Regulating d-orbital electronic configuration of Ni-based chalcogenides to enhance the oxygen electrode reactions in Li-O2 batteries

First Principles Study of the Structure–Performance Relation of Pristine Wn+1Cn and Oxygen-Functionalized Wn+1CnO2 MXenes as Cathode Catalysts for Li-O2 Batteries

“…The overpotential is defined as the minimum that makes all the electrochemical steps downhill in free energy and serves as a crucial indicator for assessing the catalytic performance of a catalyst [ 51 ]. The smaller the value of , the lower the actual voltage required to achieve a target current density, resulting in reduced energy consumption and enhanced catalytic activity [ 45 , 53 ]. In this study, we calculated the ORR ( ), OER ( ), and total ( ) overpotentials by , , and , respectively.…”

“…Among all considered WC MXenes, W 4 C 3 O 2 exhibits the lowest OER, ORR, and total overpotentials (0.38, 0.25, and 0.63 V). Furthermore, it is worth noting that the overpotentials ( , , and ) of W 4 C 3 O 2 are lower than those of Nb 2 CO 2 MXene (0.81, 0.50, and 1.31 V) [ 57 ], Se@NiO/CC (0.32, 0.36, and 0.68 V) [ 58 ], SASe–Ti 3 C 2 (0.59, 0.29, and 0.88 V) [ 59 ], CuCo 2 S 4 (0.35, 0.30, and 0.65 V) [ 60 ], NiSA-Co 3 O 4 (1.09, 0.21, and 1.30 V) [ 12 ], CoS 2 (0.89, 0.47, and 1.36 V) [ 61 ], and other recently reported two-dimensional materials [ 45 , 62 , 63 ]. These suggest that the W 4 C 3 O 2 MXene shows excellent catalytic performance as a cathode catalyst for Li-O 2 batteries.…”

“…The ORR ( ), OER ( ), and total ( ) potentials are defined as , , and , respectively. In this definition, represents the highest discharge potential that drives the energy downhill for all ORR steps, represents the lowest charge potential that drives the energy downhill for all OER steps, and denotes the equilibrium potential ( ) that facilitates the spontaneous occurrence of ORR/OER [ 45 , 46 ].…”