Engineering CoCa diatomic oxygen reduction electrocatalysts for high-performance zinc-air battery

Single-atom catalysts featuring cobalt‑nitrogen‑carbon (Co-NC) active sites possess tunable electronic structures and high atomic utilization, making them highly promising for catalyzing the oxygen reduction reaction (ORR) that powers rechargeable zinc-air batteries (ZABs). However, precisely tuning the electronic structure of Co to construct high-density Co-NC active sites with enhanced ORR activity and stability remains a major challenge. Here, we developed a strategy to introduce an alkaline-earth metal, calcium (Ca), to fabricate a catalyst consisting of CoCa dual atoms anchored on nitrogen-doped carbon (CoCa-NC). This approach reveals strong electronic interaction between Co and Ca, where Ca doping facilitates *OH desorption, promotes the intrinsic stability and the formation of a high density of Co active sites. Consequently, the CoCa-NC catalyst demonstrates superior ORR performance with a half-wave potential (E_1/2) of 0.869 V and only a 9 mV loss after 10,000 cycles, significantly prevailing over the single-atom Co-NC counterpart. Furthermore, ZABs catalyzed by CoCa-NC exhibit an extended charge-discharge lifespan of over 1500 h at 5 mA cm^-2. This work highlights the great potential of alkaline-earth metals in dual-atom catalysts (DACs) and offers a practical route for their rational design.