Towards photoexcited diamond as a source for solvated electrons

Chemically recycling carbon dioxide into fuels via artificial photosynthesis requires an electron source to reduce carbon dioxide. In this talk, we explore how photoexcited diamond has potential to be be used as this electron source. When the surface is treated with hydrogen, diamond has the rare property of posessing a negative electron affinity, meaning that its conduction band minimum lies above the vacuum. Thus, photoexcited diamond freely emits electrons, which can in turn be used for reducing molecules such as carbon dioxide. Such electron emission has been demonstrated previously with above-gap ultraviolet light in water, producing free electrons that can drive high energy chemical reactions. Notably, sub-gap light on n-type nanocrystalline diamond on metal substrates has also been shown as a vacuum electron source, and holds the record for the lowest photo-threshold of any non-cesiated material at 1.5eV. In this work, we show recent results generating solvated electrons with diamond, chemical reactions enabled by these solvated electrons, and discuss the stability of the diamond surface for long-term use.