At the ESRF the electrochemical measurements were performed in a cell that allows for operando SXRD measurements, which is similar to the one described in Ref. For this work, we employed a Ag|AgCl|3.5M KCl (eDaq company) RE and a glassy carbon CE. The potential was controlled with a Biologic SP300 potentiostat. All potentials were converted to the RHE scale. A more detailed description of the electrochemical procedure at the ESRF is provided in the Section. S6.