A multifunctional Ni-doped iron pyrite/reduced graphene oxide composite as an efficient counter electrode for DSSCs and as a non-enzymatic hydrogen peroxide electrochemical sensor

Synergistic effect of novel pyrite/N-doped reduced graphene oxide composite with heterojunction structure for enhanced photo-assisted reduction of Cr(VI) in oxic water: Specific role of molecular oxygen

To avoid severe aggregation and synergistically utilize the intrinsic and photocatalytic reducibility, pyrite (FeS2) was loaded onto N-doped reduced graphene oxides (N-rGO) to fabricate a novel FeS2/N-rGO heterojunction catalyst for enhanced chromium (Cr(VI)) reduction in oxic condition to simultaneously investigate the specific effect and role of dissolved oxygen (DO). Characterization results showed that strong interaction and combination of FeS2 and N-rGO not only achieved the uniform distribution of FeS2, but also increased the defects, and exposed more functional groups. Meanwhile, the Type II heterojunction was formed in FeS2/N-rGO, which facilitated the separation efficiency of photo-generated carriers and electrons, endowing FeS2/N-rGO a superior photocatalytic activity. Cr(VI) was almost completely reduced via FeS2/N-rGO within 60 min under irradiation (Cr(VI) = 10 mg/L, dosage = 0.2 g/L), 3 times that of pristine FeS2 (18.7 %). Trapping and Electron Spin Resonance (ESR) experiments indicated that photo-generated e- and derived O2- species from photoactivation of dioxygen (DO) were the key reactive species for the enhancement of photo-assisted Cr(VI) reduction, rather than reductive Fe2+ and S22- species. Although the photocatalysis of FeS2/N-rGO cannot directly generate hydroxyl radicals (OH), the oxidative OH ascribed to superoxide radicals (O2-), photo-induced holes and free DO preferentially consumed by Fe2+ and S22- with stronger reducibility. Hence, as compared to the anoxic condition, the reduction rate of Cr(VI) was slightly decreased, but still could be totally removed within 60 min in the oxic conditions. Due to the excessive amount of FeS2/N-rGO, Cr(III) after reduction would not be influenced by oxidative species and maintain stability under oxic condition. This study provided a facile modification strategy for FeS2 based composites and uncovered its working mechanism for Cr(VI) decontamination.

Sn species modified mesoporous zeolite TS-1 with oxygen vacancy for enzyme-free electrochemical H2O2 detecting

Sn species modified zeolite TS-1 with a unique mesopore structure (Sn-TS-1) and rich oxygen vacancy defects has been designed via a sol-gel method and an ion-exchange process, which can be used as an enzyme-free electrochemical sensor for H₂O₂ detection. The resultant composite Sn-TS-1 has a high BET surface area of 191 cm² g^-1, fast electron transfer, rich oxygen vacancies, and abundant active sites, showing super performance in H₂O₂ reduction with a low detection limit (0.27 μM, S/N = 3). The current is linear with H₂O₂ concentration from 1 to 1000 and 1000 to 11 000 μM, and the corresponding sensitivities are 360.4 and 80.44 μA mM^-1 cm^-1, respectively. More importantly, this Sn-TS-1 sensor also shows excellent anti-interference ability and stability. This work provides a new idea for an enzyme-free sensor for H₂O₂ detection in biological environments, which has promising potential in point-of-care (POC) testing for H₂O₂.

Tuning up the photovoltaic performances upon the utility of diketopyrrolopyrrole in PEO-based gel polymer electrolytes

The role of diketopyrrolopyrrole (DPP-H) as an additive on the ionic conductivity of poly(ethylene oxide) (PEO)-based gel polymer electrolytes (GPE) was studied for DSSC applications. The pure PEO/PC/KI/TPAI/I2 GPE was prepared with a mixture of propylene carbonate (PC) as a non-volatile plasticizer and iodide salts, such as potassium iodide (KI), tetrapropylammonium iodide (TPAI) and iodine (I2), together with PEO. The modified GPEs were prepared with different weight percentage (wt%) ratios (0.5%, 0.75%, 1% and 1.25%) of DPP-H using acetonitrile as a solvent. The polymer gel electrolytes were characterized by X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FTIR), and the electrochemical properties were analyzed to relate the nature of the polymer and iodine ion conducting properties. The pure PEO/PC/TPAI/KI/I2 electrolyte exhibited an ionic conductivity value of 0.084 mS·cm-1 at room temperature. Upon the optimized addition of DPP-H (0.75 wt%), the ionic conductivity was found to be improved to a maximum value of 0.393 mS·cm-1, and the highest diffusion coefficient of 1.02 × 10-6 cm2 s-1 was observed. The optimized GPEs photovoltaic characterization studies showed higher power conversion efficiency (PCE) of 6.69% for DSSC under light illumination intensity of 100 mW cm-2. The same was compared with pure electrolyte, which delivered PCE of 4.39%. To gain an in-depth understanding of the interfacial resistance of the fabricated devices, the electron lifetime and transient photo response was analyzed. These above studies showed that prepared GPE could be an efficient alternative for traditional DSSCs with liquid electrolyte.

Design and fabrication of cost-effective and sensitive non-enzymatic hydrogen peroxide sensor using Co-doped δ-MnO2 flowers as electrode modifier

The development of a cost-effective and highly sensitive hydrogen peroxide sensor is of great importance. Electrochemical sensing is considered the most sensitive technique for hydrogen peroxide detection. Herein, we reported a cost-effective and highly sensitive hydrogen peroxide sensor using Co-doped δ-MnO₂ (Co@δ-MnO₂) flower-modified screen-printed carbon electrode. The δ-MnO₂ and Co@δ-MnO₂ flowers were synthesized by employing a hydrothermal approach. Advanced techniques such as PXRD, SEM, FTIR, Raman, UV, EDX, BET, and TEM were utilized to confirm the formation of δ-MnO₂ and Co-doped δ-MnO₂ flowers. The fabricated sensor exhibited an excellent detection limit (0.12 μM) and sensitivity of 5.3 μAμM^-1 cm^-2.Graphical abstract.