After the PhD and postdocs at the Swiss Federal Institute for Environmental Science and Technology (EAWAG) and at Lawrence Livermore National Lab, Eggleston became an assistant professor at the University of Wyoming in 1995. He had an NSF CAREER award 1998-2003, and spent a sabbatical leave working at EPFL in Lausanne and LCPME in Nancy, France. He was a Fulbright Scholar in south India 2012-2013, and part of an Interdisciplinary Fellowship team at the Rachel Carson Center for Environment and Society in both 2016 and 2017. He was head of the Department of Geology and Geophysics in Wyoming for three years before coming to WPI in 2019. Eggleston has research interests in photoelectrochemistry, semiconducting oxides, scanning probe microscopy applied to crystal growth and interfacial electron transfer, and also in climate change, energy transition, and global energy/environmental trajectory in the Earth System.