Enhanced electrocatalytic alcohol oxidation with Ni-MOF for direct alcohol fuel cell applications.

The application of MOFs in electrochemical energy fields has attracted great attention in recent years. In this regard, Ni-MOF was synthesized via a solvothermal method using 1,4-benzene dicarboxylic acid (H 2 BDC) as a linker. XRD confirmed the structure of the synthesized Ni-MOF as [Ni 3 (OH) 2 (H 2 O) 4 (C 8 H 4 O 4) 2 ] 2H 2 O. Its porous nature and specific surface area of 82.7 m2 g⁻1 were estimated using BET analysis. Thermal stability was evaluated by TGA, allowing for the calculation of decomposition parameters (E a , ΔH∗, ΔS∗, and ΔG∗). The chemical structure was further validated using FTIR. Ni-MOF powder was blended with carbon black (XC-72) in various ratios to enhance the conductivity and electrocatalytic activity, and the resulting composite was ink-casted onto graphite electrodes. Surface morphology, particle size, and elemental composition were assessed by SEM and EDX, while chemical composition was analyzed through XPS. Notably, the 1:1 Ni-MOF/C composite electrode showed promising catalytic activity for the electrooxidation of methanol, ethanol, ethylene glycol, and glycerol, achieving oxidation current densities of 132, 96, 67, and 57 mA cm⁻2 at +0.8 V (Hg/HgO/OH−), respectively, along with impressive stability. Electrocatalytic performance was further evaluated by calculating electrochemical parameters like diffusion coefficient (D), transfer coefficient (α), catalytic rate constant (K o), Tafel slope, and charge transfer resistance (R ct). The effectiveness of electron transfer processes on Ni-MOF/C relies on the oxidation state of Ni metal ions and the synergistic effect of Ni-MOF and conductive carbon black. EIS results indicated rapid charge transfer processes during alcohol electrooxidation, with the order of efficiency being: methanol > ethanol > ethylene glycol > glycerol. DFT studies investigated the interactions between Ni-MOF crystal facets and alcohol molecules, HOMO−LUMO calculations showed that alcohols possess strong electron donation capabilities, suggesting a favorable affinity for the electrooxidation process. [Display omitted] • Ni-MOF composites with carbon black (XC-72) enhance electrocatalytic activity. • The Ni-MOF: C (1:1) composite exhibited high catalytic activity and durability. • The composite's high performance is due to its porosity and Ni catalytic activity. • DFT revealed that alcohols exhibit strong electron donation abilities. [ABSTRACT FROM AUTHOR]