Intercalation Chemistry Awakens Transition Metal Hydroxide for Boosted and Sustained Electrocatalytic Sulfion Oxidation

Abstract Electrocatalytic sulfion oxidation reaction (SOR) is a sustainable approach to treat sulfion‐rich sewage for S recovery. Transition metal hydroxide (TMOH), utilized in various electrocatalysis, yet is clumsy in SOR due to overstrong adsorption toward S‐containing intermediates from unsuitable electronic structure. Herein we report, for the first time, that the SOR performance of TMOH can be awakened by intercalation chemistry. Take Co(OH) 2 as a proof‐of‐concept demonstration, MoO 4 2− intercalated Co(OH) 2 2D nanosheet array is engineered, and presents remarkably enhanced SOR behavior with an ultralow potential of 0.29 V versus RHE to attain 100 mA cm −2 , a record Tafel slope of 27.7 mV dec −1 , and stable operation for 192 h without appreciable deterioration. The experimental and theoretical studies unveil that MoO 4 2− ‐intercalated nanoarray is advantageous for active site exposure, and boosting mass transport with enhanced sulfion enrichment and superhydrophilicity. Impressively, MoO 4 2− intercalation can manipulate electronic structure of Co(OH) 2 with downshift of d‐band center, thereby weakening binding strength with HS − and S 8 , and decreasing the |ΔG s* |, eventually enhancing both activity and stability. Notably, such intercalation wake‐up strategy for the SOR is general and can be extended to other oxometallate intercalated TMOH systems. This contribution provides a new paradigm to evoke TMOH for SOR electrocatalysis via elegant intercalation tactic.