Engineering the interfacial orientation of MoS 2 /Co 9 S 8 bidirectional catalysts with highly exposed active sites for reversible Li-CO 2 batteries.

Sluggish CO reduction reaction (CORR) and evolution reaction (COER) kinetics at cathodes seriously hamper the applications of Li-CO batteries, which have attracted vast attention as one kind of promising carbon-neutral technology. Two-dimensional transition metal dichalcogenides (TMDs) have shown great potential as the bidirectional catalysts for CO redox, but how to achieve a high exposure of dual active sites of TMDs with CORR/COER activities remains a challenge. Herein, a bidirectional catalyst that vertically growing MoS on CoS supported by carbon paper (V-MoS/CoS@CP) has been designed with abundant edge as active sites for both CORR and COER, improves the interfacial conductivity, and modulates the electron transportation pathway along the basal planes. As evidenced by the outstanding energy efficiency of 81.2% and ultra-small voltage gap of 0.68 V at 20 μA cm, Li-CO batteries with V-MoS/CoS@CP show superior performance compared with horizontally growing MoS on CoS (H-MoS/CoS@CP), MoS@CP, and CoS@CP. Density functional theory calculations help reveal the relationship between performance and structure and demonstrate the synergistic effect between MoS edge sites and CoS. This work provides an avenue to understand and realize rationally designed electronic contact of TMDs with specified crystal facets, but more importantly, provides a feasible guide for the design of high-performance cathodic catalyst materials in Li-CO batteries.