Hydrogen produces a fairly clean fuel with water being its only emission. However hydrogen production is not always environmentally friendly. Conventional methods require natural gas or electrical power which produce waste. The method advanced by direct solar water splitting, only uses water and light from the sun. The new, stable artificial photosynthesis device doubles the efficiency of harnessing sunlight to break apart both fresh and salt water, generating hydrogen that can then be used in fuel cells.
https://www.sciencedaily.com/releases/2018/05/180503142632.htm
This relates to engineering since scientists have applied their knowledge of biological engineering to produce an alternative which is more efficient than the current method being used.
