Can the Interfacial Solar Vapor Generation Performance Be Really “Beyond” Theoretical Limit?

The interfacial solar vapor generation (ISVG) process is an environmentally friendly approach that utilizes solar to produce steam, which can solve the water shortage. Despite many previous research studies, claims beyond the theoretical limit have risen due to limitations in the efficiency of converting solar to vapor and the rate of solar evaporation, which are still being debated. Energy losses remain even under ideal conditions, which means that the efficiency of the system will never be ≥100%. This review primarily analyzes the theoretical values of evaporation rate and energy efficiency in the ISVG process. Utilizing a theoretical formula for energy distribution, the factors contributing to the current exceedance of conversion efficiency and evaporation rate are scrutinized. By examining various strategies, such as the reduction of vaporization enthalpy for photothermal materials and the utilization of environmental energy for evaporation, these studies seek to enhance evaporation efficiencies, but they ignore the problem of the theoretical limit of evaporation. Therefore, this review emphasizes misconceptions about efficiencies beyond theoretical limits and aims to guide researchers to provide plausible explanations for such breakthroughs under specific conditions, alongside established reference conditions. Ultimately, this study lays a solid theoretical foundation for practical solar water purification.