Sublimation‐Vapor Phase Pseudomorphic Transformation of Template‐Directed MOFs for Efficient Oxygen Evolution Reaction

Abstract

Using vapor phase transformation to synthesize template‐directed metal–organic frameworks (MOFs) shows great promise as an approach to avoid the shortcomings of solution‐based strategies. However, among current research, either the products are confined to zeolitic imidazolate frameworks or the conversion technologies are limited to complex processes such as chemical vapor deposition. Here, a well‐designed sublimation‐vapor phase pseudomorphic transformation method is reported to fabricate vertically aligned nanosheet arrays of NiFe‐based MOFs with a uniform and controlled thickness, derived from NiFe‐layered double hydroxides. Benefiting from the optimized morphology and the high intrinsic activity originating from the synergistic coupling effect of NiFe metal clusters, the as‐prepared MOF electrocatalyst displays a superior oxygen evolution reaction performance, requiring an overpotential of 318 mV at 50 mA cm−2 with a Tafel slope of only 47 mV dec−1. Furthermore, a string of metal oxide‐MOFs are obtained, demonstrating the universality of this strategy. By observing the different stages of transformation, the transformation and growth mechanism of MOF crystals is unveiled for the first time. These findings may inspire the exploration and preparation of more species of MOFs, further broadening their application areas.

Etching‐Doping Sedimentation Equilibrium Strategy: Accelerating Kinetics on Hollow Rh‐Doped CoFe‐Layered Double Hydroxides for Water Splitting

“…[52] The cyclic voltammetry (CV) method was utilized to calculate the electrochemical double-layer capacitance (C dl ) to reflect the electrochemical active area (ECSA). [53] As demonstrated in Figure 3d and Figure S15a in the Supporting Information, Rhdoped CoFe-ZLDH has the largest C dl of 33.8 mF cm −2 , which is much higher than that of Rh-doped CoFe-LDH (7.62 mF cm −2 ), CoFe-ZLDH (0.71 mF cm −2 ), CoFe-LDH (0.5 mF cm −2 ), and NF (0.44 mF cm −2 ), as calculated based on corresponding CV curves ( Figure S16, Supporting Information). These results further demonstrate that the samples synthesized by EDSE exhibit higher active area and more active sites than the samples synthesized by the hydrothermal method, which originates from the typical hollow hierarchical structure.…”

“…The smallest radius of Rh-doped CoFe-ZLDH matches the fastest electron transfer kinetics, which is helpful for boosting HER performance (Figure 3e). [53] As shown in Figure S18 in the Supporting Information, the impedance of different Rh feeding content samples was also investigated. Increasing the ratio Rh up to 20% would reduce the impedance.…”

Strong Electronic Interaction Enhanced Electrocatalysis of Metal Sulfide Clusters Embedded Metal–Organic Framework Ultrathin Nanosheets toward Highly Efficient Overall Water Splitting

“…In this regard, MOFs in the form of 2D ultrathin nanosheets are highly desirable and have been successfully developed by ultrasonication-assisted exfoliation, liquidliquid interfacial growth, organic ligand confined synthesis, sublimation-vapor phase transformation, epitaxial growth, sacrificial template growth, and exhibited impressive electrocatalytic performances. [26][27][28][29][30][31] Introducing heterogeneous species into the pristine MOFs is another brilliant way to boost the electrocatalytic activity of MOFs. The conductivity and electrocatalytic performance of MOFs are enhanced by post-synthesis plasma treatment to generate tiny CuS or CoO x nanoparticles in MOFs.…”

In Situ Growth of Hollow Trimetallic Nanocubes on Nickel Foam for the Electrocatalytic Oxygen Evolution Reaction

“…Prussian blue analogues (PBA) with tunable compositions, open framework, low cost and high specific surface areas have been extensively applied to energy storage and conversion field [23–29] . Especially, their derivatives such as transition metal phosphides, [30–34] sulfides, [35–38] carbides, [39,40] nitrides [41–43] and oxides [44] afford superior electrocatalytic property.…”

“…[18][19][20][21][22] Prussian blue analogues (PBA) with tunable compositions, open framework, low cost and high specific surface areas have been extensively applied to energy storage and conversion field. [23][24][25][26][27][28][29] Especially, their derivatives such as transition metal phosphides, [30][31][32][33][34] sulfides, [35][36][37][38] carbides, [39,40] nitrides [41][42][43] and oxides [44] afford superior electrocatalytic property. However, PBA derivatives-based catalysts were mostly adhered to conductive substrates (such as glassy-carbon electrode and nickel foam) by binder materials (Nafion, Polytetrafloroethylene), thus the catalytic performance and durability are not comparable with that of the electrocatalysts in which active species were grown directly on the conductive substrates.…”