Nanosized Pd@Ag heterojunction with tunable shapes: Morphological modulation for improving plasma-mediated catalytic hydrogen evolution

Catalytic ability of bi-metal hybrid nanoagents largely depends on their phase constitution and morphology, also bearing a close correlation to the fabrication process. We herein design and develop a modified polyol protocol with inorganic ion induction for rationally constructing Ag nanoagents with tunable shapes (nanowire, nano-cube, and nanoparticle), followed by evenly anchoring of stepwise reduced Pd nanograins on the surface of Ag nanoagents to foster Ag core -Pd shell (i.e. Pd@Ag) nanosized heterostructure. A home-made photochemical reaction device is used to scientifically evaluate the catalytic ability of the Pd@Ag nanoagents on hydrolyzing ammonia borane to evolve hydrogen gas. The ample characterization reveals that the fabricated Ag nanoagents hold the expected regular and uniform shapes, with 10-15 nm thick Pd layer cladded on their surfaces. The particular shapes of the Ag nanoagents can be duly manipulated via the induction of inorganic ions, and the thickness and compactness of the Pd shell can also be suitably regulated by controlling reduction duration. The verified formation of electron synergistic effect among the both metals is favorable to elevate the catalytic ability. The bimetal Pd@Ag nanoagents perform the superior catalytic activity under visible light irradiation, far exceeding that of the respective monometal counterparts, with the order of catalytic activity: Pd@Ag-NWs > Pd@Ag-NCs > Pd@Ag-NPs. The hydrolysis reaction at the given conditions is confirmed to be quasi first-order reaction, with the apparent activation energy of 53.44 kJ & sdot;mol-1 and TOF value of 47.04 min(-1). The Pd@Ag-NWs catalyst behaves satisfactory stability, with 87.8 % initial catalytic activity retained after five cyclic use.