Photocatalysis for Hydrogen Production: Superiority or Inferiority Compared to Solar Cells, and Common Issues

Photocatalysts and solar cells operate on similar principles and share many development challenges and solutions. Therefore, we shall examine what led to the commercialization of solar cells and discuss its implications for the future of photocatalysts. Indeed, over the past quarter-century, whether intentionally or not, photocatalysts have developed systematically along the established path of solar cells, as evidenced by the development of visible-lightresponse and/or Z-scheme type photocatalysts. In particular, this paper examines electron–hole recombination, reviewing recent attempts to suppress it by increasing purity and introducing an internal electric field, even in photocatalysts. These advancements open new possibilities for achieving high-performance in photocatalysis.