Controllable Synthesis of Mesoporous TiO₂ Polymorphs with Tunable Crystal Structure for Enhanced Photocatalytic H₂ Production

Abstract

Multiphasic titanium dioxide (TiO2) possessing abundant heterophase junctions have been widely used for various photocatalytic applications. Current synthesis of multiphasic TiO2 mainly involves the process of thermal treatment and multiple steps of rigorous reactions, which is adverse to controlling the crystal phases and phase ratios of multiphasic TiO2. Meanwhile, the resulting products have relatively low surface area and nonporous structure. Here, a facile polymer‐assisted coordination‐mediated self‐assembly method to synthesize mesoporous TiO2 polymorphs with controllable heterophase junctions and large surface area by using polyethylenimine as the porogen in an acidic aqueous synthesis system is reported. Using this approach, the crystal phases (triphase, biphase, and monophase) and phase compositions (0–100%) are easily tailored by selecting the suitable acidic media. Furthermore, the specific surface areas (77–228 m2 g−1) and pore sizes (2.9–10.1 nm) are readily tailored by changing the reaction temperature. The photocatalytic activity of mesoporous TiO2 polymorphs is evaluated by photocatalytic hydrogen evolution. The triphasic TiO2 exhibits an excellent photocatalytic H2 generation rate of 3.57 mmol h−1 g−1 as compared to other polymorphs, which is attributed to the synergistic effects of heterophase junctions and mesostructure. The band diagram of possible electron transfer pathway for triphasic TiO2 is also elucidated.

Hierarchical Porous Molybdenum Carbide Based Nanomaterials for Electrocatalytic Hydrogen Production

“…Wang et al (2018a) synthesized NP-Mo 2 C by direct carbonization. Theoretical calculations show that the doping of heteroatoms into carbon promotes the transfer of electrons in the catalyst, and the heteroatoms may also act as catalytic active sites (Gao et al, 2019;Singh et al, 2019). Owing to the synergistic coupling, the double doping of the N, P heteroatoms in Mo 2 C can remarkably improve the intrinsic activity of each active site.…”

“…Enriched active sites of sufficient unsaturated Mo and C atoms promote intimate contact between the electrolyte and the electrode material, thereby enhancing catalytic performance (Wang et al, 2019a;Cui et al, 2020). The introduction of a suitable matrix to form a strong coupling toward the catalyst can improve the intrinsic catalytic activity of Mo x C, and also increase the conductivity of the catalyst due to the synergistic effect in the hybrid nanostructure, and hance, finally harvest desired electrochemical performance (Amrute1 et al, 2019;Xiong et al, 2019;Zhao et al, 2019c).…”

Controlled Growth and Bandstructure Properties of One Dimensional Cadmium Sulfide Nanorods for Visible Photocatalytic Hydrogen Evolution Reaction

“…Apart from being cost-effective and environmentally benign, the practicability of a semiconductor for targeted applications mostly relies on the solar energy conversion efficiency of the material [4][5][6]. Since Fujishima-Honda reported photoelectrochemical water splitting [7], numerous photocatalysts, such as TiO 2 [8,9], g-C 3 N 4 [10,11], MoS 2 [12,13], ZnIn 2 S 4 [14,15], etc., have been extensively studied for their viability and efficiency in the photocatalyst field. Alternatively, substantial efforts have been made for the development of visible-light-driven photocatalysts, capable of absorbing visible light (≥420 nm) which is about 43% of the solar spectrum.…”

Boosting Visible‐Light‐Driven H2 Evolution of Covalent Triazine Framework from Water by Modifying Ni(II) Pyrimidine‐2‐thiolate Cocatalyst

“…Heterogeneous photocatalysis plays a key role in large‐scale production of renewable H 2 . To date, TiO 2 , [14,15] CdS, [16,17] g‐C 3 N 4 , [10] metal‐organic frameworks [18,19] and covalent‐organic frameworks (COFs) [20,21] are extensively investigated in photocatalytic H 2 evolution under the assistance of Pt, [10,18–22] Pd, [23–25] Ru [26,27] complexes or nanoparticles as cocatalysts, which facilitate charge separation and act as sites for the water reduction into hydrogen [28–31] . Despite the excellent activity of precious transition metals, their low abundance and high cost limit their practical production of solar fuels.…”