Using Surface Amide Couplings to Assemble Photocathodes for Solar Fuel Production Applications

Abstract

A facile surface-amide coupling method was examined to attach dye and catalyst molecules to silatrane-decorated NiO electrodes. Using this method, electrodes with a push-pull dye were assembled, and characterized by photoelectrochemistry and transient absorption spectroscopy. The dye-sensitized electrodes exhibited hole injection into NiO and good photoelectrochemical stability in water, highlighting the stability of the silatrane anchoring group and the amide linkage. The amide coupling protocol was further applied to electrodes that contain additional proton reduction nickel catalysts for use in photocathode architectures. Evidence for catalyst reduction was observed during photoelectrochemical measurements and via fs-transient absorption spectroscopy demonstrating the possibility for application in photocathodes.

Understanding the Performance of NiO Photocathodes with Alkyl-Derivatized Cobalt Catalysts and a Push–Pull Dye

“… 35 Co is then attached to the linkers via a surface amide coupling procedure we recently developed via coupling of the carboxylic acids of Co with the amine of the linkers to create a surface amide bond. 14 The linkers and Al 2 O 3 layer help separate Co further from the NiO surface (which could help slow Co –NiO and Co–PB6 charge recombination). The different linkers also place Co at varying distances from PB6 .…”

“…Finally, a surface amide coupling procedure was performed to attach Co to the electrodes by soaking the linker-functionalized electrodes overnight in 0.1 mM Co methanol solution containing 1 mM 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) as an amide coupling agent ( Scheme 1 , step 4). 14 Post sensitization, electrodes were rinsed and air-dried affording NiO- PB6 -Al 2 O 3 - L4 - Co , NiO- PB6 -Al 2 O 3 - L8 - Co , or NiO- PB6 -Al 2 O 3 - L11 - Co electrodes. A control sample without linker was also prepared by soaking NiO- PB6 -Al 2 O 3 in a 0.1 mM methanol Co solution overnight, affording NiO- PB6 -Al 2 O 3 - Co electrodes.…”

“…We have also studied the photoelectrochemical performance of NiO- PB6 photocathodes, which show excellent long-term photoelectrochemical stability in aqueous conditions. 14 In separate studies, we found that PB6 is stable under ALD preparation conditions and demonstrated that using ALD of Al 2 O 3 and/or TiO 2 can slow charge recombination on NiO- PB6 electrodes in a variety of assemblies. 41 − 43 Furthermore, ALD is a useful technique as it can be used to build a platform for immobilizing a catalyst further from the metal oxide surface or dye.…”

“… 27 In addition, we have recently developed a surface amide coupling procedure for photocathode assembly where dye or catalyst molecules containing carboxylic acid functional groups can be amide-coupled to amine-derivatized surface-immobilized groups to easily tune and screen a variety of photocathode architectures. 14 …”

Durable photoelectrochemical CO2 reduction with water oxidation using a visible-light driven molecular photocathode

“…To solve this problem, several methods such as stabilization by polymerization of a metal complex, 1,7,[14][15][16][17][18][19][20] formation of an overlayer by atomic layer deposition, [21][22][23] and amide coupling using surface-decorated silatrane anchoring groups 24 are proposed. For example, molecular photocathodes prepared through adsorption of Ru(II) PS and Re(I) CAT units by electropolymerization have been reported by our and Meyer's groups.…”