Electrocatalytic oxygen reduction by a Co/Co₃O₄@N-doped carbon composite material derived from the pyrolysis of ZIF-67/poplar flowers

Abstract

Co/Co3O4@NC catalyst for the ORR with a low cost and highly stable performance is developed through the pyrolysis of an easy physical mixture containing ZIF-67 as the precursor and poplar flowers as the carbon source.

Efficient electrocatalytic oxygen reduction reaction of thermally optimized carbon black supported zeolitic imidazolate framework nanocrystals under low-temperature

“…For example, 80ZKB-600 sample ORR activity is even outperforming ZIF-700 by offering more positive E onset (∼0.9 V) and E 1/2 (∼0.82 V) values. Literature data shows that ZIF-67 or relevant MOF or metal-coordinated molecular structures required to carbonise at greater than 700 °C, 1–7,9–12,15–19,22–24,27–34 however, they show inferior ORR activities than the 80ZKB-600 sample; this is linked to significant graphitization of ligand carbon, which become hydrophobic, along with severe agglomeration of Co(0) nanoparticles. For example, ZIF-67 carbonized at 800 °C under 5%H 2 /Ar atmosphere displays inferior E onset , E 1/2 and limiting-current density ( J L ) values of 0.86 V, 0.78 V, and 4.1 mA cm −2 , respectively.…”

“…Numerous design/synthesis routes have been discussed for generating functional electrocatalyst materials. 1–36 Among these, carbothermal synthesis of metal-coordinated small molecular or polymeric networks have shown promising electrocatalytic activities. Pre-synthesized porous networks, such as metal–organic frameworks (MOFs) are often utilised precursors with the choice of enriched metal centres and ligand/linker carbon network with functional heteroatom groups, which can enhance the electrophilicity and heterogeneity of the metal-carbon network and thus promote the adsorption/desorption of reactants/intermediates during the catalytic process.…”

“…Compared to thermolyzed samples of ZIF-67 and KB-controlled, the thermally optimized 60ZKB sample at 600 °C (named 60ZKB-600) exhibited highly improved ORR performance with competitive onset and half-wave potential ( E onset and E 1/2 , respectively) values of ∼0.90 and ∼0.83 V ( vs. RHE), which are comparable or better than many carbon-based Co–N–C and CoO x –N–C or Co@CoO x –N–C electrocatalysts synthesized under higher thermolysis and prolonged chemical modification conditions. 1–24,27–34 Structural and electrochemical characterisations by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV) and linear sweep voltammetry (LSV) of the samples reveal the fine-dispersion of Co@CoO/Co 3 O 4 nanoparticles (∼5 nm size) in N-doped KB support. Thus, results and analysis presented in this work indicate that low-cost and abundantly available carbon black materials can be turned into highly active electrocatalyst materials by surface grown MOFs and their mild carbothermal optimization at or below 600 °C.…”

Porous carbon cubes decorated with cobalt nanoparticles for oxygen evolution catalysis in Zn‐air batteries

“…As shown in Figure 4C, the Raman spectra of the Co@N-PCC samples showed D and G bands at 1351.6 and 1598.5 cm À1 , respectively. 32 The D and G bands indicated defects related to the disordered and graphitic carbon, respectively. The intensity ratio of the D to G bands (I D / I G ) is a measure of the degree of graphitization in carbonaceous materials.…”

Cordierite@MOFs with Easy Recovery in CO2 Cycloaddition

“…The XPS spectra support the existence of Co, N, C, O, Al, Si, and Mg in the cordierite@ZIF-67 catalysts (Figure ). For example, the Al 2p spectrum was deconvoluted into one peak at a binding energy of 73.9 eV, which was assigned to the Al–O group. − From thermogravimetric analysis (TGA), the thermal stability of cordierite@ZIF-67 was confirmed to be as high as 300 °C, as shown in Figure S2. TGA of cordierite@ZIF-67 mainly indicates only one decaying step in the temperature range of 350–400 °C, and the amount of Co was about 1%.…”