State-of-the-Art Advances, Development, and Challenges of Metal Oxide Semiconductor Nanomaterials for Photothermal Solar Steam Generation

Solar steam generation has drawn high levels of attention from the research community in recent years due to its wide application and abundantly available energy source-sunlight. To the best of the author's knowledge, a specialized overview of photothermal semiconductor solar steam generation has not been conducted to date. In this review, the recently reported solar evaporators using metal oxide semiconductors as the photoabsorber material are investigated, from the perspective of nanostructure, synthesis method, and installation method. A timeline sequence map is generated with the CiteSpace analysis tool to visualize the trend of metal oxide semiconductors as photoabsorbers. The nanostructure of metal oxide semiconductor is emphasized, due to its significant effect on regulating photothermal efficiency in solar steam generation. In addition, other considerations are suggested to enable a fair evaluation of future synthesized photoabsorbers, including cost, stability, reproducibility, recyclability, and regenerative ability. A brief summary of divergent application of solar steam generation is conducted to show the merits of solar steam generation, as well to provide insights for production of photoabsorbers targeted to varying usage and scenarios. Furthermore, the challenges and opportunities of metal oxide solar steam generation system are elaborated from the viewpoint of the authors, with the aim to provide useful insights for future development of photothermal solar steam generation.