Figure illustrates the two-step synthetic strategy for the dualmetal catalyst. First, the precursor FeNi/ZIF-8@MWCNTs was fabricated by in-situ functionalization of ZIF-8 with Fe 3+ and Ni 2+ . The resulting dodecahedral ZIF-8 particles were anchored to the surface of MWCNTs, resulting in a self-assembled macroporous 3D structure. Calcination of this precursor at 950 o C for 3 h under Argon flow gave the target composite, hereafter referred to as FeNi-NC@MWCNT. Note that during calcination, the precursor particles were converted to 2D graphene-like nanosheets, which were mechanically stabilized by the interlinking MWCNTs. Also note that the Zn 2+ metal present in the original ZIF-8 was removed from the sample by evaporation during pyrolysis, contributing to the formation of a highly porous N-doped carbon matrix. After pyrolysis, the composite was washed repeatedly with aqueous HCl (1.5 M) and deionized water to remove any metal salts and metal nanoparticles. To understand the impact of the dual Fe/Ni metal sites, we also synthesized the monometallic Fe-NC@MWCNTs and Ni-NC@MWCNTs as reference samples. Also, to assess the impact of the MWCNTs, we also fabricated FeNi/ZIF-8 composites in the absence of MWCNTs. The morphology and structure of the catalysts were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure shows the SEM image of FeNi-NC@MWCNT, the structure of ZIF-8 nanoparticles was well maintained during Fe/Ni functionalization and pyrolysis. The ZIFderived nanoparticles are interspersed within the MWCNTs, resulting in a hierarchical porous structure. Note that the MWCNTfree reference FeNi-NC shows similar particle features (SI, Figure ), indicating the introduction of MWCNTs does not affect catalyst morphology. Note that SEM and TEM analysis do not indicate any metal or metal oxide nanoparticles in both FeNi-NC@MWCNT (SI, Figure ) and FeNi-NC (SI, Figure ). To probe the dispersion of the Fe and Ni sites, we used aberrationcorrected high-angle annular dark-field scanning TEM (AC-HAADF-STEM). As shown in Figure , a large number of uniformly distributed bright spots are clearly identified in FeNi-NC@MWCNT, which are assigned to isolated single Fe and/or Ni atoms and/or dual single atoms sites (FeNi sites). The corresponding element mapping analysis confirms the uniform dispersion of Fe, Ni, C and N in the carbon matrix derived from ZIF-8 (SI, Figure ). Also, inductively coupled plasma optical emission spectroscopy (ICP OES) was used to determine the mass percentage of Fe (0.57 wt.-%) and Ni (0.62 wt.-%) in FeNi-NC@MWCNT (SI, Table ). Figure represents the powder X-ray diffraction (pXRD) pattern of FeNi-NC@MWCNT, the profile shows two broad diffraction peaks at around 30° and 42° attributed to the (002) and (101) lattice planes of graphitic carbon. No peaks of crystalline Fe or Ni metal-based particles were observed in FeNi-NC@MWCNT, which is in line with the microscopic analyses. The Raman spectrum of FeNi-NC@MWCNT (Figure ) primarily shows two characteristic bands with the D band at approximately 1350 cm⁻¹ and the G band at approximately 1595 cm⁻¹. The D band represents defects or/and disorders in the carbon lattice, while the G band corresponds to ordered sp²-hybridized graphitic carbon atoms. The ratio between D band and G band (ID/IG) for FeNi-NC@MWCNT is higher than for the reference samples (See SI, Figure for more details), indicating the introduction of more structural defects during synthesis. The specific surface area and pore size distribution of the catalysts were measured by N2 sorption (SI, Figure ). Analysis of the data showed that the introduction of MWCNTs significantly increased the specific surface area of FeNi-NC@MWCNT. Also, FeNi-NC@MWCNT contains more micropores and mesopores than the FeNi-NC reference (SI, Figure ), which can alter mass transfer (particularly of gaseous reagents) within the composite. ) can be divided into five separate species, that is pyridinic N (398.7 eV), metal-coordinated N (399.8 eV), graphitic N (400.9 eV), pyrrolic N (402.1 eV) and oxidized N (405.5 eV). The peak located at 399.8 eV provides further evidence for the binding of Fe and/or Ni species to nitrogen centers in FeNi-NC@MWCNT. To further identify the chemical state and coordination environment of the Fe and Ni sites in FeNi-NC@MWCNT, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses were conducted. As shown in Figure , the Fe K-edge XANES spectra reveal that the Fe energy absorption edge position of FeNi-NC@MWCNT is located between Fe foil and Fe2O3, indicating the average oxidation state of Fe is between Fe(0) and Fe2O3 (+3). The inset graph in Figure highlights the weak pre-edge feature at ~7115 eV, which is close to iron phthalocyanine (FePc) and can be assigned to the charge transfer from ligands to metal atoms and metal 1s to 3d transition in FeNi-NC@MWCNT. Similarly, the XANES spectra of the Ni K-edge for FeNi-NC@MWCNT give an average valence of Ni between Ni(0) and Ni(+2). Note that the nickel XANES data show comparable features to nickel phthalocyanine (NiPc), suggesting the existence of Ni-Nx coordination environment in the FeNi-NC@MWCNT (Figure ). Notably, the pre-edge peak at ~8335 eV of Ni curve in FeNi-NC@MWCNT is higher than that of NiPc, implying a distorted D4h symmetry in Ni central atoms, which possibly results from Fe-Ni interactions (Figure insert). Figure displays the Fourier-transformed (FT) k 2 -weighted Fe K-edge EXAFS spectra in Rspace. Compared with the FePc reference, a pronounced shoulder of the Fe K-edge at 1.4 Å indicates the Fe-Nx coordination structure in FeNi-NC@MWCNT. Notably, the Fe Kedge curve of FeNi-NC@MWCNT shows a major peak at 1.9 Å for Fe-Ni scattering, which is different from the peak referred to Fe-Fe interactions for Fe foil at 2.2 Å, indicating no iron metal nanoclusters in the catalyst. For the Ni K-edge FT-EXAFS, the main peak at 1.4 Å for FeNi-NC@MWCNT is comparable to the peak in NiPc curve representing the Ni-Nx coordination structure, which is distinctive to the peaks at 1.6 Å for Ni-O (NiO) and 2.2 Å for Ni-Ni (Ni foil) (Figure ). Moreover, the peak at ~1.8 Å for the Ni K-edge EXAFS data of FeNi-NC@MWCNT can be assigned to Ni-Fe interactions. Besides, the formation of metal-Nx (Fe-Nx, Ni-Nx) coordination in FeNi-NC@MWCNT is further confirmed by Wavelet-transform (WT)-EXAFS spectra. Figure presents the radial distance and k-space resolution to recognize the Fe and Ni at the atomic level in FeNi-NC@MWCNT catalyst. Compared with Fe foil, the location of the intensity maxima of FeNi-NC@MWCNT shows left-shift and down-shift in the bond length R and wave vector k respectively, suggesting the Fe atoms are atomically dispersed into the catalyst in the form of Fe-N coordination. The WT contour plot for FeNi-NC@MWCNT also exhibits a maximum intensity at 6.5 Å -1 in k space, considerably lower that than of Ni foil (7.5 Å -1 ), indicating the atomic dispersion of Ni and the formation of Ni-N bonds in FeNi-NC@MWCNT. The XANES, FT-EXAFS and WT-EXAFS results all suggest that the bulk of in FeNi-NC@MWCNT features Fe-Nx, Ni-Nx and FeNi-Nx sites. Also, nonlinear least-squares EXAFS fitting analysis was performed to quantitatively evaluate the local structural parameters for Fe species and Ni species in FeNi-NC@MWCNT. As shown in Table (SI), the coordination numbers of Fe-N, Ni-N and Fe-Ni in FeNi-NC@MWCNT are estimated to be 2.6, 3.5 and 1.5 (average value) respectively, indicating the formation of Fe-Ni interactions in FeNi-NC@MWCNT. Furthermore, FT-EXAFS k-edge curves of Fe and Ni are both in agreement with the fitting curves simulated from the proposed structural model (SI, Figure and Figure ), suggesting FeNi-N6 sites as a dominant feature in FeNi-NC@MWCNT.