This study presents a comprehensive 3D and time-dependent simulation of a planar solid oxide fuel cell (SOFC), focusing on the intricate interplay between microstructural characteristics and multiphysics phenomena. The simulation framework integrates detailed microstructural models with advanced multiphysics simulations to capture the coupled effects of electrochemical reactions as well as mass transport and heat transfer within the 3D representative volume elements (RVE) of SOFC porous electrodes generated, and their effective properties are estimated. The energy conversion performances of a SOFC unit are predicted using finite element analysis to solve the governing equations for the coupled phenomena over time. This approach enables us to elucidate the impact of microstructural features such as pore size distribution, tortuosity, and phase connectivity on the overall cell performance. The results demonstrate critical insights into the transient behaviour of the SOFC under various operating conditions, highlighting the importance of microstructural optimisation for enhancing efficiency. This work bridges the gap between microstructural analysis and macroscopic performance prediction, providing valuable guidelines for the design and development of high-performance SOFCs.