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Group 10 transition metal dichalcogenide PtSe2 has drawn considerable attention toward the search for an efficient visible light photocatalyst due to its strong light–matter interaction nature. Here we report PtSe2/TiO2 heterostructure for solar energy conversion through photoelectrochemical (PEC) water splitting. The PtSe2/TiO2 heterostructure was prepared by sputtered Pt film followed by the chemical vapor deposition method. Raman spectroscopy and X-ray diffraction analysis confirmed the growth of hexagonal phase PtSe2 and anatase TiO2 corresponding to their distinguished peak characteristics. The field-emission scanning electron microscopy and transmission electron microscopy studies reveal that TiO2 nanotubes were decorated with PtSe2 nanoflakes forming PtSe2/TiO2 heterostructure. The chemical composition of the prepared samples was studied by using the X-ray photoelectron spectroscopy and indicated the sole presence of PtSe2 and TiO2 compounds. The PEC measurements were taken in 0.5 M Na2SO4 electrolyte solution under simulated sunlight (AM = 1.5 G). The maximum photocurrent density of ~ 234.7 µA/cm2 at 1.4 V versus RHE was recorded for PtSe2/TiO2 heterostructure, which is 1.7 times higher than that of Pt/TiO2. The improved PEC performance of PtSe2/TiO2 as a result of efficient solar absorption over a wider spectrum and effective charge separation produced by type-II band alignment between PtSe2 and TiO2. [ABSTRACT FROM AUTHOR]

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 Bi2Se3/TiSe2 heterostructure on Ti metal foils. The hexagonal nanoflakes on the spiral-pyramid-like surface morphology of pristine TiSe2 confirm the Bi2Se3 decoration on the TiSe2 sample. The stoichiometric growth of TiSe2 and Bi2Se3 was revealed from X-ray photoelectron spectroscopy and Raman spectroscopy. The temperature-dependent Raman spectroscopy demonstrates the evolution of EgCDW and A1gCDW optical phonon modes with increased CDW phase transition temperature for the Bi2Se3/TiSe2 heterostructure. The enhancement of photoresponsive properties of the Bi2Se3/TiSe2 heterostructure under a solar light intensity of 100 mW/cm2 (AM = 1.5 G) in 0.5 M Na2SO4 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 TiSe2 and Bi2Se3/TiSe2 heterostructures grown on flexible Ti substrates. [ABSTRACT FROM AUTHOR]

ZnCo2O4 has been studied as an electrode material for supercapacitor applications because of its excellent redox activity. It is known that morphology plays an important role in deciding the electrochemical behavior of material through factors such as specific surface area and active surface states. Surfactant plays a significant role in determining the morphology and hence surface area of the material. Here, we present an extensive comparative study on the effect of two surfactants, urea and hexamethylenetetramine (HMTA), on the morphology of ZnCo2O4 and its impact on both supercapacitor and oxygen evolution reaction (OER) performance. Synthesis of ZnCo2O4 using urea yields urchin-like morphology, which exhibits a specific capacity of 94 mAh g−1 at 2 A g−1 , which is much higher than the 34 mAh g−1 achieved through hexagonal sheet-type morphology obtained from HMTA as a surfactant. We fabricated a coin cell with the urea-derived material, which shows an energy density of 19 W h kg−1, a power density of 4125 W kg−1 , and a Coulombic efficiency of 97%. Further, a comparative study of OER for both types of morphology yields a lower overpotential of 336 mV for urea-derived urchin morphology compared to 362 mV for the HMTA-based sample. Other electrochemical parameters, such as Tafel slope, double-layer capacitance, and turn-over frequency, are also evaluated for both types of morphology. The better overall performance of urea-based urchin-like morphology is attributed to higher specific surface area and oxygen vacancies, as confirmed through Brunauer–Emmett–Teller (BET) and x-ray photoelectron spectroscopy (XPS). [ABSTRACT FROM AUTHOR]