The development of fuel cells is indispensable to enable the hydrogen society. Anion exchange membrane fuel cells (AEMFCs) have triggered great interest over the past few years. In this dissertation, electrocatalysis in alkaline media and polymer electrolytes for AEMFCs have been explored from fundamental aspects to practical applications. For the oxygen reduction reaction (ORR) in alkaline media, electrochemically dealloyed Pd-M (M = Ni, Mn) nanoparticle catalysts were developed to enhance electrocatalytic activity. The electrochemical dealloying process was demonstrated to be effective in selectively leaching out the less noble metal and metal oxides on the surface. The higher atomic concentration of electrochemically active Pd exposed on the surface of the nanoparticles was found to be the reason for the enhanced ORR activity in alkaline media. These findings provide insights for the rational design of the composition and structure of electrocatalysts with enhanced electrocatalytic activity, based on post-synthesis modification methods. From a fundamental perspective, to explain and predict the electrocatalytic activity of heterogenous reactions, the energy of intermediates is usually used as an activity descriptor. However, this was recently called into questions. We developed a novel method, based on fast scan rate cyclic voltammetry, to directly measure the kinetics of the electro-adsorption processes. The Had adsorption reaction, the elementary step of the hydrogen evolution reaction (HER), on Pt(111) in acid was found to be >100x faster than in alkaline media, although the Had binding energy was the same. Together, with cation effects and isotope effects found in alkaline media, we demonstrated that the slow kinetics of the HER at high pH are not due to an unfavorable Had binding energy but to the high barrier of interfacial water reorganization. Polymer electrolytes in AEMFCs, namely anion exchange membranes and ionomers, play important roles in the transport of anions and water molecules. In situ characterization of these materials in their electrochemical environment is critical for understanding the anion transport mechanism and improving the design of them. The anion exchange and water dynamics in a perspective phosphonium-based AEM during the methanol oxidation process were studied with the electrochemical quartz crystal microbalance (EQCM). The results provide insights of the anion exchange process in the membranes during the reaction and emphasize the importance of characterizing the membranes in a hydrated electrochemical environment. The influence of ion exchange capacity (IEC) on the solubility, the ionomer viscoelasticity in water and the transport of charged and uncharged species, of a promising polyethylene piperidinium methyl (PEPM) ionomer were also investigated. The design of ionomers and membranes, with suitable IEC for their different functions in AEMFCs from the aspect of solubility, mechanical properties and mass transport, can be guided via this work.