In the context of aluminum and hydrogen fuel cells, why is using aluminum unsuitable?

Using aluminum in hydrogen fuel cells is unsuitable primarily because it forms an oxide layer. This oxide layer, known as aluminum oxide, is incredibly stable and acts as a protective barrier that prevents further oxidation of the aluminum metal. In the context of a fuel cell, where various chemical reactions are necessary for generating electrical energy, the presence of this oxide layer would significantly hinder the reaction processes. Essentially, it prevents the aluminum from participating effectively as a fuel, thereby reducing the efficiency of the fuel cell.

In electrochemical applications, the electrochemical activity of the reactants is vital for efficient energy production. The oxide layer can passivate the aluminum, inhibiting its ability to react with other species within the fuel cell system. This characteristic becomes particularly problematic in scenarios where continuous and effective reaction surfaces are required.

Considering the other options, while aluminum does react with hydroxide ions in some contexts, this reaction is not the fundamental reason for its unsuitability in fuel cells. Although aluminum does have a relatively low melting point, this property alone does not critically impair its performance as a fuel. Lastly, while producing excessive heat can be a concern in certain reactions, it is not the primary issue associated with aluminum’s use in hydrogen fuel cells. The formation of the oxide layer remains