Theory‐Guided Regulation of FeN₄Spin State by Neighboring Cu Atoms for Enhanced Oxygen Reduction Electrocatalysis in Flexible Metal–Air Batteries

Abstract

Iron, nitrogen‐codoped carbon (Fe−N−C) nanocomposites have emerged as viable electrocatalysts for the oxygen reduction reaction (ORR) due to the formation of FeNxCy coordination moieties. In this study, results from first‐principles calculations show a nearly linear correlation of the energy barriers of key reaction steps with the Fe magnetic moment. Experimentally, when single Cu sites are incorporated into Fe−N−C aerogels (denoted as NCAG/Fe−Cu), the Fe centers exhibit a reduced magnetic moment and markedly enhanced ORR activity within a wide pH range of 0–14. With the NCAG/Fe−Cu nanocomposites used as the cathode catalyst in a neutral/quasi‐solid aluminum–air and alkaline/quasi‐solid zinc–air battery, both achieve a remarkable performance with an ultrahigh open‐circuit voltage of 2.00 and 1.51 V, large power density of 130 and 186 mW cm−2, and good mechanical flexibility, all markedly better than those with commercial Pt/C or Pt/C‐RuO2 catalysts at the cathode.

Manipulating the Spin State of Fe Sites via Fe–O–Si Bridge Bonds for Enhanced Polysulfide Redox Kinetics in the Li–S Battery

“…Compared with Fe foil, FeO and Fe 2 O 3 , the metallic Fe−Fe bond and Fe−O−Fe bond are not observed in FM and FM-Hal, which apparently show only the Fe−O bond corresponding to the first-shell coordination (Figure 1d). 27,28 Meanwhile, the fitting R and k space suggest that the Fe−O bond length is slightly shorter and the coordination number is higher in FM-Hal than those in FM (Figure S5 and Table S3), further confirming the strong interface interaction between Hal and anchored Fe-MOFs nanosheets. Based on the abovementioned results and analysis, we further construct the schematic instruction of the structure of FM-Hal (Figure S6).…”

In-Situ Grafting of Single-Atomic Titanium–Nitrogen Moiety onto Carbon Nanostructures for Efficient Photovoltaic Devices

“…Furthermore, Ti−N/O coordination number N = 3.0 extracted from quantitative EXAFS curve-fitting analysis and the wellresolved intensity maximum revealed by WT analysis consolidated the preserved edge-hosted Ti 1 N 2 OH moiety (model 1 in Figure 3d) during the carbonization process (Figure 3f, Figure S8, Table S1). According to the N 1s XPS deconvolution analysis 23 (Figure S9, the distinct area percent clearly reveals a dominant pyridinic N species in Ti 1 /NC-SAC), an in-plane pyridinic Ti 1 N 3 moiety on graphene was also constructed (model 2 in Figure 3d). We calculated the XANES spectrum and found a considerable mismatch with the experimental one.…”

Orbital Occupancy and Spin Polarization: From Mechanistic Study to Rational Design of Transition Metal-Based Electrocatalysts toward Energy Applications

“…Besides, as the paramagnetic triplet dioxygen constitutes most of the natural oxygen (and therefore being the main reactant for ORR), the spin properties of electrocatalytic materials would affect the adsorption of O 2 on the catalytic surface . Indeed, several theoretical studies have illustrated that the adsorption and subsequent dissociation of dioxygen depend strongly on the electron configuration of the surface metal atoms. − For instance, using spin-polarized DFT to investigate the chemisorption and dissociation of oxygen on the M-N 4 moiety (M = Mn, Fe, Co) on graphene, Orellana showed that the chemisorption and dissociation of O 2 are mediated by metal–oxygen spin coupling . The chemisorption of the O 2 molecule was examined in two equilibrium positions: one with an O atom bonded to the metal center (endon) and another with both O atoms bonded to the metal center (sideon) and with different spin multiplicities of the adducts.…”