Phosphorus Incorporation into Co₉S₈ Nanocages for Highly Efficient Oxygen Evolution Catalysis

The improvement of activity of electrocatalysts lies in the increment of the density of active sites or the enhancement of intrinsic activity of each active site. A common strategy to realize dual active sites is the use of bimetal compound catalysts, where each metal atom contributes one active site. In this work, a new concept is presented to realize dual active sites with tunable electron densities in monometal compound catalysts. Dual Co²⁺ tetrahedral (Co²⁺(T_d)) and Co³⁺ octahedral (Co³⁺(O_h)) coordination active sites are developed and adjustable electron densities on the Co²⁺(T_d) and Co³⁺(O_h) are further achieved by phosphorus incorporation (P-Co₉S₈). The experimental results and density functional theory calculations show that the nonmetal P doping can systematically modulate charge density of Co²⁺(T_d) and Co³⁺(O_h) in P-Co₉S₈ and simultaneously improve the electrical conductivity of Co₉S₈, which substantially enhances oxygen evolution reaction performance of P-Co₉S₈.