The formic acid oxidation reaction has been studied in concentrated perchloric acid solutions (up to 9.14 M (60%)) on the Pt (111) surface to explore the relationships between interfacial properties and kinetics. It is found that, as the concentration of perchloric acid in the supporting electrolyte increases, the current markedly decreases, making it possible to detect adsorbed formate on the surface by voltammetric methods. With the aid of DFT calculations, it is shown that the diminution in current is the result of two opposing factors: the reduction in the concentration of free formate in solution and electrode charge effects which encourage the adsorption of formate in a particular configuration. Additionally, the electrochemical behavior under highly acidic conditions suggests the formation of clathrate structures and emphasizes the relevance of the water structure effect in electrode adsorption processes.