Quantifying the density and utilization of active sites in non-precious metal oxygen electroreduction catalysts.
Carbon materials doped with transition metal and nitrogen are highly active, non-precious metal catalysts for the electrochemical conversion of molecular oxygen in fuel cells, metal air batteries, and electrolytic processes. However, accurate measurement of their intrinsic turn-over frequency and active-site density based on metal centres in bulk and surface has remained difficult to date, which has hampered a more rational catalyst design. Here we report a successful quantification of bulk and surface-based active-site density and associated turn-over frequency values of mono- and bimetallic Fe/N-doped carbons using a combination of chemisorption, desorption and (57)Fe Mössbauer spectroscopy techniques. Our general approach yields an experimental descriptor for the intrinsic activity and the active-site utilization, aiding in the catalyst development process and enabling a previously unachieved level of understanding of reactivity trends owing to a deconvolution of site density and intrinsic activity.
Department of Chemistry, The Electrochemical Energy, Catalysis and Material Science Laboratory, Chemical Engineering Division, Technical University Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany.
Nastaran Ranjbar
NR
Sahraie
Department of Chemistry, Technical University Darmstadt, Jovanka-Bontschits-Street 2, 64287 Darmstadt, Germany.|Department of Materials and Earth Science, Technical University Darmstadt, Jovanka-Bontschits-Street 2, 64287 Darmstadt, Germany.
Ulrike I
UI
Kramm
Department of Chemistry, The Electrochemical Energy, Catalysis and Material Science Laboratory, Chemical Engineering Division, Technical University Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany.
Julian
J
Steinberg
School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189, China.
Yuanjian
http://orcid.org/0000-0003-2932-4159
Y
Zhang
Department of Chemistry, Division of Functional Materials, Technical University Berlin, Hardenbergstr. 40, 10623 Berlin, Germany.
Arne
A
Thomas
Department of Chemistry, The Electrochemical Energy, Catalysis and Material Science Laboratory, Chemical Engineering Division, Technical University Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany.
Tobias
T
Reier
Department of Chemistry, Division of Functional Materials, Technical University Berlin, Hardenbergstr. 40, 10623 Berlin, Germany.
Jens-Peter
JP
Paraknowitsch
Department of Chemistry, The Electrochemical Energy, Catalysis and Material Science Laboratory, Chemical Engineering Division, Technical University Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany.
Peter
P
Strasser