Theoretical designs of ORR/OER single‐atom catalysts TM@Ti₂CT₂ (T = O, S, Cl)

AbstractDriven by the goal of establishing a fossil‐fuel‐free and nuclear‐power‐free economy based on renewable energy, metal‐air batteries are regarded as promising energy conversion and storage devices. Developing efficient oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) bifunctional electrocatalysts for the air electrode of metal‐air batteries is becoming increasingly important. In this work, 36 transition metal (TM) single‐atom catalysts are designed based on MXenes Ti2CT2 with different surface terminal atoms (T = O, S, Cl), and their ORR/OER catalytic activity and stability are evaluated by the density functional theory. Ni@Ti2CO2, Pd@Ti2CS2, and Co@Ti2CCl2 are found to exhibit good catalytic activity with ORR/OER overpotentials of .54 V/.62 V, .59 V/.29 V, .44 V/.40 V. The aggregation behavior of three catalysts is estimated by comparing the average binding energy of one, two, three, and four TM atoms anchored on Ti2CT2. This work cannot only provide a theoretical guide to develop bifunctional single‐atom catalysts, but also help us understand the effect of terminal atoms on the electronic structures and catalytic activity of TM@Ti2CT2.