High‐Performance Overall CO2 Splitting on Hierarchical Structured Cobalt Disulfide with Partially Removed Sulfur Edges

The ability to develop bifunctional electrocatalysts for concurrent CO₂ reduction reaction (CO₂RR) and oxygen evolution reaction (OER) is the key to the practical application of CO₂ splitting to produce CO. However, this remains a grand challenge. Herein, a robust strategy to rationally craft hierarchical structured bifunctional electrocatalysts composed of 3D CoS₂ nanocages interconnected on 2D CoS₂ nanosheet arrays (denoted hierarchical CoS₂ nanocages) for high‐performance CO₂ splitting is developed. The subsequent calcination removes the partial S edges of CoS₂, thereby strongly suppressing the hydrogen evolution reaction (HER) of CoS₂. By combining theoretic and experimental results, for the first time, it is discovered that the plane S of CoS₂, instead of S edges, are highly active for CO₂RR but inactive for HER, rendering the plane S as ideal active sites for CO₂RR. Intriguingly, the composition tuning via calcination and the presence of a hierarchical architecture confer hierarchical CoS₂ nanocages respective outstanding CO₂RR and OER performance. Notably, the hierarchical CoS₂ nanocages can be exploited as bifunctional electrocatalysts for overall CO₂ splitting to yield the current density of 1 mA cm^?2 at a small cell voltage of 1.92 V, much lower than the widely reported values (>2.5 V).