The article discusses a novel concentrated solar energy conversion system proposed for efficient hydrogen and electricity cogeneration. This system utilizes a parabolic trough collector (PTC) that integrates photocatalysis and Rankine cycle processes. The higher-energy photons are used for water splitting to produce hydrogen, while the lower-energy photons are converted into thermal energy to generate electricity. By reutilizing dissipated heat and radiation heat loss, the system achieves conversion efficiencies of 10.34% and 17.85% for hydrogen and electricity, respectively. This innovative approach increases the total exergy efficiency from 23.51% to 28.49%. The research also analyzes the effects of photocatalyst bandgap and temperature on system performance and demonstrates the optimization of exergy efficiency under various direct nominal irradiation conditions. The system maintains an operational temperature of 140°C when the direct nominal irradiation exceeds 240 W·m−2. Overall, this study provides a promising method to enhance the efficiency and flexibility of full-spectrum solar energy utilization.