Medium-independent hydrogen atom binding isotherms of nickel oxide electrodes

Adsorption and transfer of hydrogen atoms at solid/solution inter-faces are fundamental to heterogeneous catalysis for chemical energy transformations and other processes. Reported here are electrochemical and spectroelectrochemical measurements of the thermodynamics of H-atom binding to nickel oxide electrodes, both the average and the distribution of NiO-H bond dissociation free energies (BDFEs). These are perhaps the first measurements of binding isotherms at non-metal electrodes. Remarkably, both the BDFEs and the non-Langmuirian isotherms are the same in water, acetonitrile, and dimethylformamide, and with different buffers and proton activities. Such medium independence of the BDFEs and isotherms has not been previously reported for any bi-nary material. The medium independence supports the common use of computed hydrogen binding energies as intrinsic descriptors of surface reactivity, while the broadened isotherms add a level of complexity to such analyses. This work demonstrates the capability to derive key thermodynamic parameters at chemically reactive solid-liquid interfaces.

Automated summary

This study investigates the thermodynamics of hydrogen atom binding to nickel oxide electrodes by electrochemical and spectroelectrochemical measurements. It reveals that the binding energies and isotherms are independent of solvent and proton activity, which is not previously reported in other materials.