased catalysts still suffer from the poor electrochemical stability and unsatisfactory catalytic activity in acidic electrolyte. [1][2][3][4] As one kind of non-PGM catalyst, Fe-based catalysts have been widely considered as ap romising candidate to replace the Pt-based ORR catalysts.H owever,F ebased catalysts still suffer from the poor electrochemical stability and unsatisfactory catalytic activity in acidic electrolyte.…”

“…[3d, 6] Although iron phthalocyanine (FePc), one of the most popular Fe-based molecular catalysts, [7] could facilitate the ORR process via a4electron pathway,d emetalation of the catalytically active Fe atoms in FePc molecules was demonstrated to lead ar apidly declining activity. [1,9] To eliminate the demetalation and/or degradation of molecular catalysts,i ti s highly desirable to develop SA-Fec atalysts,i nw hich the coordinated Fe atoms are directly stabilized on carbon supports, [10] which can effectively prevent deactivation and facilitate electron transport. [1,9] To eliminate the demetalation and/or degradation of molecular catalysts,i ti s highly desirable to develop SA-Fec atalysts,i nw hich the coordinated Fe atoms are directly stabilized on carbon supports, [10] which can effectively prevent deactivation and facilitate electron transport.…”

Adsorbed Intermediates in Oxygen Reduction on Platinum Nanoparticles Observed by In Situ IR Spectroscopy

“…[1][2][3][4][5] Over the last five decades,e nvironmentally friendly low-temperature proton-exchange-membrane fuel cells have faced major performance challenges owing to the sluggish kinetics and high overpotential of the ORR, even at Pt nanoparticle cathodes. [7][8][9][10][11][12] However,t his effort is hindered by the poor understanding of the ORR mechanism, especially at real supported Pt nanoparticle electrodes.The complete reduction of O 2 to H 2 O is afour-electron process (O 2 + 4e À + 4H + !2H 2 O) and must therefore be composed of an umber of elementary electron transfer steps and intermediate species.S everal different mechanistic pathways have been proposed for acidic conditions.One possibility is the initial dissociative adsorption of O 2 to form Pt À Os pecies,w hich subsequently undergo reduction and protonation. [7][8][9][10][11][12] However,t his effort is hindered by the poor understanding of the ORR mechanism, especially at real supported Pt nanoparticle electrodes.The complete reduction of O 2 to H 2 O is afour-electron process (O 2 + 4e À + 4H + !2H 2 O) and must therefore be composed of an umber of elementary electron transfer steps and intermediate species.S everal different mechanistic pathways have been proposed for acidic conditions.One possibility is the initial dissociative adsorption of O 2 to form Pt À Os pecies,w hich subsequently undergo reduction and protonation.…”