Hydrogen evolution reaction (HER) was studied on carbon paste electrodes modified by series of 1:1 clay minerals (kaolinite and halloysite) supported palladium nanoparticles (PdNPs). To improve the compatibility of PdNPs with clay minerals, these were functionalized by an imidazolium based ionic liquid. Despite the better accessibility of PdNPs loaded on kaolinite external surfaces, halloysite based materials were the most efficient catalysts for HER, plausibly because of the exceptional localisation of PdNPs in the lumen. The capacity of these materials to easily produce hydrogen was used to develop an original method for the electrocatalytic determination of p-nitrophenol (P-NP) in trace levels in aqueous solution. The catalytic mechanism proceeds via the chemical reduction of p-hydroquinoimine (P-QI) into p-aminophenol (P-AP) by hydrogen, followed by the electrochemical oxidation of the later to yield P-QI. The signal obtained was very stable and five times higher than the one obtained from the direct reduction of P-NP frequently used for its determination. At optimal experimental conditions, a detection limit of 22 nM with a relative standard deviation of 2.5% was obtained.