Effect of Metal Layer Support Structures on the Catalytic Activity of NiFe(oxy)hydroxide (LDH) for the OER in Alkaline Media

Photoelectrochemical (PEC) cells promise to combine the benefits of photovoltaics and electrolysis in one device. They consist of a photoabsorber functionalized with an electrocatalyst to harvest faradaic currents under reduced overpotentials. To protect the absorber from the harsh reaction conditions, a protective buffer layer (e. g. TiO2) is added between absorber and catalyst. In this work, we investigate the influence of the catalyst support systems Ti/TiOx and Ti/TiOx/M (M=Au, Ni, Fe) on the overall activity and stability of nickel and iron mixed layered double hydroxides for the alkaline oxygen evolution reaction (OER). The catalyst performance on the bare Ti/TiOx substrate is very poor, but the incorporation of a metallic interlayer leads to two orders of magnitude higher OER current densities. While a similar effect has been observed for M=gold supported systems, we show that the same effect can be achieved with M=nickel/iron, already contained in the catalyst. This proprietary metal interlayer promises a cheap OER performance increase for PEC cells protected with titania buffer layers. Detailed XPS show an improved transformation of the starting catalyst material into the highly active (oxy)hydroxide phase, when using metallic interlayers. From these experiments a pure conductivity enhancement was excluded as possible explanation, but instead an additional change in the local atomic and electronic structure at the metal-support and metal-catalyst interfaces is proposed.