Catalyst Support Interactions of Highly Active Nife-LDH Towards the Implementation in Photoelectrochemical and Sea-Water Based Water Splitting Technologies

Abstract

For the implementation in photoelectrochemical (PEC) and sea-water based water splitting devices it is of utmost importance to find stable substrates that do not degrade under application related potentials and illumination. While PEC devices incorporate an absorber that has to be protected from the harsh conditions in the electrolyte, the prevalence of Cl- ions in sea-water based water splitting devices leads to corrosion of most metallic substrates under application related potentials. Catalyst coated TiO2 substrates are therefore used as protection layers in PEC devices, while titanium porous transport layers show great stability in anionic exchange membrane sea-water splitting devices.In this study we investigated the interaction between state-of-the-art NiFe-LDH as a catalyst for the OER and titanium substrates. It was shown that the activity of NiFe-LDH on bare Ti/TiOx substrates was very poor. Through the incorporation of thin metal interlayers (Au, Ni) an increase in current density by two orders of magnitude could be observed. Through detailed XPS measurements before and after electrochemical activation of the electrodes we were able to show an improved transformation of the as prepared catalyst into the highly active (oxo)hydroxide phase for the gold and nickel sputtered titanium electrodes. An accelerated stress test performed on these electrodes showed a stable behavior for most electrode assemblies, with Nickel interlayers showing great promise for PEC devices. From our experiments we exclude a pure conductivity enhancement as possible explanation, but instead propose an additional change in the local atomic and electronic structure at the metal-support and metal-catalyst interfaces.