Facet-specific heterojunction in gold-decorated pyramidal silicon for electrochemical hydrogen peroxide sensing
Chia-Wei Huang, Joey Andrew A. Valinton, Yung-Jr Hung, Chun-Hu Chen
Index: 10.1016/j.snb.2018.03.131
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Abstract
Nanoscale heterojunction of asymmetrical band structures and electron distributions at the interfaces is critical for activity enhancement in various catalytic applications. However, realization of facet-specific heterojunction remains challenging; yet it has been rarely studied in electrocatalysis. In this work, we first report the enhanced electrocatalytic performance of monolith Au/Si (111) heterojunction on Si micron-scale pyramids, prepared by alkaline Si-wafer etching with surface decoration of isolated gold nanoparticles (5–15 nm). The Au/Si (111) heterojunction exhibits the facet-dependent electrochemical activities superior to Au/Si (100). Varied Si etching levels enable the mixed exposure of Si (111) and Si (100); and the results further support the facet-dependent electrochemical enhancement. By excluding the effects of surface areas and defects, studies on the role of Si (111) reveal that the Au/Si (111) interface is very essential in improving the sensitivity and the detection limit at the heterojunction. This means that usage of well-controlled facets instead of merely facilitating electron transport can be considered in heterojunction electrocatalyst design. The H2O2 sensing performance of Au/Si (111) is synergistically enhanced achieving 194 times greater sensitivity than the Au/Si (100) with a wide linear range from 0.01 to 55.55 mM, high sensitivity (171 μA mM−1 cm−2), and low detection limit of 1.24 μM.