Natural dye sensitizer in photoelectrochemical shows a great potential in improving the efficiency of metal oxide semiconductor especially Titanium dioxide (TiO 2 ) due to its prominent in absorbing visible light and also low cost. In this work, the effect of using pitaya peel as natural dye sensitizes to TiO 2 has been studied through characterizations analysis and PEC test. The bare TiO 2 thin films were fabricated on Fluorine-doped tin oxide (FTO) glass substrate by doctor blade method meanwhile dyesensitized TiO 2 thin films prepared by immersion of TiO 2 in the dye extracts. The fabricated thin films were characterized with Scanning Electron Microscopy (SEM), X-ray difractometer (XRD), UV-Vis spectrophotometer and photoelectrochemical analysis. The surface of TiO 2 was porous and uniform meanwhile dye particles could not been observed due to very small size. The energy band gap of dye-sensitized TiO 2 from the UV-Vis spectrum is 2.1 eV which is smaller than bare TiO 2 (3.7 eV). Meanwhile, photoactivities of dye-sensitized TiO 2 has the highest compared to bare TiO 2 photoelectrodes which is 127µA/cm 2 in 6.25% v/v of pitaya dye in the electrolyte.Keywords: titanium dioxide, dye-sensitizers, betalains, photoelectrochemical cell, water splitting Abstrak Pemeka-pewarna semulajadi di dalam fotoelektromia (PEC) menunjukkan potensi yang bagus untuk meningkatkan keupayaan semikonduktor logam oksida terutamanya titanium dioksida (TiO 2 ) disebabkan kemampuannya untum menyerap cahaya nampak dan kos yang rendah. Di dalam penyelidikan ini, kesan menggunakan kulit buah naga sebagai pemeka-pewarna semulajadi terhadap TiO 2 telah dikaji melalui pencirian dan analisis fotoelektrokimia. Filem nipis TiO 2 asli telah dihasilkan melalui kaedah Doctor blade di atas kepingan kaca bersalut FTO (Stanum oksida terdop fluorin) manakala filem nipis TiO 2 dengan pewarnapemeka telah dihasilkan dengan merendam TiO 2 ke dalam larutan ekstrak pewarna. Filem nipis yang telah terbentuk telah melalui beberapa analisis pencirian iaitu, Mikroskopi Elektron Imbasan (SEM), Difraktometer Pembelauan Sinar-X (XRD), Spektrofotometer Ultralembayung dan Cahaya Nampak (UV-Vis) dan juga ujian fotoelektrokimia. Permukaan TiO 2 adalah berliang dan seragam manakala zarah pewarna tidak dapat dilihat disebabkan saiznya yang terlalu kecil. Jurang tenaga filem nipis TiO 2 dengan pewarna-pemeka adalah lebih rendah iaitu 2.1 eV jika dibandingkan dengan TiO 2 asli (3.7 eV). Manakala, fotoaktiviti bagi fotoelektrod TiO 2 dengan pewarna-pemeka adalah lebih tinggi daripada TiO 2 asli dengan 127µA/cm 2 di dalam kepekatan 6.25% v/v pewarna di dalam elektrolit. ISSN -2506 Siti Nur Hidayah et al: EFFECT OF USING PITAYA PEEL AS DYE-SENSITIZER AND DYE MOLECULES IN ELECTROLYTE FOR PHOTOELECTROCHEMICAL REACTION 652Kata kunci: titanium dioksida, pemeka-pewarna, betalain, sel fotoelektrokimia, pembelahan air Introduction The hydrogen gas production by using solar energy is deliberated as one of the most significant sustainable and clean energy technologies [1]. Photo...
The clean and recyclable production of hydrogen gas by water splitting over a semiconductor photocatalyts using solar energy is a promising process. Photoelectrochemical (PEC) water splitting is one of most favourable hydrogen production technologies. The development of TiO 2 semiconductor has been widely studied for its efficiency reasons. However, the large band gap of TiO 2 can only absorb UV light thus reducing its performance in PEC. Besides, recombination of electron-hole pairs also influenced efficiency of photoelectrochemical reaction. Thus, a lot of efforts have been made to increase the performance of PEC and considerably attention is given to dye sensitizers especially natural dye due to their environmental friendliness and low cost. Hence, this research studied the natural dye of pitaya peel which contains betalains due to its availability in local area and low in conservation cost. Thus, the physical and chemical characterization of TiO 2 thin film with dye has been investigated through SEM, XRD and UV-Vis analysis. The optical absorption for the dye is 546 nm show good absorption in visible light with band gap 2.3eV. For photoelectrochemical properties, photoelectrode TiO 2 /dye/PEDOT:PSS has the highest photocurrent which are 0.62 μAcmand increased further to 1.4 μAcm -2 with the addition of pitaya dye in aqueous electrolyte.
Photoelectrochemical (PEC) water splitting is a very promising green method to produce solar fuel. Titanium dioxide (TiO2) has been widely used as photocatalyst for this type of reaction. Improving the performance of TiO2 for PEC water splitting has been ongoing and addition of sacrificial donor especially from waste is an attractive option to achieve this. Oxalic acid is one component in organic waste stream that can be used as sacrificial donor. The TiO2 thin films has been fabricated by coating TiO2 paste on Fluorine Tin oxide (FTO) glass surface. The morphology of the TiO2 thin films were porous and rough with uniform particles size with crystallite size of about 20 nm and dominant anatase peak. The TiO2 photoelectrode undergo PEC testing to measure its photolectroactivity by using oxalic acid as a sacrificial donor in two different type of electrolytes which are distilled water and sodium sulfate (NA2SO4) aqueous solution. The photocurrent produced without addition of oxalic acid is much lower than with the acid. The saturation photocurrent for aqueous NA2SO4 solution and water electrolyte is 0.1 mA/cm2 and negligible respectively. While the photocurrent for addition of oxalic acid in NA2SO4 aqueous solution is 0.5 mA/cm2 and the photocurrent for oxalic acid in water only is 0.9 mA/cm2, which is almost double compared to in NA2SO4 and tenfold in water only. The highest photocurrent produced by TiO2 photoelectrode is by addition of oxalic acid in aqueous (H2O) electrolyte.
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