Enhancing the electrocatalytic potential of trimetallic CeSmGd-MOFs for oxygen evolution reaction, supercapacitor,...

Developing multifunctional materials exhibiting high electrocatalytic activity, superior energy storage capability, and excellent pollutant degradation efficiency is highly desirable for advancing sustainable energy and environmental technologies. A novel approach to fabricate two different trimetallic metal-organic frameworks by a solvothermal method was developed. The synergistic effect of cerium, samarium, and gadolinium with two different organic ligands, namely, 2-NH₂-1,4-benzene dicarboxylic acid and 2,6-naphthalene dicarboxylic acid, was assessed. The rod-like MOFs were further investigated by electrochemical analysis for applications in the oxygen evolution reaction (OER), supercapacitors, and Congo red dye degradation. For the OER, the CeSmGd-NDCA-MOF and CeSmGd-NH₂-BDC-MOF exhibited overpotentials of 188 and 214 mV, respectively, along with Tafel slopes of 57 and 61 mV dec^-1, respectively, at a current density of 10 mA cm^-2. The enhanced electrocatalytic OER performance of the CeSmGd-NDCA-MOF was attributed to its high electrochemical surface area of 1837.5 cm², resulting in a low charge transfer resistance of 2.94 Ω cm^-2 and an enhanced conductivity of 2.04 Ω^-1 cm^-1. Furthermore, supercapattery analysis of the CeSmGd-NDCA-MOF and CeSmGd-NH₂-BDC-MOF revealed that the former exhibited better activity, with a specific capacitance of 697.8 F g^-1 at a scan rate of 5 mV s^-1 and 771.4 F g^-1 at a current density of 1 A g^-1, as calculated from CV and GCD, respectively, in 1 M KOH. A CeSmGd-NDCA-MOF-based two-electrode device was fabricated, and it delivered an energy density of 11.65 Wh kg^-1 and a power density of 500 W kg^-1 at 1 A g^-1. The assembled device revealed a capacitance retention of 94.54% at 100 mV s^-1 and a coulombic efficiency of 100% for 1500 cycles of galvanostatic charge and discharge. For electrochemical CR degradation, the CeSmGd-NDCA-MOF revealed an efficiency of 95.23% at an applied potential of 0.1 V after 25 min (at pH 7, at 14 ppm CR concentration, and in 0.1 M KCl electrolyte) with an energy consumption of 8.89 × 10^-4 kWh m^-3 and an estimated cost of $4.30 × 10^-5.