The realization and subsequent control of emerging structural and electronic phases in solid materials has significantly enhanced their functionalities, thereby benefiting both fundamental research and practical applications. The grain boundary (GB), as a transitional region within the crystal lattice, exhibits atomic shifts and distinct energy profiles. These unique characteristics offer a promising avenue for the discovery of advanced active catalytic phases for carbon, oxygen, hydrogen, and nitrogen evolution/reduction reactions. However, the challenge lies in isolating and controlling the quantity of grain boundaries in conventional catalysts, which hinders the identification of their functional attributes. In this study, we successfully engineered the (001)/(110), (001)/(111), and (110)/(111) GBs in LaNiO