Water-Splitting Conceptual Approach

The ab initio simulations should be used where they really can make a difference. In this context, it is important to realize that trends and differences are much better described in DFT than absolute numbers. Even semiquantitatively, trends can be obtained. Despite the importance of having an accurate description of the real electrochemical environment for obtaining absolute values, it seems that many trends and relative features can be obtained within a somewhat simpler framework [2], 

In this chapter, the focus will be on trends in electrocatalysis of the water-splitting reaction or the oxygen evolution reaction (OER), which is the reaction at the anode side in an electrolysis cell. Furthermore, simple framework for addressing OER applying DFT simulations will be presented. For further reading, there are two previous book chapters where the approach has been reviewed [3, 4], 

The overall splitting of water into hydrogen and oxygen reads 

This simple reaction is maybe the most studied, and it has been known for a very long time [5], The amount of energy that has to enter in reaction (1) should at least cancel the difference in enthalpy between water and hydrogen and oxygen, which is 5.92 eV at standard conditions. As there are three diatomic molecules on the product side and only two liquid water molecules on the initial side, the entropy 

In the electrochemical cell, the redox reaction is separated into two half-cell reactions - namely, the reduction at the cathode and oxidation at the anode. The sum of 

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