Biotemplated nickel iron oxide electrocatalysts for efficient oxygen evolution reaction

Earth-abundant microalgae have emerged as attractive carbon-based scaffolds for the growth of electrocatalysts. In our previous research work on algal cells Tetraselmis, the cell framework was retained after carbonization treatment. To further investigate whether this approach could be extended to other types of algal cells to preserve the cell framework, in this work, we use algae Nannochloropsis oculata as a biotemplate to synthesize the promising oxygen evolution reaction (OER) nanocatalysts, nanostructural NiFe oxides (NiFeOx). Two approaches have been implemented. The first approach involves directly using algal cells as a biotemplate for growing NiFeOx nanoparticles at different pH levels under mild conditions by hydrothermal reactions. The second approach includes first carbonizing algal cells via thermal annealing, which then serve as scaffolds for NiFeOx growth. The resulting samples were characterized with techniques such as X-ray diffraction and transmission electron microscopy, and their electrocatalytic properties were evaluated using cyclic voltammetry and linear sweep voltammetry. Results show that the best performance for the first approach is at pH 9.0 with significant OER activity, and in the second approach, the pH 8.0 sample demonstrates improved performance compared to benchmark catalysts.