Jiaoe Dang,Sining Yun,Yongwei Zhang,Jingjing Yang,Zhuolei Liu,Changwei Dang,Yinhao Wang,Yingying Deng
With the increasing energy demands and impending climate change, significant concerns have been raised over the metal–organic frameworks (MOFs)-derived porous carbons and their utilization for hydrogen evolution reaction (HER) and triiodide reduction reaction (IRR). However, the provision of high intrinsic activity, active-site accessibility, and structural stability of MOF-derived Co-embedded N-doped carbon (Co/N-C) for HER and IRR is challenging. In this work, core-shell MOF-in-MOF precursors are designed to construct novel double-shell N-C-in-Co/N-C electrocatalysts with nanorod- and rhombic dodecahedron-shaped hollow morphologies (NR-H-C and RD-H-C). The double-shell structured NR-H-C and RD-H-C significantly enhance the HER and IRR activity of Co-MOF-derived Co/N-C. Specifically, NR-H-C achieves a high N-content (10.35 at.%), large specific surface area (590.87 m 2 g −1 ), and hierarchical porous configuration (micropores and mesopores). When NR-H-C is applied as the HER catalyst in alkaline electrolyte, it exhibits an admired overpotential of 123 mV at 10 mA cm −2 and a Tafel slope of 51 mV dec −1 . The solar cell adopting NR-H-C as counter electrode for IRR achieves a high short circuit current density of 16.77 mA cm −2 , an open-circuit voltage of 0.745 V, a fill factor of 0.682, and a power conversion efficiency of 8.51%, higher than that of Pt-based solar cell (16.26 mA cm −2 , 0.744 V, 0.602, and 7.28%). The elucidatory Volmer-Heyrovsky HER mechanism and reversed Volmer-Heyrovsky IRR mechanism give a better understanding of the enhanced dual-functional activity of NR-H-C. This work provides an essential information for the rational design of high-performance dual-functional HER and IRR catalysts and further open up a new avenue for the construction of multicomponent MOFs in the energy conversion field.
Extra-large-pore aluminogermanosilicate zeolite IRR with interconnected 18 × 12 × 12-ring channels was prepared within a wide range of Si/Ge and Al/(Si+Ge) ratio by using a new simple and commercial alkyl-immidazolium as template. The physicochemical properties of IRR zeolite were further characterized by the combination of several techniques, including XRD, SEM, NMR, TGA, ICP, N 2 physisorption, NH 3 -TPD etc. The results revealed that aluminum could be mostly incorporated in the framework with an obviously higher content as a result of the relatively smaller organic template used in this approach. The detemplated IRR by calcination at 550 °C in air presented excellent microporosity with the presence of 18-ring extra-large-pore opening, and considerable amount of acid sites with strong acidity. Finally, for the first time the catalytic performance of IRR zeolite, in comparison with large-pore Beta (12 × 12 × 12-ring) and extra-large-pore NUD-1 (18 × 12 × 12-ring) zeolites, were evaluated for acetalization reaction of aldehydes with triethyl ortoformate. The results showed that the catalytic activity of these three zeolites for aldehydes with different molecular size, that is heptanal and diphenylacetaldehyde, were in diametrically opposite order. IRR exhibited the highest catalytic conversion on bulky substrate diphenylacetaldehyde because its much more open channel system better facilitated the diffusion of reactants into the structure interior, where active acidic sites were located.
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