Rationally Reconstructed Metal–Organic Frameworks as Robust Oxygen Evolution Electrocatalysts

Abstract

Although the metal-organic framework (MOF) based materials have become one of the most important types of electrocatalysts for the sluggish oxygen evolution reaction (OER), a novel design strategy for the MOF structure is highly needed to overcome the current development bottleneck of the electrochemical performance. Reconstructing MOFs towards a designed framework structure provides breakthrough opportunities to achieve unprecedented OER electrocatalytic performance, but has rarely, if ever, been proposed and investigated yet due to the signi cant challenges during the synthesis. Here, we report the rst successful fabrication of a robust OER electrocatalyst by precision reconstruction of an MOF structure from MOF-74-Fe to MIL-53(Fe)-2OH with different coordination environments at the active sites.Theoretical calculations have revealed that the Fe sites in MIL-53(Fe)-2OH with uncoordinated phenolic hydroxyls are more electroactive than that in MOF-74-Fe. Bene ting from this desired electronic structure, the designed MIL-53(Fe)-2OH catalyst exhibits unprecedentedly high intrinsic OER activity, including a low overpotential of 215 mV at 10 mA cm−2, low Tafel slope of 45.4 mV dec−1 and high turnover frequency (TOF) of 1.44 s−1 at the overpotential of 300 mV, which is 81 times higher than the TOF of the commercial IrO2 catalyst (0.0177 s−1). The radically reduced eg-t2g crystal eld splitting in Fe-3d and thus the much suppressed electron hopping barriers through the synergistic effects of the O species from the coordinated carboxyl groups and the uncoordinated phenolic groups guarantee the e cient OER in MIL-53(Fe)-2OH. Consistent with the DFT calculations, the real-time kinetic simulation reveals that the conversion from O* to OOH* is the rate-determining step on the active sites of MIL-53(Fe)-2OH. This work establishes a MOF platform to systematically investigate the structure-property relationship for rationally designing and fabricating robust OER electrocatalysts in the future.

Collaborative Interface Optimization Strategy Guided Ultrafine RuCo and MXene Heterostructure Electrocatalysts for Efficient Overall Water Splitting

“…As demonstrated in Figure h, the C dl value of MXene@RuCo NPs is determined to be 35.01 mF·cm –2 , which is much higher than those of other catalysts. Figure S41 and Tables S5–S8 show the turnover frequency (TOF) and mass activity values of the catalysts, MXene@RuCo NPs exhibit great activity of unit catalytic sites or unit mass for both the HER and the OER Figure i shows the LSV polarization curves of the MXene@RuCo NPs electrode before and after 1000 CV cycles; it has only a small amount of attenuation after CV cycles, which indicates its robust stability for both the HER and the OER.…”

“…Figure S41 or unit mass for both the HER and the OER. 36 Figure 4i shows the LSV polarization curves of the MXene@RuCo NPs electrode before and after 1000 CV cycles; it has only a small amount of attenuation after CV cycles, which indicates its robust stability for both the HER and the OER. The longterm chronopotentiometry test also verifies its robust stability (Figure S42).…”

Defect engineering of two-dimensional materials for advanced energy conversion and storage

“…Up to now, the OER catalytic ability has been generally believed to be mainly related to intermediate adsorption/desorption and their interactions with catalysts. [272][273][274][275] Restricted to a series of consecutive chemical reactions, the OER tends to be kinetically sluggish. It usually needs to overcome large energy barriers for the sophisticated processes, including the multiple electron transfer, the breaking of O-H bonds, and the formation of energy-intensive O-O bonds.…”

Recent progress in metal–organic frameworks (MOFs) for electrocatalysis

“…68 Yuan et al used in situ FT-IR spectroscopy to probe the NRR process of N,B-PC following the associative mechanism. 69 Recently, Yang's group chose to reconfigure the original structure of MOFs to achieve control over monometallic Fe-MOFs, 70 achieving excellent OER activity and stability. Specifically, a precise conversion from phenolic hydroxylligated MOF-74-Fe with hexagonal channels to unliganded MIL-53(Fe)-2OH with rhombic channels was achieved using an in situ solvothermal method (Fig.…”