Transition-metal single atoms embedded into defective BC3 as efficient electrocatalysts for oxygen evolution and reduction reactions

Abstract

Searching for high-activity, stable and low-cost catalysts toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are of significant importance to the development of renewable energy technologies. By using the computational screening method based on the density functional theory (DFT), we have systematically studied a wide range of transition metal (TM) atoms doped a defective BC₃ monolayer (B atom vacancy V_B and C atom vacancy V_C), denoted as TM@V_B and TM@V_C (TM = Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ir and Pt), as efficient single atom catalysts for OER and ORR. The calculated results show that all the considered TM atoms can tightly bind with the defective BC₃ monolayers to prevent the atomically dispersed atoms from clustering. The interaction strength between intermediates (HO*, O* and HOO*) and catalyst govern the catalytic activities of OER and ORR, which has a direct correlation with the d-band center (ε_d) of the TM active site that can be tuned by adjusting TM atoms with various d electron numbers. For TM@V_B catalysts, it was found that the best catalyst for OER is Co@V_B with an overpotential η^OER of 0.43 V, followed by Rh@V_B (η^OER = 0.49 V), while for ORR, Rh@V_B exhibits the lowest overpotential η^ORR of 0.40 V, followed by Pd@V_B (η^ORR = 0.45 V). For TM@V_C catalysts, the best catalyst for OER is Ni@V_C (η^OER = 0.47 V), followed by Pt@V_C (η^OER = 0.53 V), and for ORR, Pd@V_C exhibits the highest activity with η^ORR of 0.45 V. The results suggest that the high activity of the newly predicted well dispersed Rh@V_B SAC is comparable to that of noble metal oxide benchmark catalysts for both OER and ORR. Importantly, Rh@V_B may remain stable against dissolution at pH = 0 condition. The high energy barrier prevents the isolated Rh atom from clustering and ab initio molecule dynamic simulation (AIMD) result suggests that Rh@V_B can remain stable under 300 K, indicating its kinetic stability. Our findings highlight a novel family of efficient and stable SAC based on carbon material, which offer a useful guideline to screen the metal active site for catalyst designation.