The insights on the primary active oxygen specie and its relation with oxygen vacancy is essential for the design of low-temperature oxidation catalysts. Herein, oxygen vacancy-rich La 0.8 Sr 0.2 CoO 3 with an ordered macroporous structure was integrated on the commercial ceramic monolith in large scale without additional adhesives via a facile in situ solution assembly. The constructed macropores not only contributed to the oxygen vacancy generation in catalyst preparation but also facilitated favorable mass transport during catalytic process. Combined with theoretical investigations and EPR, O 2 -TPD, H 2 -TPR observations, we revealed that monatomic oxygen ions (O − ) are the primary oxygen active specie for perovskite oxide. And molecular O 2 is more favorably adsorbed and activated on surface oxygen vacancies via a one electron transfer process to form monatomic oxygen ions (O − ), thus boosting richness of active O − and the low-temperature oxidation of CO. Different with the preferential Eley−Rideal (E-R) mechanism on pristine LSCO surface, Langmuir−Hinshelwood (L-H) mechanism, in which O − reacts with adsorbed CO to finish the oxidation reaction, was more favorable on the oxygen vacancy rich surface. Our work here elucidates the primary active oxygen specie as well as its origin over perovskite oxides and paves a feasible pathway for rational design of high-performance catalysts in heterogeneous reactions.

High-current density (≥1 A cm–2) is a critical factor for large-scale industrial application of water-splitting electrocatalysts, especially seawater-splitting. However, it still remains a great challenge to reach high-current density due to the lack of active and stable intrinsic catalytic active sites in catalysts. Herein, we report an original three-dimensional self-supporting graphdiyne/molybdenum oxide (GDY/MoO3) material for efficient hydrogen evolution reaction via a rational design of “sp C–O–Mo hybridization” on the interface. The “sp C–O–Mo hybridization” creates new intrinsic catalytic active sites (nonoxygen vacancy sites) and increases the amount of active sites (eight times higher than pure MoO3). The “sp C–O–Mo hybridization” facilitates charge transfer and boosts the dissociation process of H2O molecules, leading to outstanding HER activity with high-current density (>1.2 A cm–2) in alkaline electrolyte and a decent activity and stability in natural seawater. Our results show that high-current density electrocatalysts can be achieved by interfacial chemical bond engineering, three-dimensional structure design, and hydrophilicity optimization.

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