Recently, Nishimura et al. have developed a variable method for preparing shape-controlled PtNPs on graphite surface . In the method, a constant current is applied between a graphite cathode and a Pt anode, the latter of which dissolves to form Pt ions which are reduced at the former. The method is cost friendly because it can be performed in acidic solutions without any reducing and stabilizing agents, i.e., in H2SO4 and HNO3solutions, and also because 72 % of dissolved Pt ions are electrodeposited as PtNPs. This simple method can produce not only tetragonal nanoparticles which are enclosed by (111) planes, that is, thermodynamically stable nanoparticles, but also cubic nanoparticles enclosed by (100) planes. Interestingly, the cubic nanoparticles were preferentially obtained by controlling current densities of the cathode and anode.
In this present work, we studied if gold nanoparticles (AuNPs) could be produced by the same simple method except for employing a gold wire as the anode. Figure 1 shows SEM images of graphite cathodes taken after galvanostatic electrolysis in 0.5 M HNO3 solution for 8 hours. The current densities at the graphite cathodes were (a) -10 and (b) -100 mA cm-2. Note that the main products at the cathode and anode were hydrogen and oxygen due to the electrolysis of water. The images clearly show that AuNPs were electrodeposited on the graphite surface and also that the number of AuNPs obtained at -100 mA cm-2 was larger than that obtained at -10 mA cm-2. Furthermore, the number of AuNPs produced in a 0.5 M H2SO4 solution was found to be larger than that produced in the 0.5 M HNO3solution. In the presentation, we will show the dependence of the number on electrolysis conditions.
 T. Nishimura, T. Nakade, T. Morikawa, H. Inoue, Electrochimica Acta129 (2014) 152–159.