Engineering [Fe(CN)6]3− vacancy via free-chelating agents in Prussian blue analogues on reduced graphene oxide for efficient oxygen evolution reaction

Enhanced Electrochemical Water Oxidation Activity by Structural Engineered Prussian Blue Analogue/rGO Heterostructure

“…To estimate the Ni and Fe species contents, the obtained XPS results were fitted by XPS PEAK software ( Figure 2 ). Two major peaks were found by split-peak fitting located at 855.7 eV for the Ni2p3/2 peak and Ni2p1/2 at 874.0 eV corresponding to the Ni-N coordination in NiN 6 [ 19 ], and the other two peaks (860.62 and 880.09 eV) are the satellite peaks corresponding to the aforementioned two peaks ( Figure 2 a) [ 33 ]. Comparing the Ni 2p high-resolution peak, the Ni 2p 3/2 and 2p 1/2 peak positions are shifted to higher energy for the graphene composite compared with PBA NiFe 2-1, indicating that the interaction between Ni and rGO results in a decreased electron density for Ni and increased the oxidation state of Ni ( Figure 2 c) [ 34 , 35 ].…”

“…Comparing the Ni 2p high-resolution peak, the Ni 2p 3/2 and 2p 1/2 peak positions are shifted to higher energy for the graphene composite compared with PBA NiFe 2-1, indicating that the interaction between Ni and rGO results in a decreased electron density for Ni and increased the oxidation state of Ni ( Figure 2 c) [ 34 , 35 ]. The high oxidation state of Ni is favorable for receiving electrons, which contributes to the formation of NiOOH active material, and can increase the charge transfer between the electrode material and the electrolyte [ 19 , 36 ].…”

“…Regarding the 2p peak of Fe, two peaks of Fe 2p3/2 and Fe2p1/2 shown in Figure 2 b generated by orbital cleavage can be observed at 708.4 and 721.9 eV corresponding to the coordination of Fe 2+ -C [ 19 , 37 ]. Additionally, there is another peak at 711.1 eV, corresponding to Fe 3+ and indicating the presence of mixed valence states of Fe 2+ and Fe 3+ in the composites ( Figure 2 d) [ 38 ].…”

“…However, PBA has a poor charge transfer capacity, which restricts its intrinsic catalytic efficacy. Loading PBA materials on highly conductive materials is an effective way to improve their charge transfer capability [ 19 , 20 ].…”

“…High-resolution Ni 2p and Fe 2p spectra of PBA NiFe 2-1, respectively; Table S1: catalyst performance of analogous materials; Table S2: the calculated C dl ECSA values of as-obtained PBA materials. References [ 18 , 17 , 19 , 43 , 44 ] are cited in Supplementary Material.…”