This paper proposes volume of fluid (VOF) model to investigate the potential of Al2O3-water nanofluid to improve the productivity of a single slope solar still. Accordingly, VOF model is utilized to simulate the evaporation and condensation phenomena in the solar still. An entropy generation analysis is used to evaluate the system from the second law of thermodynamics viewpoint. The effects of solid volume fraction of nanofluid on the productivity and entropy generation in the solar still have been examined. The numerical results are compared with the experimental data available in the literature to benchmark the accuracy of VOF model. The numerical results showed that the productivity of solar still increases with an increase in the solid volume fraction of nanoparticles. The productivity increases about 25% as the solid volume fraction increases in the range of 0%–5%. There is about 18% enhancement in the average Nusselt number as the solid volume fraction increases in the range of 0%–5%. Moreover, the maximum values of viscous and thermal entropy generations are happened at the regions around the bottom and top surfaces of the solar still. Both types of entropy generation increase by increasing the solid volume fraction of nanoparticles. The viscous and thermal entropy generations increase about 95% and 25%, respectively as the solid volume fraction increases in the range of 0%–5%. •Potential of nanofluid for improving the productivity of a solar still is studied.•VOF model is used to simulate the evaporation-condensation phenomena.•Productivity of still increases 25% by using nanofluid with volume fraction of 5%.•Maximum entropy generation is occurred near bottom and top surfaces of the still.•Thermal entropy generation is dominant for all considered cases in this research.