Abstract
Noble metal nanostructures are being used broadly as catalysts for energy conversion in fuel cells. To overcome the future energy crises, fuel cells are anticipated as clean energy sources because they can be operated at low temperature, their energy conversion is high and their carbon release is almost zero. However, an active and stable electrocatalyst is essential for the electrochemical reactions in fuel cells. Therefore, properties of the nanostructures greatly depend on the shape of the nanostructures. Individual as well as interaction properties are greatly affected by changes in the surface area of the nanostructures. By shape controlled synthesis, properties of the nanostructures could be further enhanced by increasing the surface area or active sites for electrocatalysts. Therefore, an efficient approach is needed for the fabrication of nanostructures to increase their efficiency, activity, or durability in fuel cells by reducing the usage of noble metals. Different types of hollow nanostructures until now have been prepared including nanoboxes, nanocages, nanoshells, nanoframes (NFs), etc. NFs are the hollow unique three-dimensional structure which have no walls—they only contain corners or edges so they have large surface area. In electrocatalytic reactions, the molecules involved in the reaction can easily reach the inner surface of the nanoframes, thus noble metals' utilization efficiency increases. NFs usually have high surface area, greater morphological and compositional stabilities, allowing them to withstand harsh environmental conditions. By considering the current challenges in fabrication of noble metal based alloy NFs as electrocatalysts, this review paper will highlight recent progress, design, and fabrication of noble metal alloy NFs through different strategies—mainly photocatalytic template, electrodeposition, Kirkendall effect, galvanic replacement, chemical/oxidative etching, combination of both and other methods. Then, electrochemical applications of NFs in fuel cells toward formic acid, methanol, ethanol, oxygen reduction reaction as well as bifunctional catalyst will also be highlighted. Finally, we will summarize different challenges in the fabrication of highly proficient nanocatalysts for the fuel cells with low cost, high efficiency and high durability, which are the major issues for the highly commercial use of fuel cells in the future.
Highlights
Noble metal nanostructures are being used broadly as catalysts for energy conversion in fuel cells
In case of PtCu alloy, the surface electronic structure of pure platinum was modified and the electrocatalytic properties enhanced toward oxygen reduction reaction because of a drop of adsorption energy between platinum and oxygen species
Pt3Ni tetrahexaherdal NFs were developed by carbon monoxide (CO) etching which is highly open, stable as and has a higher index microstructure which consists of a segregated Pt thin surface and downshifted d-band center, which is revealed by the Density Functional Theory (DFT)
Summary
Noble metal nanostructures are being used broadly as catalysts for energy conversion in fuel cells. Recent research efforts have been focused on (1) the addition of cheap transition metals to decrease the cost and improve the electronic effect of Pt, (2) tuning the morphologies with high index facets, ultrathin walls and 3D surface accessibility, (3) NF architecture which shows the 3D surface with high catalytic surface area as well as large utilization of precious metals, (4) composition segregation of Pt on the edges and corners of NFs to increase the Pt usage. Some groups have been interested in the atomic scale synthesis of bi- and multimetallic NFs due to their excellent electrocatalytic activity as well as durability in fuel cells. Researchers have fabricated the single component noble metal hollow, nanocages and NFs, but few have focused on the fabrication of noble metal based bimetallic and multimetallic NFs for fuel cells
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
