Spontaneous anchoring Cl into α‐Co(OH) 2 as efficient and stable oxygen reduction electrocatalysts for seawater battery

Abstract Seawater battery is an advanced energy storage system that enables conversion of chemical energy to electricity by consuming metals, dissolved oxygen and seawater in anode, cathode and electrolyte, respectively. However, the oxygen reduction reaction (ORR) activity and stability of electrocatalysts can be easily deactivated due to the severe Cl − permeation and corrosion in seawater electrolyte. Herein, we developed a structural buffer engineering strategy by spontaneously anchoring Cl − into α‐Co(OH) 2 as efficient and stable ORR electrocatalysts, in which the ultrathin α‐Co(OH) 2 nanosheets were synthesized using an ultrafast solution high‐temperature shock (SHTS) strategy. The large lattice space (~ 0.8 nm) of layered α‐Co(OH) 2 ensured the spontaneously penetration of Cl − into the lattice structure and replaced part of OH − to form α‐Co(OH) 2− x Cl x . The continuous leaching and compensating of saturated Cl in α‐Co(OH) 2− x Cl x could enhance the Cl − corrosion resistance and modulate electronic structure of Co metallic sites, thus improving the ORR electrocatalytic activity and stability in seawater electrolyte. The α‐Co(OH) 2− x Cl x seawater batteries display superior onset and half‐wave potentials of 0.71 and 0.66 V, respectively, which are much better than the counterparts of α‐Co(OH) 2 and of β‐Co(OH) 2 with no Cl − penetrating and no buffer structure. The α‐Co(OH) 2− x Cl x ‐based seawater batteries display stable open‐circuit potential of 1.69 V and outstanding specific capacity of 1345 mAh·g −1 .