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

Abstract

International audienceThe electrocatalytic redn. of CO2 to CO in hydroorg. medium has been investigated at illuminated (λ \textgreater 600 nm; 20 mW cm-2) hydrogen-terminated silicon nanowires (SiNWs-H) photocathodes using three Mn-based carbonyl bipyridyl complexes as homogeneous mol. catalysts ([Mn(L) (CO)3(CH3CN)](PF6) and [Mn(bpy) (CO)3Br] with L = bpy = 2,2'-bipyridine and dmbpy = 4,4'-dimethyl-2,2'-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-H in terms of cathodic photocurrent densities and overpotentials. For example, the photocurrent densities measured at -1.0 V vs SCE for [Mn(bpy) (CO)3(CH3CN)](PF6) at SiNWs-H exceeded 1.0 mA cm-2 in CO2-satd. CH3CN + 5% vol./vol. H2O, 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\textbarMn-based catalyst interfaces. The fill factor FF and energy conversion efficiency η calcd. under catalytic conditions were higher for [Mn(bpy or dmbpy) (CO)3(CH3CN)](PF6) (FF = 0.35 and 0.34; η = 3.0 and 2.0%, resp.). Further preparative-scale electrolysis at SiNWs-H photocathode with Mn-based complex catalysts in electrolytic soln. evidenced the quant. conversion of CO2 to CO with a higher stability of the [Mn(dmbpy) (CO)3(CH3CN)](PF6) complex. Finally, in order to develop technol. viable electrocatalytic devices, the elaboration of SiNWs-H 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

Boron-doped diamond semiconductor electrodes: Efficient photoelectrochemical CO2 reduction through surface modification

“…first reported photoelectrochemical CO 2 reduction to produce formic acid, methanol and formaldehyde using a p-type GaP semiconductor in 1978. Since then, many semiconductor photocatalysts have been used for CO 2 reduction23242526. Metal nanoparticles deposition on the semiconductors and fabrication of metal-semiconductor junction have successfully studied for improvement of photocatalytic CO 2 reduction activity272829.…”

Semiconductor‐Based Photoelectrochemical Conversion of Carbon Dioxide: Stepping Towards Artificial Photosynthesis

“…Later, through the addition of water and variation in the concentration of [Re(bipy‐ t Bu)(CO) 3 Cl], the heterogeneous cathode was able to generate syngas (H 2 /CO=2:1) with a total FE of (102±5) %; this was the first example of the cogeneration of H 2 and CO in a mixed homo‐/heterogeneous system . Torralba‐Peñalver demonstrated the performance of manganese‐based carbonyl bipyridyl complexes as molecular catalysts ([Mn(L)(CO) 3 (CH 3 CN)](PF 6 ) and [Mn(bpy)(CO) 3 Br] (L=bpy and 4,4‐dimethyl‐2,2′‐bipyridine (dmbpy)) bound to hydrogen‐terminated silicon nanowire (Si NW‐H) photocathodes for CO 2 reduction (Figure b) . [Mn(bpy)(CO) 3 (CH 3 CN)](PF 6 ) coupled to Si NWs‐H manifested a superior catalytic current of more than 1.0 mA cm −2 , as measured at −1.0 V versus SCE, compared with that measured on planar Si−H and glassy carbon electrode, owing to the degree of band bending and depth of the space–charge layer, which was always greater for Si NWs‐H.…”

“…), b) hydrogen‐terminated silicon nanowires (Si NWs‐H) and Mn I ‐based carbonyl bipyridyl molecular catalyst (reproduced with permission from ref. ), c) Cu 2 ZnSnS 4 (CZTS) and InP–metal complex hybrid photocatalyst (reproduced with permission from ref. ), and d) Cu 2 O photocathodes and a Re‐based molecular catalyst (reproduced with permission from ref.…”

Heterogene molekulare Systeme für eine photokatalytische CO2‐Reduktion mit Wasseroxidation

“…[261][262][263][264][265][266][267] Angesichts eines breiten Spektrums an sichtbares Licht absorbierenden Farbstoffen und hoch effizienten Metallkomplexkatalysatoren bieten molekülmodifizierte PEC-Vorrichtungen ein großes Potenzial füre ine leistungsfähige künstliche Photosynthese. [47,54,55,[268][269][270][271][272] Arai et al modifizierten ein p-InP mit einem elektropolymerisierten Ru-Komplex als Photokathode zusammen mit einer Ag/AgCl-Referenzelektrode und einer Glaskohlenstoff-Gegenelektrode. [47,54,55,[268][269][270][271][272] Arai et al modifizierten ein p-InP mit einem elektropolymerisierten Ru-Komplex als Photokathode zusammen mit einer Ag/AgCl-Referenzelektrode und einer Glaskohlenstoff-Gegenelektrode.…”