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Protonic ceramic electrochemical cells hold the promise to be operated below 600 o C 1,2 . Although the high proton conductivity of the bulk electrolyte has been demonstrated, it cannot be fully utilized in electrochemical full cells due to unknown causes 3 . Here we showed that it all comes from poor contacts between the low-temperature processed oxygen electrode-electrolyte interface.We demonstrated that a simple acid treatment can effectively rejuvenate the high-temperature annealed electrolyte surface, resulting in reactive bonding between the oxygen electrode and the electrolyte and improved electrochemical performance and stability. This enables exceptional protonic ceramic fuel-cell performance down to 350 o C, with peak power densities of 1.6 W cm −2 at 600 o C, 650 mW cm −2 at 450 o C, and 300 mW cm −2 at 350 o C, as well as stable electrolysis operations with current densities above 3.9 A cm −2 at 1.4 V and 600 o C. Our work highlights the critical role of interfacial engineering in ceramic electrochemical devices and offers new understanding and practices towards sustainable energy infrastructure.

Catalytic hydroboration of alkenes is a wellestablished method to access borane-functionalized hydrocarbons. While linear-selective hydroboration was predominantly reported, catalysts enabling opposite selectivity (branched-selective) are attracting considerable interest, especially when Earth-abundant metals are utilized. This Synopsis summarizes recent progress in Earth-abundantmetal-catalyzed, branched-selective hydroboration of alkenes while overviewing the historical contributions to this reaction using precious metals. Lessons learned from the current state of this topic that can guide future catalyst design are presented, along with challenging issues that remain to be addressed.