Visible-Light-Active Triazine–Thiadiazole-Based p-Type Copolymer with Stable Photoelectrochemical Behavior in Acidic Electrolytes

Abstract

Design and development of visible-light-active electrode materials with efficient charge separation and enhanced stability are the main criteria for solar energy conversion in photoelectrochemical devices. Herein, we report a new metal-free photoactive polymer containing thiadiazole and triazine units with a stable photo-electroactivity in strong acidic electrolytes. The reactivity of chloro groups in cyanuric chloride and the nucleophilic substitution with 2,5-dimercapto-1,3,5-thiadiazole favors the facile (electro)copolymerization at lower oxidative potentials. Spectral investigations reveal the systematic bathochromic shift toward the visible region with extensive polymerization. X-ray photoelectron spectroscopy, NMR, Raman, IR, and UV−vis spectral studies evidence the substitution of chloro units with dimercapto units. This Nand S-rich poly(2,5-dimercaptothiadiazole-triazine) exhibits p-type photoactivity with the optical band gaps in the range of 2.4− 2.6 eV. On the contrary, poly-2,5-dimercaptothiadiazole displays poor n-type photoactivity. The photoelectrode shows stable, repeatable photovoltage (15−20 mV) and photocurrent (3−4 μA cm −2 ) responses in acidic electrolytes, and the incremental photocurrent responses at higher cathodic potentials for longer duration are attributed to the excellent protonation capability of polymeric units. Furthermore, they exhibit good oxygen reduction reaction electrocatalysis.

Interface-Driven Multifunctionality in Two-Dimensional TiO2 Nanosheet/Poly(Dimercaptothiadiazole-Triazine) Hybrid Resistive Random Access Memory Device

“…More details about the positions of Raman peaks can be found in the Supporting Information. 33,34 3.2. Resistive Switching by DC and AC Measurements.…”

“…It is reported that the protonation effect can improve the photoelectroactivity of the Poly(DMcT-CC) polymer. 33,35 IS measurements carried out on these devices show a single semicircle in both the biases. The model circuit and fitting of IST measurements are presented in the Supporting Information Figure S6e.…”

“…Poly(DMcT-CC) polymer solution was obtained by chemical synthesis route from 2,5dimercapto-1,3,4-thiadiazole (0.02 M) and cyanuric chloride (0.01 M) in Na 2 SO 4 (20 mL of 0.5 M) and acetonitrile solution. 33 2.3. Device Fabrication.…”

“…Moreover, it is known that the shift toward visible range depends on the extent of polymerization. 33 The I−V measurements carried out at low bias by sweeping voltage from −60 to 60 mV, both under dark and UV illumination conditions, are shown in Figure 4b. At 50 mV, it is observed that the hybrid device exhibits UV sensing properties wherein, the current nearly increases by three times of dark current upon illumination due to the generation of electronhole pairs as in the case of usual light sensors.…”

Construction of a Dye-Sensitized and Gold Plasmon-Enhanced Cathodic Photoelectrochemical Biosensor for Methyltransferase Activity Assay

“…p-Type semiconductors can function as photocathodes, and they interact with electron acceptors instead of electron donors, efficiently resisting the reductive agents and photocorrosion . Recently, the p-type semiconductors have attracted more and more attention in the development of cathodic PEC sensors. − Polymer compounds such as triazine–thiadiazole-based copolymers, arylacetylene-based copolymers, and polythiophene exhibit p-type semiconductor properties, with promising applications in energy conversion and active photocathodes . Covalent organic polymers (COPs) are porous polymer compounds with the characteristics of large specific surface area, good stability, adjustable function, and controllable structure and have been widely applied in drug delivery, , catalysis, gas storage/separation, − sensing, and energy storage .…”