Biophotoelectrochemistry: An emerging frontier for channeling photoelectric effect into darkness zone of soils and sediments

Solar energy captured by photosynthetic plants in the photic zone is recognized as the main driver for the formation of organic matter utilized by soil communities. However, the contribution of organic transformation to the linkage of solar energy and microbial metabolism of soils is reduced when the vadose zone is saturated. In contrast to the conventional biophotoelectrochemistry via photosynthesis with phytoplankton during the periodic saturation of soils, recent studies suggest that non-phototrophic microorganisms in soils and sediments are able to conduct light-dependent metabolism to sustain their functionality with photosensitizers under illumination. These interactions and processes utilize long-distance electron transfer networks to interconnect diverse electron transfer chains that channel photoexcited electrons into the opaque zone for soil communities. Such an emerging process not only allows for a better understanding of biogeochemical processes such as soil carbon sequestration and mitigation, but also shows great potential for environmental treatment such as the bioremediation of contaminated soils. Therefore, we suggest that biophotoelectrochemistry via photoelectric effect can have significant, heretofore unappreciated, theoretical and practical values.