“…To the best of our knowledge, there are few literatures to study the modification of Pd surfaces with acids, although many methods have been developed to control the crystal phase, crystallinity, particle size, shape and composition of Pd surface. [20][21][22][23][24][25][26][27][28][29][30][31] Originally, acetic acid was mostly used to react with palladium and HNO 3 to form palladium acetate, which is a widely used catalyst or precursor in metal-catalyzed organic synthesis. [32][33][34][35][36][37] However, in this work, it is found that acetic acid would only change the morphology of the palladium surface instead of transforming palladium into palladium acetate when HNO 3 is not added into the reaction, which makes it to become a potential method to modify the surface of Pd.…”