Supplementary Material (ESI) for Chemical Communications

The nickel phosphide thin films were electrochemically deposited on FTO glass (3.1 mm thick, 13 Ω/ , Nippon Sheet Glass) using potentiostatic (PS) and periodic pulse-reverse (PR) techniques at room temperature in a homemade three-electrode cell. FTO, Pt foil, and SCE (saturated calomel electrode) were used as the working, auxiliary, and reference electrodes, respectively. The deposition bath consisted of NiSO4⋅6H2O (80 g L), NiCl2⋅6H2O (30 g L), H3PO3 (25 g L), and H3PO4 (40 g L). The PS deposition was carried out by applying a voltage of -0.8 V vs. SCE for 50 min. The periodic PR deposition was carried out by applying a voltage of -0.8 V vs. SCE for 6 s and a reverse voltage of 0.1 V vs. SCE for 24 s, the periodic voltage was repeated for 500 cycles. After deposition, the film electrodes were rinsed with deionized water followed by heat-treated in nitrogen atmosphere at 500°C for 1 h. For comparison, the Pt/FTO electrode was fabricated by thermal decomposition of hexachloroplatinic acid (5 mM in isopropanol) on FTO glass at 425°C in air for 30 min.