Selective Catalytic Electroreduction of CO2 at Silicon Nanowires (SiNWs) Photocathodes Using Non-Noble Metal-Based Manganese Carbonyl Bipyridyl Molecular Catalysts in Solution and Grafted o

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• 作者：Encarnaci贸n Torralba-Pe帽alver ; Yun Luo ; Jean-Daniel Compain ; Sylvie Chardon-Noblat ; Bruno Fabre
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：October 2, 2015
• 年：2015
• 卷：5
• 期：10
• 页码：6138-6147
• 全文大小：506K
• ISSN：2155-5435

文摘

The electrocatalytic reduction of COb>2b> to CO in hydroorganic medium has been investigated at illuminated (位 > 600 nm; 20 mW cm^鈥?) hydrogen-terminated silicon nanowires (SiNWs鈥揌) photocathodes using three Mn-based carbonyl bipyridyl complexes as homogeneous molecular catalysts ([Mn(L) (CO)b>3b>(CHb>3b>CN)](PFb>6b>) and [Mn(bpy) (CO)b>3b>Br] with L = bpy = 2,2鈥?bipyridine and dmbpy = 4,4鈥?dimethyl-2,2鈥?bipyridine). Systematic comparison of their cyclic voltammetry characteristics with those obtained at flat hydrogen-terminated silicon and traditional glassy carbon electrodes (GCE) enabled us to demonstrate the superior catalytic efficiency of SiNWs鈥揌 in terms of cathodic photocurrent densities and overpotentials. For example, the photocurrent densities measured at 鈭?.0 V vs SCE for [Mn(bpy) (CO)b>3b>(CHb>3b>CN)](PFb>6b>) at SiNWs鈥揌 exceeded 1.0 mA cm^鈥? in COb>2b>-saturated CHb>3b>CN + 5% v/v Hb>2b>O, whereas almost zero current was measured at this potential at GCE. Such characteristics have been supported by the energetic diagrams built for the different SiNWs|Mn-based catalyst interfaces. The fill factor FF and energy conversion efficiency 畏 calculated under catalytic conditions were higher for [Mn(bpy or dmbpy) (CO)b>3b>(CHb>3b>CN)](PFb>6b>) (FF = 0.35 and 0.34; 畏 = 3.0 and 2.0%, respectively). Further preparative-scale electrolysis at SiNWs鈥揌 photocathode with Mn-based complex catalysts in electrolytic solution evidenced the quantitative conversion of COb>2b> to CO with a higher stability of the [Mn(dmbpy) (CO)b>3b>(CHb>3b>CN)](PFb>6b>) complex. Finally, in order to develop technologically viable electrocatalytic devices, the elaboration of SiNWs鈥揌 photoelectrodes modified with a Mn-based complex has been successfully achieved from an electropolymerizable catalyst, and it was shown that the electrocatalytic activity of the complex was retained after immobilization.