Revealing the Structural Transformation between the Activity and Stability of 2D and 3D Co–Mo Metal–Organic Frameworks for a Highly Active Oxygen Evolution Reaction

Abstract

The development of highly active and cost-effective metal–organic frameworks (MOFs) with large surface areas, abundant active sites, and distinct structures resulted in reduced kinetic barriers involving a four-electron transfer path for the oxygen evolution reaction (OER). In this work, the OER activity of cobalt–molybdenum metal–organic framework (Co-Mo-MOF)-based materials was significantly improved by controlling 3D and 2D framework structures, namely, Co-Mo-3D and Co-Mo-2D, respectively. When Co-Mo-3D was reacted in an alkaline electrolyte, a highly porous gyroid morphology with a large surface area was formed and designated as KOH-treated Co-Mo-3D. The KOH-treated Co-Mo-3D demonstrated superior OER electrocatalytic activity with a low overpotential of 210 mV at a current density of 10 mA cm–2 and small Tafel slope of 50 mV dec–1 in alkaline solution. In addition, KOH-treated Co-Mo-3D exhibited excellent long-term durability at different voltages. The detailed structure transformation of Co-Mo-MOFs during the reaction was also provided by in situ X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), and ex situ X-ray absorption spectroscopy (XAS). Moreover, density functional theory (DFT) calculations revealed that the hydrogen-bonding network system formed in Co-Mo-3D plays an important role in assisting proton transfer and enhancing the catalytic activity of the OER. This work opens up a new prospect for the design and development of catalytically active pillar-layered MOF catalysts for OERs.

Construction of desert rose flower-shaped NiFe LDH-Ni3S2 heterostructures via seawater corrosion engineering for efficient water-urea splitting and seawater utilization

“…3 However, both half-reactions of water electrolysis namely the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) require high-performance bifunctional electrocatalysts to overcome the sluggish kinetics and enhance efficiency. 4 Over recent several decades, a myriad of alternative cost-effective and earth-abundant transition metal-based electrocatalysts (especially Ni, Fe and Co), including alloys, metal oxides, 5 metal hydroxides, 6 and metal–organic frameworks 7 have been exploited to accelerate the half-reaction kinetics. And some of them even outperformed the Pt/C and RuO 2 benchmark catalysts.…”

Modulating the Energy-Band of Metal Oxide@Metal–Organic Framework Core–Shell Nanoparticles for Enhanced Raman Sensing

“…The C 1s region could be fitted by four peaks centered at 283.6, 284.1, 284.8, and 287.8 eV, which could be assigned to CC, C–O, and CO bonds, respectively. Also, the O 1s region could be fitted by three peaks centered at 530.3, 531.2, and 532.3 eV, which could be assigned to Fe–O, Co–O, and CO bonds, respectively. , The characterizations of other core–shell heterostructures are outlined in the Supporting Information (Figures S6–S18).…”

Material Changes in Electrocatalysis: An In Situ/Operando Focus on the Dynamics of Cobalt‐Based Oxygen Reduction and Evolution Catalysts

“…Unlike the Co ZIF‐67, however, from ex situ XRD and TEM, the pristine MOF structure is shown to not be fully lost, suggesting that these changes are limited to the surface of the particles or only impact some particles. Mo and Co K edge XAS on a bimetallic Co−Mo 3D MOF showed subtler changes at 1.5 V vs RHE in 1 M KOH [120] . While Mo is already fully oxidized Mo 6+ as in Na 2 MoO 4 in the pristine MOF, there are subtle changes during OER, with a relative decrease in white line intensity and increase in pre‐edge feature indicating an increase in distortion of the Mo octahedron.…”

“…Mo and Co K edge XAS on a bimetallic CoÀ Mo 3D MOF showed subtler changes at 1.5 V vs RHE in 1 M KOH. [120] While Mo is already fully oxidized Mo 6 + as in Na 2 MoO 4 in the pristine MOF, there are subtle changes during OER, with a relative decrease in white line intensity and increase in pre-edge feature indicating an increase in distortion of the Mo octahedron. Co has a significant increase in oxidation state, resembling Co(OH) 2 , along with increased CoÀ O coordination, but does not reach the Co � 3 + state observed in the other studies.…”