Nano-sized Pd particles are uniformly dispersed on graphene nanosheets (GNSs) using a supercritical-fluid-assisted deposition technique to increase the electrochemical sensing properties. The incorporation of different kinds of ionic liquid (IL) can increase the electrode sensing current toward different analytes. Butylmethylpyrrolidinium–bis(trifluoromethanesulfonyl)imide (BMP–TFSI) IL is beneficial for glucose detection, whereas the electrode with butylmethylpyrrolidinium–dicyanamide (BMP–DCA) IL shows high sensitivity toward ascorbic acid (AA). The selective detection of glucose or AA from their mixture is for the first time demonstrated using a non-enzymatic electrode with the aid of an IL. Angle-resolved X-ray photoelectron spectroscopy analyses indicate that GNSs can create an aligned cation/anion orientation in the adsorbed IL film, with the anions preferentially occupying the topmost surface. As a result, the electrode sensitivity and selectivity are mainly determined by the IL constituent anions.