Optimal algorithms for energy management and component sizing play essential roles in reducing energy consumption and prolonging fuel cell durability of fuel cell electric vehicles. These two problems are usually coupled together, and it is of great importance to study. In this work, an energy consumption and durability model of a bus with a combined fuel cell, battery, and supercapacitor powertrain are introduced. A two-dimensional (2D) dynamic programing (DP) algorithm was designed to minimize energy consumption and system degradation. A real-time energy management strategy based on a 2D Pontryagin's Minimal Principle (2DPMP) was then proposed. Simulation results indicated that the proposed 2DPMP strategy can approximate the optimal strategy of dynamic programming well and showed a reduction in energy consumption and an increase in durability over other strategies. Component parameters and energy management strategy were simultaneously optimized based on the 2DPMP strategy, thus providing a set of optimal powertrain parameters on a Pareto front. Design rules for energy management strategy and component sizing were concluded from the set of optimal solutions. (C) 2019 Published by Elsevier Ltd.