on Au-coated (150 nm) fluorine doped tin oxide (FTO) substrates, followed by annealing in sulfur atmosphere. The experimental procedure for electrodeposition of Sb metal has been previously reported. Briefly, Sb metal was electrodeposited on Au-coated FTO substrates in a three-electrode configuration using a solution of potassium antimonyl tartrate (K2(Sb2(C4H2O6)2) and tartaric acid at a pH of 1.3 (adjusted using sulfuric acid) and a potential of -0.3 V vs Ag/AgCl. The Sb metal was then annealed in sulfur atmosphere at different temperatures, ranging from 240 to 300 °C. The sulfurization process was carried out in a 2-zone furnace (Figure ). The tube furnace was evacuated using a vacuum pump and then filled with Ar. This process was repeated 3 times and the sulfurization was carried out under a base pressure of Ar (0.5 bar). A ramping rate of ~ 12°C/min was used to reach the desired sulfurization temperature. The Sb metal on Au-coated FTO substrates were placed in zone 1 (240-300 °C) and elemental sulfur powder (500 mg) was placed in zone 2 (200 °C). The sulfurization was carried out for 40 minutes followed by cooling naturally to room temperature over 60 minutes.