Improved the Electrocatalytic Hydrogen Evolution Performances of Co-MOF Derivatives Through Introducing Zinc Ions by Two Ways

Abstract

Due to the high price and rareness of precious metal electrocatalysts, the preparation of cheap, high-efficiency nonprecious metal electrocatalysts is urgently needed. In this paper, a Co-metal-organic framework (MOF) has been synthesized by the hydrothermal method. In view of the poor electrocatalytic performance of pristine Co-MOF, we used it as a template and obtained the Co-MOF-800 electrocatalyst by high-temperature calcination at 800 °C under a nitrogen atmosphere. To further improve the electrocatalytic hydrogen evolution performance, we used two methods to synthesize cobalt/zinc bimetallic-based electrocatalysts. The first method is adding zinc ions to Co-MOF and stirring to obtain Co-MOF@Zn; the second method is adding zinc ions during the in situ synthesis to obtain Co/Zn-MOF. Finally, Co-MOF@Zn-800 and Co/Zn-MOF-800 were obtained by pyrolysis at 800 °C under a nitrogen atmosphere. The electrocatalytic hydrogen evolution results show that Co-MOF@Zn-800 and Co/Zn-MOF-800 obtained by doping and introducing zinc ions have larger specific surface areas of 369.837 and 347.898 m2 g–1, respectively, and better electrocatalytic hydrogen evolution performances in 0.5 M sulfuric acid. The overpotentials are 218 and 236 mV at a 10 mA cm–2 current density, and the Tafel slopes are 146.6 and 187.0 mV dec–1. After 40 h of stability testing, the Co-MOF@Zn-800 material still holds a nearly constant current density.

Investigation on the Electrocatalytic Hydrogen Evolution Performance of Coordination Polymer-Derived Materials: Roles of Organic Ligands

“…32 Therefore, we further investigated the field emission transmission electron microscopy (TEM) of Zn/Co-bza-800 and Zn-bza@Co-800, and it can be seen from Figure 5a,b that the metal nanoparticles are uniformly distributed and all wrapped by the carbon; the lattice stripes 0.196 nm corresponded to the Co(111) crystal plane in Zn/Co-bza-800 (Figure 5c) and 0.219 nm corresponded to the Co(111) crystal plane in Znbza@Co-800 (Figure 5d). 33 We found that the crystal plane spacing is different in Zn/Co-bza-800 and Zn-bza@Co-800. 34 Figure 5e shows the distribution of Zn, Co, C, N, and O elements, which also proves the introduction of Co.…”

“…Among them, the structures of Zn/Co-bza-800 and Zn-bza@Co-800 are rougher than that of Zn-bza-800 as can be seen from Figure d,e, indicating that Zn/Co-bza-800 and Zn-bza@Co-800 may provide more active sites than Zn-bza-800 . Therefore, we further investigated the field emission transmission electron microscopy (TEM) of Zn/Co-bza-800 and Zn-bza@Co-800, and it can be seen from Figure a,b that the metal nanoparticles are uniformly distributed and all wrapped by the carbon; the lattice stripes 0.196 nm corresponded to the Co(111) crystal plane in Zn/Co-bza-800 (Figure c) and 0.219 nm corresponded to the Co(111) crystal plane in Zn-bza@Co-800 (Figure d) . We found that the crystal plane spacing is different in Zn/Co-bza-800 and Zn-bza@Co-800 …”

Synthesis of diverse stable MOFs and their electro catalytic capabilities towards desulfurization, water splitting and various nitrophenol reduction reactions

“…Due to its vast surface area, tunable porosity and ability to adapt to various metal centers and ligands, MOFs are regarded as promising electrocatalytic materials. 3,4 The distance that charge carriers must travel to reach the reactants can be greatly reduced when using MOFs with high porosity and accessible surface area in electrocatalysis. To increase both chemical and thermal stability, an organic ligand must covalently bind with different metal ions.…”

“…2,7 To overcome this and to achieve the optimal performance, conductive materials are commonly composited in the MOF derivatives/compositions. 4,5,8 Another strategy is to carbonize the pristine MOFs at a temperature of 500 1C under an inert atmosphere in order to generate MOF-based carbon composites to produce heteroatom-doped porous carbons decorated with metal/metal oxide nanoparticles. In this aspect, it is expected that the carbonized MOFs perform better than the pristine MOF materials.…”

Facile Synthesis of Amorphous NiO/Reduced Graphene Oxide as a Cocatalyst for Enhanced Dye-Sensitized Photocatalytic H2 Evolution

“…Transition metals, especially Ni and its oxides, have been considered as the research topic of non-noble HER cocatalysts due to their abundance, low cost, easy preparation, chemical stability, and high efficiency for HER. − Generally, the cocatalysts are incorporated into some substrates such as graphitic carbon nitride − and various carbon nanomaterials, − which benefit for regulating the structure and morphology of cocatalysts and improving the catalytic activity. For instance, Lu et al reported the NiS x cocatalyst decorated on the graphene (NiS x /G) nanohybrid that exhibited the efficient dye-sensitized photocatalytic HER activity .…”