Surface atomic modulation of CoP bifunctional catalyst for high performance Li-O₂ battery enabled by high-index (211)...

The rational design of the surface structure and morphology characteristics of the catalyst at atomic level are the key to improve the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in lithium-oxygen (Li-O₂) battery. Here a series of cobalt phosphide (CoP) electrocatalysts with a variety of index facets are successfully prepared including concave polyhedrons CoP exposing with (211) crystal planes (CoP CPHs) spherical nanoparticles CoP exposed with (011) crystal planes and polyhedron particles CoP exposing with (011) and (111) crystal planes. The results show that CoP CPHs based Li-O₂ battery presents a large discharge capacity of 33743 mA h g^-1 at current density of 50 mA g^-1 and a remarkable long cycle life of up to 950 h. The experimental results demonstrates that the CoP CPHs electrode exposing with high-index (211) facets based Li-O₂ battery exhibits an extremely low overpotential (0.67 V) ultrahigh specific capacity (33743 mAh g^-1) and remarkable long-term stability of up to 950 h. Most importantly density functional theory (DFT) calculations demonstrate the excellent electrocatalytic activity of high-index (211) facets as compared to the low-index (011) and (111) planes are because of the existence of large density of atomic steps edge ledge sites and kinks which supply a wide space for breaking chemical bonds and increasing the reaction activity for oxygen electrode.