Silicon Nanowires as Photoelectrodes for Carbon Dioxide Fixation

Abstract

Licht an: Beim Bestrahlen übertragen Si‐Nanodrähte vom p‐Typ photogenerierte Elektronen auf aromatische Ketone, wodurch reaktive Radikale entstehen, die mit CO2 zu α‐Hydroxysäuren reagieren (siehe Schema). Das Reaktionsschema mit einer Ausbeute und Selektivität bis 98 % ähnelt stark dem der natürlichen Photosynthese. Zu den auf diesem Weg erhaltenen Produkten gehören wichtige Vorstufen für nichtsteroidale Entzündungshemmer wie Ibuprofen und Naproxen.

Silicon Nanowires Show Improved Performance as Photocathode for Catalyzed Carbon Dioxide Photofixation

“…To the best of our knowledge, our report is the first to systematically compare photoelectrodes of SiNWs and planar Si in a synthetically useful system. A consistent trend, albeit in a much less pronounced magnitude, was observed in our proof‐of‐concept demonstration of the benzophonene system 8. Previous considerations13, 19, 20 about the trade‐off between photovoltage reduction caused by surface states and better charge collection by the NW morphology are generally valid.…”

“…6 Relatively underwhelming attention is paid to issues related to low product specificities when CO 2 is reduced. Inspired by the detailed mechanisms of the dark reactions in the Calvin cycle,7 we recently reported a strategy to combat this problem 8. Briefly, the key was to avoid direct reduction of CO 2 , which is prone to produce carbon atoms of varying oxidation states.…”

Solar Hydrogen Generation by Silicon Nanowires Modified with Platinum Nanoparticle Catalysts by Atomic Layer Deposition

“…For a semiconductor‐based PEC system, the current reaches saturation because of a limitation of the ionic diffusion in the electrolyte, or because of electronic limitation in the semiconductor, or both. Previous research by us and others have shown that SiNWs can deliver photocurrent densities >30 mA cm −2 , when effective redox species are present 11. 12, 21, 22 The same holds true for planar Si and SiNWs without catalyst at low applied bias (Figure S4).…”

Visible-light photoredox-catalyzed umpolung carboxylation of carbonyl compounds with CO2

“…Compared to cyanide and carbon monoxide, CO 2 represents a better choice as a C1 source in carboxylation due to its abundance, nontoxicity, and recyclability 31 – 39 . Although significant progress has been achieved in recent decades to generate α-hydroxycarboxylic acids with CO 2 18 – 20 , 40 – 43 , most of these methods suffer from the utilization of stoichiometric amounts of metal reductants, low functional group tolerance, limited substrate scope, and/or competitive side reactions, especially the pinacol coupling and reduction, thus hampering industrial application. Therefore, a general and practical method is desirable.…”