A Visible Light-Driven α-MnO₂/UiO-66-NH₂ S-Scheme Photocatalyst toward Ameliorated Oxy-TCH Degradation and H₂ Evolution

Abstract

Photocatalytic hydrogen production and pollutant degradation using a heterogeneous photocatalyst remains an alternative route for mitigating the impending pollution and energy crisis. Hence, the development of cost-effective and environmentally friendly semiconducting materials with high solar light captivation nature is imperative. To overcome this challenge, α-MnO 2 nanorod (NR)-modified MOF UiO-66-NH 2 (UNH) was prepared via a facile solvothermal method, which is efficient toward H 2 evolution and oxy-tetracycline hydrochloride (O-TCH) degradation. The field-emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HR-TEM) results of the α-MnO 2 @UNH (MnU) hybrid reveals its nanorod embedded in MOF matrix, and the X-ray photoelectron spectroscopy (XPS) result confirms the interaction of UNH moiety with α-MnO 2 NRs. Additionally, the outstanding separation of photogenerated excitons and the charge-transfer efficacy are further validated by photoluminescence (PL), time-resolved photoluminescence (TRPL), electrochemical impedance spectroscopy (EIS), and transient photocurrent analysis, which are the key causes for photoactivity augmentation in the MnU composites. The MnU-2 composite shows a superior O-TCH degradation efficiency of 93.23% and an excellent H 2 production rate of about 410.6 μmol h −1 upon light irradiation. This study provides significant evidence in favor of the suggested mediator-free S-scheme-adapted charge migration path, and it effectively explains the enhanced exciton separation leading to extraordinary catalytic efficiency of the proposed composite.

A Comprehensive Review of Ammonium Ion Hybrid Supercapacitors: Exploring Recent Breakthroughs and Future Horizons

“…The pseudocapacitance mechanism is a special energy storage behavior that seems to be capacitive, but it mostly operates on the charge transfer between the electrode–electrolyte interface through a redox reaction . Pseudocapacitors employ electrode materials such as transition metals based oxides/sulfides/hydroxides, metal–organic frameworks (MOFs), MXenes, conducting polymers, as well as heteroatom doped carbon nanostructures, where charge is stored through Faradaic processes involving rapid and reversible redox reactions occurring on the surface or within a few nanometers inside the electrode material. − Considering the pseudocapacitance mechanism, we can classify them as redox pseudocapacitance and intercalation pseudocapacitance, reliant on the redox charge-transfer reactions. Diverse Faradaic-type charge storage mechanisms of these classes of materials include redox reactions, but all Faradaic processes could not be assigned to pseudocapacitive charge storage.…”

Twinned crystal Cd0.9Zn0.1S/MoO3 nanorod S-scheme heterojunctions as promising photocatalysts for efficient hydrogen evolution

“…Different from traditional type II heterojunctions, the S-scheme heterojunctions can maintain highly active holes and electrons and thus exhibit much higher photocatalytic activities. 25–28 More specifically, the photogenerated electrons and holes are retained in the valence band (VB) of OP and the conduction band (CB) of RP, allowing the participation of strong oxidation holes and reduction electrons in the subsequent photocatalytic reactions. 29,30…”