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Chapter 1

The Challenge of Water Splitting in View of Photosynthetic Reality and of Research Trends

When the path of energy is followed from solar light to chemical energy in the form of hydrogen (equivalent) from water splitting, remarkable differences are recognised between the natural photosynthetic system and advanced artificial models. The latter, based on reversible thermodynamics and classical kinetic theory, in principle, work as essential energetic, kinetic and catalytic preconditions are understood, and noble metal based catalysts are applied. But after half a century of research, they still do not promise an economic fuel technology. Nature, three billion years ago, while utilising abundant and sustainable materials, ventured into a quite differently tailored water splitting strategy and did not correct it later on. No permanent potential gradient is imposed for charge separation, electron transfer is rectified on a molecular level, the overpotential for oxygen evolution is minimised by generating an activation complex as dissipative structure, and a radical formation avoided via coordinated multi-electron exchange. Such phenomena are only accessible within the framework of irreversible thermodynamics and require, for implementation, a change of paradigm towards a fundamental time arrow. If performed, our present understanding of photoelectrochemistry, based on time invertible laws and quantities of state, still remains valid, but as a limiting case, where self-organised mechanisms are not to be expected.

Publication details

Print publication date
12 Apr 2018
Copyright year
Print ISBN
ePub eISBN
From the book series:
Energy and Environment Series