From a theoretical perspective, when we study the electrocatalytic efficiency of a modeled catalyst, we calculate its overpotential. Here the contribution of pH to energy change for each reaction step is given by (pHk_bTln10). Now the question is, we add the value ((pHk_bTln10)) to each reaction step, then the overall free energy change for each reaction step remains the same which means the overpotential will remain the same irrespective of what pH value we are studying.
" the contribution of pH to energy change for each reaction step is given by (pHk_bTln10) " is not correct. The catalytic OER and ORR are multistep processes. Each 1e transfer reaction has its own pH dependence.
Yurii V Geletii thanks for the answer, but yes... it's a multi-step process, my question was how to add the pH effect for each step?
The protonation changes the structure of a catalyst in different oxidation states. You need to calculate the pKas and to determine which species are dominant at each pH. In other words, you need to build a Pourbaix diagram of your catalyst.
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