CTAB-templated synthesis and characterization of nanorod-shaped NiCo2O4 crystals for supercapacitor application

Using Magnetometry to Understand the Relative Role of Magnetic Particles in Co-Based Catalysts for the Oxygen Reduction Reaction

“…To further understand the role of CTAB in the precursor synthesis, we synthesized another catalyst material, starting with only Co­(NO 3 ) 2 and CTAB. CTAB has been used previously to assist in the formation of Co-containing nanoparticles. ,, We then mixed the resulting product with XC72 to make the catalyst conductive. Based on fitting of the SQUID magnetometry data (see Calculation S2), the radius of the Co NPs in the Co NPs + XC72 material is 1.57 ± 0.02 nm.…”

“…The addition of CTAB to the precursor mixture leads to an increased percentage of Co in the precursor MOF (Table ) as well as the final catalyst (Table ). CTAB has been used previously to assist in the formation of Co-containing nanoparticles, ,, which may explain its role in the synthesis of CoNC-CTAB.…”

“…Prior to addition of 2-methylimidazole the pH of precursor solution is 3, but the solution exhibits a pH of 5 following 2-methylimidazole addition. Indeed, addition of base is commonly used in CTAB syntheses of Co nanoparticles. , With addition of 2-methylimidazole the solution becomes basic enough to form nanoparticles, competing with the MOF formation. The addition of base is necessary for the formation of Co oxides (likely the form of the metallic Co nanoparticle prior to pyrolysis) because of the metathesis reaction between the Co­(NO 3 ) 2 and base. − The critical micelle concentration (CMC) for CTAB is reported to be between 0.7 and 1 mM. − The concentration of CTAB in the solution for CoNC-CTAB preparation is 27 mM, well above the CMC.…”

“…CTAB has been used previously to assist in the formation of Co-containing nanoparticles. 20,46,47 We then mixed the resulting product with XC72 to make the catalyst conductive. Based on fitting of the SQUID magnetometry data (see Calculation S2), the radius of the Co NPs in the Co NPs + XC72 material is 1.57 ± 0.02 nm.…”

“…Indeed, addition of base is commonly used in CTAB syntheses of Co nanoparticles. 46,47 With addition of 2-methylimidazole the solution becomes basic enough to form nanoparticles, competing with the MOF formation. The addition of base is necessary for the formation of Co oxides (likely the form of the metallic Co nanoparticle prior to pyrolysis) because of the metathesis reaction between the Co(NO 3 ) 2 and base.…”