Nanostructured Bi₂Se₃-Decorated TiSe₂ Pyramids on Ti Foil for Photoelectrochemical Water Splitting

The interface of two-dimensional transition metal dichalcogenides hosts collective interactions between the electronic structures that tune the charge density wave (CDW) states and the photoelectrochemical (PEC) properties of heterostructures. This work reports the influence of the interface on the CDW and PEC of a sputtered Bi 2 Se 3 /TiSe 2 heterostructure on Ti metal foils. The hexagonal nanoflakes on the spiral-pyramid-like surface morphology of pristine TiSe 2 confirm the Bi 2 Se 3 decoration on the TiSe 2 sample. The stoichiometric growth of TiSe 2 and Bi 2 Se 3 was revealed from X-ray photoelectron spectroscopy and Raman spectroscopy. The temperature-dependent Raman spectroscopy demonstrates the evolution of E g CDW and A 1g CDW optical phonon modes with increased CDW phase transition temperature for the Bi 2 Se 3 /TiSe 2 heterostructure. The enhancement of photoresponsive properties of the Bi 2 Se 3 /TiSe 2 heterostructure under a solar light intensity of 100 mW/cm 2 (AM = 1.5 G) in 0.5 M Na 2 SO 4 electrolyte solution toward suitable water splitting was validated from the PEC measurements. This engineered heterostructure can pave the futuristic path to studying light-active electrodes with tunable CDW properties of pristine TiSe 2 and Bi 2 Se 3 /TiSe 2 heterostructures grown on flexible Ti substrates.