The production of hydrogen using photovoltaic–thermal (PVT) solar collectors with minimal environmental impact is a significant issue that necessitates a methodical approach. The selection of an appropriate nanofluid is essential in a thermal collector to optimize the performance of the photovoltaic–thermal (PVT) system and increase the rate of hydrogen production. This study analyzes several nanofluids in terms of viscosity, thermal conductivity, density, specific heat, pumping power, and fluid cost. This study discovered a nanofluid that may significantly enhance the rate of hydrogen generation. To achieve this objective, the analytical hierarchy process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) methods were used to identify the appropriate choice and assess the hydrogen production rate. The findings indicate that a hybrid nanofluid consisting of a 0.2% volume concentration of Al2O3–CuO in water exhibits the most favourable heat transfer characteristics and is considered the best option for improving heat transfer efficiency and boosting the rate of hydrogen generation.