Fig. 2: DFT calculations and electrocatalytic performance of MPc MDEs.

a The molecular structure of MPc, M refers to the metal center. b The free energy diagram for NH₂OHRR on various MPcs at 0 V vs. RHE. The ellipse substrates represent the active sites on the electrocatalyst. The black, blue and grey balls represent the N, O and H atoms, respectively. c SEM image of ZnPc aggregated electrocatalyst (AE). d SEM image of ZnPc MDE. e HAADF-STEM image of ZnPc MDE. The bright spots correspond to the Zn center of ZnPc. f The electrocatalytic performances of MPc MDEs. The left side illustrates the required potentials in NH₂OHRR to achieve a current density of −1.0 mA cm⁻² in an electrolyte of 1.0 M KOH containing 33 mM NH₂OH (150 mL), R_u = 10.0 ± 3.4 Ω. The right side displays their FE(NH₂OH) in NO₃RR at a current density of −100 mA cm⁻² in an electrolyte of 1.0 M KOH + 1.0 M KNO₃ (14 mL), R_u of CoPc, FePc and ZnPc MDE are 5.5 ± 0.1 Ω, 4.4 ± 0.1 Ω and 4.7 ± 0.4 Ω. The metal content: ~ 0.3 wt.%. Three individual measurements were taken with various working electrodes, and the average (mean) values are presented with the standard deviation as error bars. g UV−Vis spectra of colorimetric quantification of NH₂OH. The orange color shows the presentation of NH₂OH in solution, which can reduce Fe³⁺ to Fe²⁺, forming an orange complex with 1,10-phenanthroline. The abbreviation “arb. units” refers to “arbitrary units”.