Catalysts, Nickel Phosphide (Cathodic) and LiCoO₂ (Anodic), for Electrolysis of Water

Choice catalysts are required to lower the activation barriers for both the oxidative and reductive half reactions associated with electrolysis of water. Using models provided by natural systems, such as the Ca-Mn cubane motif in the water oxidizing complex of photosystem II and the Ni-S active site of hydrogenase, we have developed LiMO2 (M = Transition metal) 1 and Ni-P compounds which mimic their chemistry2. Thin films of the oxygen evolving reaction (OER) catalyst, cubic LiMO2 (M = Co), and the hydrogen evolving reaction (HER) catalyst, NixPy, are a potentially cost-effective and electrically efficient catalysts for water splitting. Thin films of both the OER and HER catalysts on a transparent conductive oxide substrate and on a light absorbing substrate [Si (100)] have been produced. We shall report the structural, surface, and atomic characterization of these films via x-ray photoelectron spectroscopy, atomic force microscopy, helium ion microscopy, x-ray diffraction, and Rutherford backscattering. These results aid in explaining the (photo-)electro-catalytic properties observed. The cathode and anode can be combined to create a monolithic device that splits water and is discussed in a complementary talk in section I07 titled: “Efficient Solar Water Splitting via Tunable Photoanode-Photocathode-Catalyst Interface Devices”. References Gardner, G. P.; Go, Y. B.; Robinson, D. M.; Smith, P. F.; Hadermann, J.; Abakumov, A.; Greenblatt, M.; Dismukes, G. C. Angew. Chem. Int. Ed. 2012, 51, 1616. Laursen, A. B.; Patraju, K. R.; Whitaker, M. J.; Retuerto, M.; Sarkar, T.; Yao, N.; Ramanujachary, K. V.; Greenblatt, M.; Dismukes, G. C. Energy Environ. Sci. 2015, 8 (3), 1027. Figure 1