Gd Active Sites Modulating the Intermediate Adsorption\nand Activation in Exfoliated Gadolinium Telluride for Oxygen Evolution\nand Reduction Reactions

This\nstudy reveals the synthesis of gadolinium telluride (Gd<sub>2</sub>Te<sub>3</sub>), a non-noble metal alloy with a two-dimensional\n(2D) morphology, for the oxygen evolution reaction (OER) and oxygen\nreduction reaction (ORR). 2D Gd<sub>2</sub>Te<sub>3</sub> exhibits\npromising electrocatalytic activity for OER with an onset potential\nof 1.335 V vs RHE (η = 105 mV) and an overpotential of 1.459\nV vs RHE (η = 229 mV) at 10 mA/cm<sup>2</sup>, rivalling benchmark\ncatalysts such as IrO<sub>2</sub> and RuO<sub>2</sub>. Gd<sub>2</sub>Te<sub>3</sub> exhibited a large turnover frequency of 3.7 s<sup>–1</sup> (at η = 420 mV) and a mass activity of 18.69\nAg<sup>1–</sup> (at η = 470 mV). The chronoamperometric\ndurability studies revealed a consistent current density (>20 mA\ncm<sup>–2</sup>) for 8 h at 1.65 V, reflecting good electrocatalytic\nstability of the material. The competitive OER activity of 2D Gd<sub>2</sub>Te<sub>3</sub> can be attributed to better valence and conduction\nband edge alignment with water oxidation–reduction levels that\nis also corroborated by density functional theory (DFT) studies. 2D\nGd<sub>2</sub>Te<sub>3</sub> also exhibited good ORR performance exhibiting\nan onset potential of 0.72 V vs RHE at 0.1 mA cm<sup>–2</sup>. The number of electron transfers, calculated from H<sub>2</sub>O<sub>2</sub> percentages between 0.30 and 0.50 V vs RHE, revealed\nthat Gd<sub>2</sub>Te<sub>3</sub> follows the 4e<sup>–</sup> ORR pathway with OH<sup>–</sup> as the major intermediate\nproduct. Using DFT calculations, we further elucidate the role and\nimportance of Gd in stabilizing and destabilizing the intermediates\nthat reduce the overpotentials for both the OER and ORR.