Nanostructured Boron Doped Diamond Electrodes with Increased Reactivity for Solar‐Driven CO₂ Reduction in Room Temperature Ionic Liquids

Abstract

Conductive, boron doped diamond (BDD) is an extraordinary material with many applications in electrochemistry due to its wide potential window, outstanding robustness, low capacitance and resistance to fouling. However, in photoelectrochemistry, BDD usually requires UV light for excitation, which impedes e. g., usage in CO2 to fuel reduction. In this work, a heavily boron doped, nanostructured diamond electrode with enhanced light absorption has been developed. It is manufactured from BDD by reactive ion etching and presents a coral‐like structure with pore diameters in the nanometer range, ensuring a huge surface area. The strong light absorbance of this material is clearly visible from its black color. Consequently, the material is called Diamond Black (DB). Electrochemical and X‐ray photoelectron spectroscopy measurements performed at near‐ambient pressure conditions of water vapor demonstrate increased surface reactivity for the hydrogen‐terminated DB compared to oxidized surfaces. Depending on the surface termination, the wettability and hence the electrochemically accessible area can be changed. Photoelectrochemical conversion of CO2 was demonstrated using a Cu2O‐modified electrode in ionic liquids under solar illumination. High formic acid production rates at low catalyst deposition times can be obtained paired with an increased catalyst stability on the DB surface.

LIPSS Applied to Wide Bandgap Semiconductors and Dielectrics: Assessment and Future Perspectives

“…Once the scalability, repeatability and controllability of preparation and processing methods of LIPSS has settled down, the correlation between the specific surface chemistry and topography will be conclusively established in the finished product. These will supply more drawings for applications of WBS and dielectric materials for which surface functionalization is one of the most important features (e.g., catalysts [109], nano and micro-electronics [110], bio-sensing [111], energy conversion [60,112], electrochemical and photoelectrochemical processes [71,113], elementary optical devices such as selective absorbers [80], THz optical components [72,114], etc. ).…”

Early dynamics of the emission of solvated electrons from nanodiamonds in water

“…Visible-light reactivity toward CO2 photoelectrochemical reduction was recently demonstrated on hydrogenated nanostructured diamond surface by some of us. 21 The origin of enhanced reactivity with visible light remains elusive so far. Thus, identifying electron emission processes involved in sub-bandgap (visible) excitation would certainly facilitate the design of more efficient diamond-based electron emitters.…”

Impact of Nitrogen, Boron and Phosphorus Impurities on the Electronic Structure of Diamond Probed by X-ray Spectroscopies

“…However, electron photoemission requires diamond illumination with deep UV light to overcome the diamond band gap and is therefore fairly inefficient with visible light illumination. In order to increase the diamond light absorption, nanostructuring [3,4], combination with dyes absorbing in the visible spectrum [5,6] and incorporation of metal nanoparticles to generate plasmonic effects [7] have been proposed. Incorporation of heteroatoms in the diamond matrix to add new absorption states is another approach that has also been shown to enable visible light absorption [8].…”