Molecular Engineering of Metal–Organic Frameworks as Efficient Electrochemical Catalysts for Water Oxidation

Abstract

Metal-organic framework (MOF) solids with their variable functionalities are relevant for energy conversion technologies. However, the development of electroactive and stable MOFs for electrocatalysis still faces challenges. Here, a molecularly engineered MOF system featuring a 2D coordination network based on mercaptan-metal links (e.g., nickel, as for Ni(DMBD)-MOF) is designed. The crystal structure is solved from microcrystals by a continuous-rotation electron diffraction (cRED) technique. Computational results indicate a metallic electronic structure of Ni(DMBD)-MOF due to the Ni-S coordination, highlighting the effective design of the thiol ligand for enhancing electroconductivity. Additionally, both experimental and theoretical studies indicate that (DMBD)-MOF offers advantages in the electrocatalytic oxygen evolution reaction (OER) over non-thiol (e.g., 1,4-benzene dicarboxylic acid) analog (BDC)-MOF, because it poses fewer energy barriers during the rate-limiting *O intermediate formation step. Iron-substituted NiFe(DMBD)-MOF achieves a current density of 100 mA cm −2 at a small overpotential of 280 mV, indicating a new MOF platform for efficient OER catalysis.

Tailoring Metal–Organic Frameworks and Derived Materials for High-Performance Zinc–Air and Alkaline Batteries

“…Figure S4 displays the XRD pattern of the Ni-MOF that consists of very sharp peaks and relatively high crystallinity, providing evidence for the successful formation of the Ni-MOF. The observed pattern (Figure S4) matches perfectly with the simulated pattern of the Ni-BDC (BDC = 1,4-benzenedicarboxylate) MOF (CCDC: 638866). − The diffraction peaks of the as-synthesized LDH, located at 2θ values of 11.61, 22.88, 33.45, and 34.82° are indexed to the (003), (006), (009), and (012) plane reflections, respectively, which are in accordance with the patterns of the hydrotalcite-like materials (Figure S4). In addition, the doublet diffraction peaks located at the 2θ value of ∼60°, corresponding to the Miller indices of (110) and (113), are characteristic peaks of the LDH structures and confirm the appropriate synthesis of LDH. ,, The presence of all of the diffraction peaks related to MOF and LDH in the XRD pattern of the MOF-LDH nanocomposite demonstrates the coexistence of the MOF and LDH structures in the synthesized nanocomposite.…”

Enlarging the Ni–O Bond Polarizability in a Phosphorene-Hosted Metal–Organic Framework for Boosted Water Oxidation Electrocatalysis

“…The comparison of d-band structures (Figure S6) indicates an upshift of the d-band center of NiMOF/BP against NiMOF, which is beneficial for the oxygenated intermediates’ (e . g., O*, OH*, and OOH*) adsorption on the NiMOF/BP surface . The interfacial-plane-averaged electron density difference of NiMOF/BP is further demonstrated in Figure d.…”

“…Electrocatalytic splitting of water (ESW) holds promise for fossil-free hydrogen production toward a future low-carbon society. − The entire ESW process is mainly rate-determined by the sluggish oxygen evolution reaction (OER) at the anode side. − A nonprecious catalyst that can accelerate the OER kinetics is anticipated for the sustainable utilization of the ESW technique. , From Sabatier’s adsorbate evolution mechanism (AEM), ideal OER electrocatalysts are supposed to balance the stepwise interaction intensities with oxygen intermediates (*OH → *O → *OOH → O 2 ). , Under the AEM frame, the thermodynamic energetic scaling relationship (Δ G *OOH – Δ G *OH ≈ 3.2 eV) was developed for the concise computational catalyst design . According to this AEM OER scaling relation, the theoretical overpotential will be valued and minimized at 370 mV, which is still unenergetic for practical OER implementation. , The OER electrocatalyst upgrade should be scheduled along the way to break the scaling relation .…”

Efficient Solar-Driven Water Splitting Enabled by Perovskite Photovoltaics and a Halogen-Modulated Metal–Organic Framework Electrocatalyst

“…The Fourier-transformed (FT) k -weighted extended X-ray absorption fine structure (EXAFS) spectra of Ni at R space and their fitting curves showed no signals corresponding to the Ni–Ni bond at 2.18 Å in Ni-BDC and Ni-TFBDC, indicating a MOF structure (Figure d, Figure S3). Moreover, the positively shifted peak for Ni–O in Ni-TFBDC indicates a longer length after introducing fluorine.…”

“…Lower transition valence states contribute to the generation of the active Ni-OOH species for electrocatalytic OER, leading to better performance. 19,29,30 Thus, the Ni sites in Ni-TFBDC have intrinsic catalytic activities higher than those in Ni-BDC.…”