Ultrathin Octahedral CuPt Nanocages Obtained by Facet Transformation from Rhombic Dodecahedral Core–Shell Nanocrystals

Abstract

Copper is an earth-abundant element that can be used to reduce the high cost and unsatisfactory durability of pure Pt catalysts by the formation of bimetallic Pt–M nanocrystals. Among CuPt nanostructures, nanocages attract great interest for catalysis as they allow passage of reactant species to their porous interiors, which provide a high fraction of surface sites. They may also enhance reactivity through an increase in collision frequency by enclosing reagents within nanoscale cavities and by lattice strain effects of the alloy. Recent reports apply solvothermal chemistry to obtain CuPt nanocages in one step. However, there is still a lack of understanding in the formation mechanism and its impact on catalytic activity for such hollow CuPt nanostructures. In this work, we adopt a two-step method in which we synthesize rhombic dodecahedral (RD) Cu–CuPt core–shell nanocrystals by the deposition of Pt on Cu nanocubes to form CuPt shells less than 2 nm in thickness, followed by removing Cu cores to obtain ultrathin octahedral (OCT) nanocages for catalytic applications. By adjustment to shorter and longer reaction time frames, the core–shell nanocrystals were also made into quasi-RD (QRD) and spiny-RD (SRD) morphologies, which lead to porous (POCT) and spiny (SOCT) OCT nanocages, respectively, upon etching. These three types of CuPt nanocages (POCT, OCT, and SOCT) were then examined in the electrocatalytic oxygen reduction reaction (ORR) and the hydrogen evolution reaction (HER) by the hydrolysis of NH3BH3 to study their performance. As a result, the SOCT CuPt nanocages exhibit the highest Pt mass activity (0.3 A/mgPt) in the ORR, a 3-fold improvement over commercial Pt/C. They also show the lowest activation energy (24.3 kJ/mol) in the HER that is better than the commercial catalyst by a factor of 4. HER photocatalysis results show that the POCT and OCT nanocages have localized surface plasmon resonance (LSPR)-enhancement while the SOCT nanocages do not, which is attributed to inhomogeneity in Cu–Pt distributions at shorter reaction times.

Enhancement of NH3 Production in Electrochemical N2 Reduction by the Cu-Rich Inner Surfaces of Beveled CuAu Nanoboxes

“…28 All possible elementary steps were examined by DFT, and the details were provided in Figures 5 and 6 LSPR-Enhanced N 2 RR by CuAu HNBs. Referring to our former work, 6 we expect the heterogeneous distributions of Cu and Au atoms in CuAu HNBs may lead to the existence of nanosized crystal domains that exhibit the localized surface plasmon resonance (LSPR). This suggests the HNBs may have potential as photocatalysts with the ability to harvest light energy for enhancing the catalytic efficiency as in the case of CuRu nanocrystals.…”

“…In this work, we establish that Cu-rich inner walls formed inside CuAu nanoboxes improve the NH 3 Faradaic efficiency in N 2 RR. The hollow CuAu nanobox synthesis was developed via inspiration from previous work with CuPt nanoboxes . Co-reduction of Au 3+ and Cu + ions onto Cu nanocubes led to the formation of beveled Cu-CuAu nanocubes with large CuAu(100) faces.…”

“…The hollow CuAu nanobox synthesis was developed via inspiration from previous work with CuPt nanoboxes. 6 Coreduction of Au 3+ and Cu + ions onto Cu nanocubes led to the formation of beveled Cu-CuAu nanocubes with large CuAu(100) faces. After removing Cu cores by nitric acid etching, hollow CuAu nanoboxes mixed with normal and concave beveled nanoboxes were obtained.…”

Temperature-Induced Variations in Photocatalyst Properties and Photocatalytic Hydrogen Evolution: Differences in UV, Visible, and Infrared Radiation

“…Based on this observation, we propose the following explanation. As displayed in Scheme , under the full spectrum, some Pt NPs will produce a strong SPR effect after absorbing UV light. − The produced hot electrons are either injected into g-C 3 N 4 , or combined with H + to generate 1/2H 2 , − thereby leaving a positive charge on the surface of Pt NPs. Some other Pt NPs do not have a plasmon resonance effect but acquire photoelectrons from g-C 3 N 4 so that the surface of these Pt NPs is negatively charged. − Then, the positively charged and negatively charged Pt NPs will attract each other, thus accelerating the process of thermal agglomeration.…”

PtPd Nanonets Derived from Pd@PtPd RDs as High-Performance Catalysts for the Oxygen Reduction Reaction

“…16 A lot of research studies focused on the special morphologies have been devoted to strengthen the catalysts' activities and stabilities. Through the precise designs, various morphologies have been synthesized, such as nanocages, 17 nanowires, 18 nanoframes, 19 core−shell structures, 20 and so on. Among them, nanoframes have the greatest developing prospect owing to the maximal utilization of active sites.…”