One of the ubiquitous properties of life on Earth, and perhaps of any life elsewhere, is that it utilizes geochemical and electrochemical disequilibria and converts free energy. Planets with a water-rock interface generate disequilibria through serpentinization reactions in the form of redox, pH, and thermal gradients at hydrothermal vents. Warm, alkaline serpentinite-hosted vents continually produce fuels which can be utilized as a source of electrons for redox metabolism, and in prebiotic systems, could have formed hydrothermal precipitates (e.g., metal sulfides or oxyhydroxides) capable of catalyzing proto-metabolic reactions and concentrating biologically significant materials. Mineral precipitation chimneys associated with vents can function as chemical flow-through reactors and geochemical fuel cells, driving reactions of carbon / nitrogen / phosphorus compounds and facilitating electron transfer to/from minerals. Some key questions for astrobiology center on understanding the geochemical energy gradients produced on wet rocky planets, including icy worlds such as Europa or Enceladus, and how these abiotic redox and pH gradients may have participated in prebiotic chemistry and the emergence of bioenergetics.