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The antimony selenide semiconductor films (Sb₂Se₃) have been reported as a great light-absorbing material for application on solar water splitting, in addition to being economically viable[1,2]. However, this material is very prone to photocorrosion and high rates of charge recombination, which implies low stability and photocurrent values[3]. In order to circumvent these disadvantages, in the present work we sought to modify the substrate with Pt nanoparticles and to compare the influence of the photoelectrochemical (FED) and electrochemical (ED) deposition methods on the photocatalytic activity of the material. The Sb₂Se₃ electrodes were prepared through potentiostatic co-electrodeposition by applying ‑0.6 V, from a bath composed of SeO 2.0 mmol L^-1 and K(SbO)C₄H₄O₆ 2.5 mmol L^-1 in a supporting electrolyte of 0.5 mol L^-1 Na₂SO₄/H₂SO₄ at pH 2, subsequently the films were submitted to a thermal treatment (300ºC for 1h with Se atmosphere)[4]. For these experiments were used a three electrodes cell with a Pt foil as a counter electrode, Ag/AgCl (KCl sat) as reference electrode, and a substrate of fluorine doped tin oxide glass (FTO) as working electrode. The Pt depositions were performed under lighting (100 mW cm^-2) and controlled potential (-0.1 V) for FED, and only under controlled potential (‑0.1 V) for ED in a photoelectrochemical cell (50 mL) equipped with a quartz window[5]. The Sb₂Se₃ films were used as the working electrode and the same reference and counter electrodes, the Pt precursor solution was composed of 1.0 mmol L^-1 de H₂PtCl₆ in a supporting electrolyte of phosphate buffer 0.1 mol L^-1/Na₂SO₄ 0.5 mol L^‑1 at pH 6.5. The photoelectrodes were characterized by Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Diffuse Reflectance. With this study was verified a typical morphology reported in the literature[1,3], a suitable bandgap of 1.20 eV[2,6], and that both methods of deposition of Pt nanoparticles were effective, but with a greater dispersion of particles by FED. The photoactivity of the Sb₂Se₃ films with Pt deposited (Sb₂Se₃/Pt) were evaluated along the potential applied in the cathodic region by linear sweep photovoltammogram with light pulses of 3 s, in the same photoelectrochemical cell, using a phosphate buffer 0.1 mol L^-1/Na₂SO₄ 0.5 mol L^-1 at pH 6.5 as supporting electrolyte. In order to evaluate the stability of Sb₂Se₃/Pt, a chronoamperometry under transient light was performed at -0.58 V for 660 s, alternating with pulses of 60 s in the light and dark. The photoelectrochemical characterization showed that the insertion of Pt nanoparticles under lighting, led the material to present a photocurrent 3.5 times greater compared to this insertion in the absence of light and 14 times greater compared to the bare semiconductor. This indicates that deposition, besides to occurring in more sites of the substrate, occurs in more photoactive sites, when subjected to FED, allowing more electrons to be available for the reduction of protons during solar water splitting.

Semiconductors, Water splitting, Noble metals deposition, Solar energy materials, Photocatalyst activity