Modulator-assisted solvothermal synthesis of CeO2 derived from Ce-BDC MOFs: effect on oxygen evolution reaction performance

Abstract

In this study, the morphological, structural, and electrocatalytic properties of Ce-BDC-based metal–organic framework (MOF) materials synthesized under various conditions were comprehensively investigated. Four types of structures Ce-BDC, Ce-BDC-P, Ce-BDC*, and Ce-BDC*-P were prepared using a solvothermal method. The synthesis was carried out both under ambient and pressurized (P) conditions, and with or without acetic acid used as a modulator (*). To optimize the synthesis parameters, the amount of acetic acid (12.5, 25, and 50 Meq) was systematically varied, and among the samples, Ce-BDC*-50-P (synthesized under pressurized conditions with 50 Meq of acetic acid) was identified as exhibiting the highest electrocatalytic performance. Structural characterization was carried out using XRD, FT-IR, SEM–EDS, XPS, and BET analyses, which revealed the influence of synthesis parameters on crystal structure, morphology, and porosity. Electrochemical performance evaluations were conducted in 0.5 M H₂SO₄ solution using a standard three-electrode system. Among the synthesized samples, Ce-BDC*-50-P demonstrated the best oxygen evolution reaction (OER) activity, with a low overpotential of ~ 290 mV and a Tafel slope of 95.7 mV dec⁻¹. Its superior catalytic activity was attributed to a high surface area (164 m² g⁻¹) and a low charge transfer resistance (12.37 Ω·cm²). These findings suggest that the modulator-assisted pressurized synthesis approach significantly enhances the electrocatalytic activity of Ce-MOF materials by promoting their partial transformation into CeO₂ derivatives, thus improving their performance in OER applications.