The transition from traditional fossil fuels to renewable energy sources requires the development of sustainable energy conversion/storage systems. Highly efficient electrocatalysts play a crucial role in advancing these systems. This dissertation explores the application of metal-organic framework (MOF)-derived electrocatalysts in energy conversion/storage systems, specifically, in anion exchange membrane fuel cells (AEMFCs) and lithium-sulfur (Li-S) batteries. Operando methods have been employed to unveil the fundamental catalytic mechanisms of these MOF-derived electrocatalysts under real-time conditions. In an effort to enhance the sluggish oxygen reduction reaction (ORR) in alkaline media, a group of MOF-derived Pd-Co bimetallic nanoparticle catalysts was designed and optimized. The optimized Pd3Co electrocatalyst exhibited exceptional ORR performance, attributed to the small particle size and uniform elemental distribution throughout the MOF-derived carbon support. In addition, a MOF-derived Zn/Co-N-C ORR catalyst, with atomically dispersed Zn and Co atoms on nitrogen-doped carbon, exhibited outstanding ORR performance as a non-precious-metal catalyst with an ultra-low metal loading. Operando X-ray absorption spectroscopy (XAS) provided insights into the nature of catalytic sites and their dynamic electronic and structural changes during operating conditions. Moving to lithium-sulfur (Li-S) batteries, MOF-derived materials, such as a Co nanoparticle material (Co-NPs/NC), a Co single-atom material (Co-SAs/NC) and a pure MOF-derived nitrogen-doped carbon (NC) were investigated for accelerating Li-S redox reactions. Co-SAs/NC exhibited superior catalytic activity towards the Li-S redox reactions and its electrocatalytic mechanisms were systematically investigated via operando techniques. Real-time observations, through operando confocal Raman microscopy and operando XAS of S K-edge, revealed the zero-order kinetics and the concurrent mechanism of polysulfide conversions under the catalytic effect of Co-SAs/NC. Furthermore, the formation of Co-S coordination bonds during the electrocatalytic process was validated via operando XAS of Co K-edge, shedding light on the role of catalytic sites (Co single atoms). The systematic investigation strategy and operando methods presented in this work offer a deeper understanding of electrocatalysis in fuel cells and Li-S batteries. This knowledge contributes to the advancement of sustainable electrical energy conversion/storage technologies and provides impetus for deciphering complex pathways in other catalytic systems.