Pd-Nanoparticles Embedded Metal–Organic Framework-Derived Hierarchical Porous Carbon Nanosheets as Efficient Electrocatalysts for Carbon Monoxide Oxidation in Different Electrolytes

Abstract

Rational synthesis of Co-ZIF-67 metal–organic framework (MOF)-derived carbon-supported metal nanoparticles is essential for various energy and environmental applications; however, their catalytic activity toward carbon monoxide (CO) oxidation in various electrolytes is not yet emphasized. Co-ZIF-67-derived hierarchical porous carbon nanosheet-supported Pd nanocrystals (Pd/ZIF-67/C) were prepared using a simple microwave-irradiation approach followed by carbonization and etching. Mechanistically, during microwave irradiation, triethyleneamine provides abundant reducing gases that promote the formation of Pd nanoparticles/Co-Nx in porous carbon nanosheets with the assistance of ethylene glycol and also form a multimodal pore size. The electrocatalytic CO oxidation activity and stability of Pd/ZIF-67/C outperformed those of commercial Pd/C and Pt/C catalysts by (4.2 and 4.4, 4.0 and 2.7, 3.59 and 2.7) times in 0.1 M HClO4, 0.1 M KOH, and 0.1 M NaHCO3, respectively, due to the catalytic properties of Pd besides the conductivity of Co-Nx active sites and delicate porous structures of ZIF-67. Notably, using Pd/ZIF-67/C results in a higher CO oxidation activity than Pd/C and Pt/C. This study may pave the way for using MOF-supported multi-metallic nanoparticles for CO oxidation electrocatalysis.

Pt-Based Nanostructures for Electrochemical Oxidation of CO: Unveiling the Effect of Shapes and Electrolytes

“…Another possible factor is testing the EIS at the CO oxidation potential of each catalyst, which are all different, so the charge transfer across the electrolyte–electrode interface of each catalyst will not be similar and hence the obtained R s will be different. This is shown in the EIS results, which revealed semicircle lines, but with a smaller diameter for Pt NDs than Pt NCs and Pt/C, due to the morphology effect ( Figure 4 e) in line with elsewhere reports [ 24 , 25 ].…”

“…It can be seen that the reduction currents in N 2 ( Figure 3 a) and CO ( Figure 3 b) saturated electrolytes are not the same, due to the strong binding of CO to Pt results in a low surface coverage of OH which not decrease the accessible active sites but also reduce the oxidative removal of CO oxidation intermediates species and Pt-reduction. This leads to difference between the magnitude of both reduction currents as noticed before during CO oxidation on Pt-based or Pd-based catalysts [ 24 , 25 , 53 , 54 ]. The integrated CO oxidation charges from CV curves of Pt NDs, Pt NCs, and Pt/C in the forward scan are approximately 359.5, 160, and 151 μC, respectively, implying the superior CO ads ability of Pt NDs and Pt NCs than Pt/C.…”

“…The CO Oxid current density of PtPd/CNs nanorods (14.75 mA cm −2 ) was superior to Pt/C (7.32 mA cm −2 ) by 2.01 time and bare CNs (0.63 mA cm −2 ) by 23.41 time beside a lower oxidation/onset potential in 0.1 M KOH electrolyte [ 20 ]. Another solution is to use a supporting material, such as carbon-based materials (i.e., carbon nanotubes, carbon nitride [ 20 , 21 , 22 , 23 ], and metal-organic framework [ 24 , 25 ], supported metals nanoparticles and transition metal oxides (i.e., TiO 2 , Pd/Ti 3 C 2 , PdCu/CN, Fe 2 O 3 , and Ce 2 O 3 ) [ 26 , 27 , 28 , 29 ])), can enhance the CO Oxid performance of Pt-based catalysts [ 17 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. This is attributed to the enhanced electrical conductivity, abundant active sites, and electronic interaction with support, which strengthens the adsorption of reactants and facilitate the desorption of intermediates and products [ 40 , 41 , 42 , 43 , 44 ].…”

Pd/Ni-metal–organic framework-derived porous carbon nanosheets for efficient CO oxidation over a wide pH range

“…Exploring MOF/PC with Pd/Ni-N x active sites tailors the electrolyte-electrode interaction and charge transfer resistance resulting in dissimilar CO oxidation activity and voltammogram features in different electrolytes. [66][67][68]…”

Non-Metal-Doped Porous Carbon Nitride Nanostructures for Photocatalytic Green Hydrogen Production

“… The relatively high overpotential, low current densities, and inferior long-term stability are critical barriers in gCNs for HERs, which cannot meet practical requirements (i.e., current density up to several ambers and durability for several weeks or months). This could be solved using noble metal dopants in the formation of heterojunction structures with porous metal oxynitride [ 165 , 166 ], multimetallic nanocrystals [ 12 , 167 , 168 ], MXenes [ 2 , 169 , 170 , 171 , 172 ], MOF [ 10 , 173 , 174 ], graphene [ 175 ], and graphdiyne [ 176 ] to augment solar light harvesting and charge carrier separation during the HER. The safety of H 2 storage tanks should be considered because in the case of unexpected accidents, the H 2 tank becomes a bomb.…”