Materials design for iron-based nanomaterials in water treatment and electrochemical energy conversion has largely remained two distinct fields of research and engineering. Yet, the overall goals are the same; materials must be highly active for the target reaction, chemically stable with relevant lifetimes, and tunable for broad applicability and optimization in engineering systems. Further, the detailed characterization performed on catalysts in the electrochemistry arena could benefit efforts to develop catalysts and reactive materials in the water treatment community. Our research focuses on the development of iron-based catalysts and reactive nanomaterials for water contaminant degradation and alkaline electrochemical energy conversion applications, where we synthesize and tune nanoparticle properties, such as phase, composition, and morphology, to target specific reactions. In this talk, I will discuss key examples of how we synthesize our nanomaterials, our work on understanding the roles of nanoparticle structure and composition in reactivity, and opportunities for the synergistic blending of materials design and knowledge of how to design iron-based nanocatalysts for water and energy applications. In particular, an understanding of nanoparticle composition and phase in bimetallic iron-nickel hydroxide nanoparticles for alkaline water electrolysis supports our efforts to design similar catalysts for reductive degradation of the contaminant trichloroethylene, and we are also investigating the role of conductivity in carbon support materials used for water treatment applications. Our work on understanding how nanoparticle synthesis parameters affect nanoparticle performance has led to identification of specific parameters that may be tuned to optimize our catalysts for both arenas, and we have identified specific ligands used during solution-phase synthesis that are important to our catalytic reactions of interest. Overall, there remain many opportunities to draw from experimental progress made in both the water treatment and electrochemistry research communities, and I will touch on several key opportunities that we see in our work.