Scheme 2.

MXene-based materials for ORR

(A and B) Fe Mössbauer transmission spectra and their deconvolution of pristine FePc and FePc/Ti₃C₂T_x.

(C) X-band ESR spectra of pristine Ti₃C₂T_x, FePc, and FePc/Ti₃C₂T_x.

(D) Schematic representation of the spin transition of partial Fe(II) on Ti₃C₂T_x.⁸² Copyright 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

(E) LSV curves of different catalysts.

(F) The open-circuit voltage and peak power density at different temperatures.

(G) The free energy changes for ORR and (H) the PDOS of Fe 3d orbital for FeN₃O and FeN₃O-O-Ti. The blue dotted lines denote the d-band centers, while the gray dotted line denotes the Fermi level.⁴ Copyright 2022 Wiley-VCH GmbH.

(I) In situ reconstruction of Mo₂CT_x:Fe catalyst during reaction.

(J) Anodic-going polarization curves for the electrodes with deposited Mo₂CT_x:Fe or Mo₂CT_x.

(K) XRD patterns of Fh/C that indicate the presence of graphite and graphite oxide phases. The inset shows a SEM image of the Fh/C material (the scale bar is 1 μm).⁸⁴ Copyright 2021 American Chemical Society