調整鹵素離子開關以控制金鈀奈米二十面體合金與核殼結構的形成及其在催化表現上的探討
Turning the Halide Switch in the Synthesis of Au−Pd Alloy and Core−Shell Nanoicosahedra with Terraced Shells: Performance in Electrochemical and Plasmon-Enhanced CatalysisNano Lett. 2016, 16, 5514−5520
DOI: 10.1021/acs.nanolett.6b02005
金-鈀奈米合金因其出色的異相催化能力和表面電漿共振增強特性而在研究上備受矚目。此種雙金屬結構中，奈米金除了化學耐久度高，更扮演著集取光能量的角色，將光能量轉移至共金屬而增強其催化活性。文獻中指出，奈米二十面體有著高的催化活性，但成長速率影響結構轉變為合金或核殼結構仍為目前的一大挑戰。在本工作，我們發展出可調控結構的一鍋化水相合成法，使得金屬離子共還原的過程中，藉由提高氯或溴離子的相對濃度可分別得到金-鈀合金與核-殼奈米二十面體結構。為了確認奈米二十面體觸媒活性與表面電漿共振增強特性，我們進行乙醇的電化學氧化與對硝基苯酚的光還原反應以為測試，並了解到總是核-殼結構表面出最優越的催化活性。在乙醇電化學氧化反應中，核殼觸媒甚至表現出相當於商用鈀觸媒2.7倍的活性。此外，由於核殼觸媒的核具有高密度的金原子組成，相對合金結構，可產生明顯的表面電漿共振增強特性，因此於對硝基苯酚的光還原反應中，在可見光的激發下，催化活性大幅提升。
Au-Pd nanocrystals are an intriguing system to study the integrated functions of localized surface plasmon resonance (LSPR) and heterogeneous catalysis. Gold is both durable and can harness incident light energy to enhance the catalytic activity of another metal, such as Pd, via the SPR effect in bimetallic nanocrystals. Despite the superior catalytic performance of icosahedral (IH) nanocrystals compared to alternate morphologies, the controlled synthesis of alloy and core-shell IH is still greatly challenged by the disparate reduction rates of metal precursors and lack of continuous epigrowth on multiply-twinned boundaries of such surfaces. Herein, we demonstrate a one-step strategy for the controlled growth of monodisperse Au-Pd alloy and core-shell IH with terraced shells by turning an ionic switch between [Br─ ]/[Cl─ ] in the co-reduction process. The core-shell IH nanocrystals contain AuPd alloy cores and ultra-thin Pd shells (< 2 nm). They not only display more than double the activity of the commercial Pd catalysts in ethanol electrooxidation attributed to terraces, but also show SPR-enhanced conversion of 4-nitrophenol. This strategy holds promise toward the development of alternate bimetallic IH nanocrystals for electrochemical and plasmon-enhanced catalysis..
