Synthesis of Amorphous/Crystalline Heterophase Metal Nanomaterials for Catalysis

Metal nanomaterials have drawn tremendous attention due to their compelling properties and a broad range of applications, especially in catalysis. Recently, phase engineering of nanomaterials (PEN) paves a promising way to modulate the functions and boost the catalytic performances of metal nanomaterials. Besides the crystalline phase, amorphous metal nanostructures showing long-range atomic disordering might also possess distinct properties and show promising applications. In particular, the abundant defects in amorphous metal nanomaterials, e.g., dangling bonds and unsaturated sites, endow them with superior performance in catalytic reactions as compared to the crystalline ones. For example, my group has demonstrated that the amorphization of Pd nanocrystals can dramatically enhance their performance in the electrochemical hydrogen evolution reaction (HER). As known, PEN mainly focuses on the study of nanomaterials with single phase, either crystal phase or amorphous phase. Similar to heterostructures constructed with different components, a heterophase consisting of crystal phase and amorphous phase, i.e., amorphous/crystalline heterophase nanostructure, could exhibit excellent performance in various applications due to the synergistic effect between different phases and the presence of phase boundaries. Recently, for the first time, by using a one-pot wet-chemical method, we have successfully synthesized the amorphous/crystalline heterophase Pd nanosheets with controlled crystallinity. Importantly, it is found that the crystallinity of the Pd nanosheets plays a critical role in the catalytic activity and selectivity in the 4-nitrostyrene hydrogenation. However, it still remains challenges to prepare other amorphous/crystalline heterophase metal nanomaterials with unique properties and promising applications by wet-chemical methods due to the thermodynamically unstable nature of amorphous phase. The promising catalytic performance of aforementioned amorphous/crystalline heterophase Pd nanosheets motivates us to further develop efficient methods for preparing various kinds of amorphous/crystalline metal nanomaterials, including monometallic nanomaterials, metallic nanoalloys, and heterostructured nanomaterials (e.g., core-shell structure, Janus structure, and branched structure). After preparation of the proposed heterophase nanomaterials, we will study their properties and catalytic applications, including electrochemical catalysis (e.g., HER, CO2reduction reaction, etc.) and heterogeneous catalysis (e.g., selective hydrogenation reaction). Moreover, we will investigate the mechanisms for the formation of heterophases and the heterophase-dependent applications.