Abstract
Understanding the fundamental thermodynamic limits of photo-electrochemical (PEC) water splitting is of great scientific and practical importance. In this work, a ‘detailed balance’ type model of solar quantum energy converters and non-linear circuit analysis is used to calculate the thermodynamic limiting efficiency of various configurations of PEC design. This model is released as freely accessible open-source (GNU GPL v3) code written in MATLAB with a graphical user interface (GUI). The capabilities of the model are demonstrated by simulating selected permutations of PEC design and results are validated against previous literature. This tool will enable solar fuel researchers to easily compare experimental results to theoretical limits to assess its realised performance using the GUI. Furthermore, the code itself is intended to be extendable and so can be modified to include non-ideal losses such as the over-potential required or complex optical phenomena.
Highlights
Photosynthesis harnesses the solar resource by converting the energy incident on the earth into a storable fuel which has enabled great change in the history of life
The overall chemical equation for water splitting is found in eq (1), where the Gibbs energy of reaction G°
Under standard conditions can be expressed as a cell potential Ec°ell using the equation ΔG° = −nFEc°ell
Summary
Photosynthesis harnesses the solar resource by converting the energy incident on the earth into a storable fuel which has enabled great change in the history of life. In light of the current social and political pressures to move towards a more immediately sustainable future, there has been much hope in realising an economically feasible ‘artificial photosynthesis’ process capable of meeting the modern energy demand One such photo-synthetic fuel commonly studied is hydrogen produced through photo-electrochemical reduction of water. If heat is supplied reversibly from the ambient surroundings at 298.15 K (isothermal), the minimum electrical energy required will be the Gibbs energy of reaction and the minimum cell potential required will be −1.23 V. This value will be used in this analysis and for convenience the negative sign will be dropped : Erxn = −Ecell = 1.23 V. In a solar driven photo-electrochemical cell, this free energy is generated through the excitation of charge carriers in one or more photo-absorbers by www.nature.com/scientificreports/
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