Sustainable energy can be achieved by electrochemically splitting water to give hydrogen and oxygen. Afterwards, hydrogen and oxygen recombine, in a separate reaction, to generate energy, producing water in the process. Thus, sustainable and efficient energy generation is obtained via chemical bonds. The limiting half reaction for water splitting is the oxygen evolution reaction (OER). Currently, the best catalysts for OER contain rare metals such as, IrO₂ and RuO₂, therefore, not suitable for mass production. Researches have shown that perovskite structures exhibit high catalytic activity for OER as they can possess rich combinations of transition metals in their structure, which have different oxidation states and coordination environments, resulting in tunable OER behaviors. The perovskite substitution space is quite large leading to an efficient way to discover new catalysts, therefore, combinatorial material synthesis and screening is used for high-throughput experimentation. It has a high potential to accelerate the discovery of functional materials by creating large material composition libraries.

In this work, a sustainable abundant catalyst for OER reaction is investigated and characterized through combinatorial methods. By using the combinatorial method we are able to study the effects each element has on OER electrocatalytic activity with varying concentration in the perovskite structure. Here, a 3D nano-structured La_xCa_1-xFe_yNi­_1-yO_z was fabricated by e-beam with compositional gradient of La, Ca, Fe, and Ni, which are non-rare elements. The fabrication process was done by the graded deposition of the above materials using glancing angle e-beam onto a single substrate and then annealing at 680°C. As a control experiment, LaNiO₃ and LaFeO₃ perovskites were obtained using the same fabrication method. The compositional gradient was formed by distorting the e-beam during a co-deposition, while simultaneously, nano-structures were formed by the glancing angle deposition (GLAD) technique, increasing the surface area. The chemical analysis of the compositional gradient was done by point-by-point energy-dispersive X-ray spectroscopy (EDS) on the combinatorial sample and the perovskite crystal structures were confirmed using X-ray diffraction (XRD). Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were used to measure the electrocatalytic activity. In conclusion, the nano-perovskite OER electrocatalysts, fabricated using combinatorial methods, can be used in potential sustainable systems. The combinatorial fabrication using the GLAD technique is a highly promising method to synthesize multi-elemental complex perovskites and to accelerate functional material discoveries.