Counting d‐Orbital Vacancies of Transition‐Metal Catalysts for the Sulfur Reduction Reaction

Abstract The electrocatalytic sulfur reduction reaction (SRR) would allow the production of renewable high‐capacity rechargeable lithium‐sulfur (Li‐S) batteries using sustainable and nontoxic elemental sulfur as a cathode material, but its slow reaction rate causes a serious shuttle effect and dramatically reduces the capacity. We found that a catalyst composed of Pd nanoparticles supported by ordered mesoporous carbon (Pd/OMC) had a high reaction rate in the SRR, and a Li‐S battery assembled with this catalyst had a low shuttle constant of 0.031 h −1 and a high‐rate performance with a specific capacity of 1527 mAh g −1 at 0.1 C which is close to the theoretical value. The high activity of Pd/OMC with a d ‐orbital vacancy of 0.87 e was predicted from a volcano relationship between the d charge for the metal and the adsorption activation entropy and reaction rate for the SRR by examining Pd, Au, Pt, Rh, and Ru transition‐metal nanocatalysts. The strategy of using a single electronic structure descriptor to design high‐efficiency SRR catalysts has suggested a way to produce practical Li‐S batteries.