Chemistry at the Interface: Polymer-Functionalized GaP Semiconductors for Solar Hydrogen Production

Abstract

New opportunities for organizing and controlling molecular components arise with the use of a stabilizing organic layer composed of grafted polymer chains at a semiconductor surface. We highlight recent advances in our research efforts to use polymer brush coatings containing pendent ligands that direct and assemble molecular catalysts for fuel production to visible-light-absorbing substrates. We illustrate how the polymeric interface can be varied to control the structure and photoelectrochemical response of gallium phosphide (100) electrodes containing surface-immobilized pyridyl or imidazole ligands with attached cobaloximes for hydrogen production. Surface sensitive spectroscopic methods, including X-ray photoelectron spectroscopy, grazing angle total reflectance Fourier transform infrared spectroscopy, and ellipsometry provide structural information regarding the nanoscale molecular connectivity and mesoscale dimensions of the cobaloxime-containing polymer grafts. At the macroscale, three-electrode photoelectrochemical testing of the cobaloxime-modified electrodes under simulated solar lighting conditions in pH neutral aqueous solutions show up to a 3-fold increase of hydrogen production as compared to results obtained using polymer-grafted electrodes without attached cobaloximes tested under nearly identical conditions.

RuII Photosensitizer‐Functionalized Two‐Dimensional MoS2 for Light‐Driven Hydrogen Evolution

“…The 399.8 eV component was assigned to N-atoms that are coordinated to aR u II center;w hile the lower binding energy Nc omponent was assigned to uncoordinated N-atoms, as are present in bpy-MoS 2 . [43] The emergence of the 399.8 eV in the post-complexation product validates our synthetic efforts of constructing the [Ru II (bpy) 3 ] 2 + entity on the ce-1T-MoS 2 surface. [44] The loading of [Ru II (bpy) 3 ] 2 + photosensitizer in [Ru II (bpy) 3 ]-MoS 2 was estimatedt obea pproximately 10 atomic %p er MoS 2 by calculating the ratio of the amount of coordinated N-atoms to Mo-atoms according to the fitted N1s/ Mo 3p spectra (Figure 4, Supporting Information Figure S7).…”

Artificial photosynthesis: opportunities and challenges of molecular catalysts

“…This is a simple but effective method to modify an electrode with a large amount of the molecular catalyst. [542][543][544][545][546] At the same time, the polymer coating can also be a protective layer for the VLA-SC film. The photocurrent density of this series of hybrid photocathodes for hydrogen evolution is around 1-2 mA cm À2 .…”

A Stress‐Free and Textured GaP Template on Silicon for Solar Water Splitting

“…Many recent proposals deal with the use of the GaP semiconductor as a photoelectrode in PEC devices, especially because its bandgap (2.26 eV) is larger than the 1.73 eV photopotential needed for water splitting . Using this idea, demonstrations of GaP‐based PEC devices and descriptions of the physics/chemistry of the standard GaP surface, its interaction with water and hydrogen generation were reported. To enhance conversion efficiency of GaP‐based PEC devices, strategies like surface functionalization, use of plasmon resonant nanostructures, or integration of nanowires were considered.…”

“…Using this idea, demonstrations of GaP‐based PEC devices and descriptions of the physics/chemistry of the standard GaP surface, its interaction with water and hydrogen generation were reported. To enhance conversion efficiency of GaP‐based PEC devices, strategies like surface functionalization, use of plasmon resonant nanostructures, or integration of nanowires were considered. Meanwhile, it was demonstrated recently that the texturation of surfaces at the electrode level greatly enhances the efficiency of BiVO 4 photoanodes in PEC devices .…”