Durability challenges and perspective in the development of PGM-free electrocatalysts for the oxygen reduction reaction

Establishing reactivity descriptors for platinum group metal (PGM)-free Fe–N–C catalysts for PEM fuel cells

“…The latter are defined so that fuel cell stacks with PGM-free ORR catalysts become cost-and performancecompetitive with PGM-based catalysts, even for the highly demanding automotive application. [4][5][6][12][13][14][15][16][17][18][19][20][21][22] The most prominent example of PGM-free ORR electrocatalysts for acidic medium is the family of iron-(or cobalt-) and nitrogen-doped high surface area carbon matrix, typically referred as ''Fe-N-C'' catalysts, with atomically-dispersed Fe cations coordinated with nitrogen atoms as the recognized most active sites. 5,[23][24][25][26][27][28][29][30][31][32] Unlike PGM-based single atom catalysts, where the atoms exist in a carbon matrix as a sole atoms 33,34 or dimeric compounds, 35 iron generally has to be coordinated with hetero atoms.…”

“…36, Despite the impressive achievements in the catalytic performance of Fe-N-C catalysts, further improvements in their ORR activity and, in particular, durability are needed before their large-scale deployment in commercial PEMFCs becomes a reality. 12,26,[61][62][63] Over the past decades, studies to identify more active Fe-N-C catalysts have largely relied on empirical approaches involving the systematic variation of elemental precursors and/or synthesis conditions to prepare Fe-N-C materials and their correlation with the resulting kinetic current density ( J kin ) and other lump performance metrics of ORR catalysts. 7,36,[64][65][66] While this approach has had some success in the early stages of Fe-N-C materials development, it now seems to have reached its limitation, with stalled progress in the power and durability performance of Fe-N-C cathodes in PEMFCs in the last years, despite intense international efforts.…”

Methanol-Tolerant M–N–C Catalysts for Oxygen Reduction Reactions in Acidic Media and Their Application in Direct Methanol Fuel Cells

“…In the last few years, many PGM-free formulations were synthesized and investigated for ORR, showing great activity in the rotating disk configuration compared to Pt catalysts, but the performance, durability, and stability were very low in a complete polymer electrolyte fuel cell (PEFC) [23]. More recently, the M-N-C catalysts (M being a transition metal such as Fe or Co) showed great promise owing to their good ORR activity and performance in PEFCs [24][25][26][27][28][29][30][31]. On the other hand, there are only a few reports on the performance results of a DMFC equipped with PGM-free catalysts at the cathode, likely due to the relatively recent research interest in this topic.…”

Electrocatalytic Oxygen Reduction at Multinuclear Metal Active Sites Inspired by Metalloenzymes

“…Synthetic non-PGM electrocatalysts have advantages over PGM-based electrocatalysts and/or metalloenzymes: low material costs, small footprints (volume per active site) and tolerance to poisoning chemicals such as CO [105] and KSCN [106]. However, the improvement of the ORR activity and durability [107] of non-PGM electrocatalysts remains challenging despite many papers on them. Recent studies on 57 Fe Mössbauer spectroscopy and low-temperature CO pulse chemisorption and temperature-programmed desorption (TPD) of Fe/N/C electrocatalysts revealed their TOFs of ca.…”