Over the past few years, the global energy demand has increased significantly. Fossil fuels are the major source of this energy. However, they have been increasing the number of pollutants in the atmosphere and thus intensifying the greenhouse effect. In this scenario, it is necessary to replace this matrix with technologies that are sustainable. The use of hydrogen (H₂) has been highlighted on the world stage because it produces clean energy since the only byproduct of its reaction with oxygen is water. Nevertheless, the majority of hydrogen production (95%) still comes from fossil fuels.

One alternative way to produce hydrogen gas is by the water splitting process. However, the water oxidation reaction is the limiting step, once it is kinetically and thermodynamically unfavorable. Thus, the use of catalysts is necessary. Rare metal oxides (RuO₂, IrO₂) are the state of art for this reaction, nonetheless, their main drawbacks are the high cost and low long-term stability. Cobalt Prussian blue analogues (CoPBA), on the other hand, have received great attention because their kinetics are comparable to state of art catalysts and they are very stable in neutral pH, besides they are easily scalable.

In this work, we synthesized a cobalt-Prussian blue catalyst with different morphologies, and we studied its application in the water oxidation reaction. Moreover, we are putting efforts to understand how the morphology affects the catalyst performance. From Scanning Electron Microscopy (SEM), it can be seen different shapes of CoPBA that have been synthesized until now. Electrochemical measurements for water oxidation were also made, as it can be seen in the presentation.