This thesis project aims at tuning the metallic and superconducting phases in four transition metal dichalcogenides (TMDs) by means of ionic-gate-induced protonation under optimised gating conditions. The ionic-gating technique induces an intense electric field at the interface between an electrolyte and the surface of the material under investigation. The ionic-gate-induced protonation entails the hydrolysis (electrolysis) of the remaining water present in the solution in order to implant H+ ions into the system by exploiting the ultra-high interface electric field. In this thesis work we will focus on a four selected materials, namely TaS2, VSe2,N iTe2 and WSe2 where we use the intercalation of hydrogen and hydrogen-rich ions to induce electron doping and possible structural modifications.