RESUMO
Direct ethanol fuel cells hold great promise as a power source. However, their commercialization is limited by anode catalysts with insufficient selectivity toward a complete oxidation of ethanol for a high energy density, as well as sluggish catalytic kinetics and low stability. To optimize the catalytic performance, rationally tuning surface structure or interface structure is highly desired. Herein, a facile route is reported to the synthesis of Rh nanosheets-supported tetrahedral Rh nanocrystals (Rh THs/NSs), which possess self-supporting homogeneous interface between Rh tetrahedrons and Rh nanosheets. Due to full leverage of the structural advantages within the given structure and construction of interfaces, the Rh THs/NSs can serve as highly active electro-catalysts with excellent mass activity and selectivity toward ethanol electro-oxidation. The in situ Fourier transform infrared reflection spectroscopy showed the Rh THs/NSs exhibit the highest C1 pathway selectivity of 23.2%, far exceeding that of Rh nanotetrahedra and Rh nanosheets. Density function theory calculations further demonstrated that self-interface between Rh nanosheets and tetrahedra is beneficial for C-C bond cleavage of ethanol. Meanwhile, the self-supporting of 2D nanosheets greatly enhance the stability of tetrahedra, which improves the catalytic stability.
RESUMO
Proton-exchange membrane fuel cells are considered as promising energy-conversion devices. Alloying 3d transition metals with noble metals not only highly improves the performance of noble metal-based catalysts towards electrocatalytic reactions in fuel cells due to d-d hybridization interaction but also decreases the total cost. However, the rapid leaching of transition metal atoms leads to a fast decay of the activity, which seriously affects the performance of the fuel cell. Herein, alloyed Pd-main group metal (e.g. Pb, Bi, Sn) ultrathin nanowires were realized by a facile one-step wet-chemical strategy. The content of the main group metal could be tuned in a certain range while maintaining the same one-dimensional ultrathin nanowire morphology, which provided a large surface area and many more active sites. These Pd-based alloys showed a significant improvement in electrocatalytic activity and durability towards the oxygen reaction reaction as well as ethanol oxidation reaction. Optimal activity occurred when a small amount of main group metal existed, which could be explained through calculations by a strong p-d hybridization interaction between the main group metal and Pd to optimize the surface electronic structure collaboratively. Besides, high stability was achieved, which could be ascribed to the increased antioxidant activity of Pd by the main group metal. Furthermore, the low amount of the main group metal atoms also prevented them from leaching out of the crystal lattice.
