Visible Light-Driven H2 Production over Highly Dispersed Ruthenia on Rutile TiO2 Nanorods

A review of functions and mechanisms of clay soil conditioners and catalysts in thermal remediation compared to emerging photo-thermal catalysis

High temperatures and providing sufficient time for the thermal desorption of persistent organic pollutants (POPs) from contaminated clay soils can lead to intensive energy consumption. Therefore, this article provides a critical review of the potential additives which can improve soil texture and increase the volatility of POPs, and then discusses their enhanced mechanisms for contributing to a green economy. Ca-based additives have been used to reduce plasticity of bentonite clay, absorb water and replenish system heat. In contrast, non-Ca-based additives have been used to decrease the plasticity of kaolin clay. The soil structure and soil plasticity can be changed through cation exchange and flocculation processes. The transition metal oxides and alkali metal oxides can be applied to catalyze and oxidize polycyclic aromatic hydrocarbons, petroleum and emerging contaminants. In this system, reactive oxygen species (•O2- and •OH) are generated from thermal excitation without strong chemical oxidants. Moreover, multiple active ingredients in recycled solid wastes can be controlled to reduce soil plasticity and enhance thermal catalysis. Alternatively, the alkali, nano zero-valent iron and nano-TiN can catalyze hydrodechlorination of POPs under reductive conditions. Especially, photo and photo-thermal catalysis are discussed to accelerate replacement of fossil fuels by renewable energy in thermal remediation.

Encapsulating stable perovskite catalysts in hollow nanoreactors for enhanced pollutants degradation

Creating a microenvironment for enhanced peroxymonosulfate (PMS) activation is vital in advanced oxidation processes. The objective of this study was to fabricate nanoshells composed of titanium dioxide embedded with cobalt titanate nanoparticles of perovskite to act as nanoreactors for effectively initiating PMS and degrading contaminants. The unique porous structure and confined space of the nanoreactor facilitated reactant absorption and mass transfer to the active sites, resulting in exceptional catalytic performance for pollutant elimination. Experimental findings revealed close to 100% decomposition efficiency of 4-chlorophenol (4-CP) within an hour utilizing the nanoreactors over a wide pH range. The TiO2/CoTiO3 hollow nanoshells catalysts also displayed adaptability in disintegrating organic dyes and antibiotics. The radicals SO4•-, •OH, and non-radicals 1O2 were determined to be accountable for eliminating pollutants, as supported by trapping experiments and electron paramagnetic resonance spectra. The catalyst was confirmed as an electron donor and PMS as an electron acceptor through electrochemical tests and density functional theory calculations. This study underscores the potential of incorporating stable perovskite catalysts in hollow nanoreactors to enhance wastewater treatment.

Atomically Dispersed Ru-doped Ti4O7 Electrocatalysts for Chlorine Evolution Reaction with a Universal Activity

Chlorine has been supplied by the chlor-alkali process that deploys dimensionally stable anodes (DSAs) for the electrochemical chlorine evolution reaction (ClER). The paramount bottlenecks have been ascribed to an intensive usage of precious elements and inevitable competition with the oxygen evolution reaction. Herein, a unique case of Ru2+-O4 active motifs anchored on Magnéli Ti4O7 (Ru-Ti4O7) via a straightforward wet impregnation and mild annealing is reported. The Ru-Ti4O7 performs radically active ClER with minimal deployment of Ru (0.13 wt%), both in 5 m NaCl (pH 2.3) and 0.1 m NaCl (pH 6.5) electrolytes. Scanning electrochemical microscopy demonstrates superior ClER selectivity on Ru-Ti4O7 compared to the DSA. Operando X-ray absorption spectroscopy and density functional theory calculations reveal a universally active ClER (over a wide range of pH and [Cl-]), through a direct adsorption of Cl- on Ru2+-O4 sites as the most plausible pathway, together with stabilized ClO* at low [Cl-] and high pH.

Enhancing Ru-Cl interaction via orbital hybridization effect in Ru0.4Sn0.3Ti0.3 electrode for efficient chlorine evolution

Chlorine evolution reaction (CER) is a commercially valuable electrochemical reaction used at an industrial scale. However, oxygen evolution reaction (OER) during the electrolysis process inevitably leads to the decreased efficiency of CER. It is necessary to improve the selectivity of CER by minimizing or even eliminating the occurrence of OER. Herein, a ternary metal oxide (Ru0.4Sn0.3Ti0.3) electrode was fabricated and employed as an active and robust anode for CER. The Ru0.4Sn0.3Ti0.3 electrode exhibits an excellent CER performance in 6.0 M NaCl solution, with a low potential of 1.17 V (vs. saturated calomel electrode, SCE) at 200 mA cm-2 current density, a high Cl2 selectivity of over 90 %, and robust durability after consecutive operation for 160 h under 100 mA cm-2. The maximum O2-Cl2 potential difference between OER and CER further demonstrates the high Cl2 selectivity of Ru0.4Sn0.3Ti0.3 electrode. Theoretical studies show that the strong Ru 3d-Ti 3d orbitals hybridization effect makes the d-band center (εd) of Ru 3d and Ti 3d orbitals positively and negatively shifted, respectively, endowing Ru site with enhanced Cl adsorption ability (i.e. enhanced Ru-Cl interaction) and Ru0.4Sn0.3Ti0.3 electrode with superior CER activity. This work offers valuable insights into the development of advanced electrodes for CER in practical application.

Photocatalytic hydrogen evolution over Pt–Pd dual atom sites anchored on TiO2 nanosheets

The defective TiO2 nanosheets (Vo-TiO2) supported dual atomic catalyst (Pt–Pd SAs/Vo-TiO2) to product hydrogen.

Surface hybridization of π-conjugate structure cyclized polyacrylonitrile and radial microsphere shaped TiO2 for reducing U(VI) to U(IV)

It is still a challenge to obtain uranium (U) adsorbents with high selectivity, excellent cycle stability and excellent performance through design and synthesis. In this paper, the TiO₂/CPAN-AO catalyst was prepared by the hydrothermal method combined with high temperature cyclization dehydrogenation. TiO₂/CPAN-AO has excellent photocatalytic properties, which can reduce U(VI) to U(IV) quickly and selectively. The generated Z-type heterojunction promotes the reduction ability of photogenerated electrons, and obtains great selectivity to UO₂²⁺ (Uranyl ions) through the AO group. TiO₂/CPAN-AO with π-electron conjugated structure broadens the spectral range through surface hybridization and prolongs the lifetime of photo-generated charges. Under the induction of light, the uranium extraction capacity of TiO₂/CPAN-AO after 5 h of irradiation is about 2.38 g/g. TiO₂/CPAN-AO is a catalyst with enhanced adsorption capacity, making it possible to extract uranium from large-scale natural seawater in the future.

Noble-metal-free hexagonal wurtzite CdS nanoplates with exposed (110) and (112) crystal facets for efficient visible-light H2 production

Hexagonal wurtzite CdS has been regarded as one of the most promising semiconductors for photocatalysis.

Surface domain heterojunction on rutile TiO2 for highly efficient photocatalytic hydrogen evolution

Compared with the highly active anatase TiO2, rutile TiO2 usually presents poor photocatalytic performance due to high electron-hole recombination. Herein, we propose a surface domain heterojunction (SDH) structure between adjacent micro-domains with and without chemisorbed chlorine on rutile TiO2, which utilizes the potential difference between these domains to form a built-in field that promotes charge separation. Single-crystal rutile TiO2 nanorods assembled into radial microspheres with SDHs were fabricated, and these exhibited excellent solar-driven photocatalytic hydrogen evolution, ∼8-fold higher than that of the pristine one. Experimental results and density functional theory calculations reveal that the exceptional photocatalytic performance can be attributed to the in situ formation of chemisorbed chlorine, which forms SDHs that separate electrons and holes efficiently and results in surface reconfiguration, exposing the tri-active sites, increasing the O-site active centers and enhancing the catalytic activity of the 4-coordinated (Ti4c) and 5-coordinated Ti sites (Ti5c). This SDH strategy can extend to other halogen elements and thus provides an universal approach for the rational design of high-efficiency TiO2 photocatalysts toward sustainable solar-fuel evolution.

Engineering Interface with a One-Dimensional RuO2/TiO2 Heteronanostructure in an Electrocatalytic Membrane Electrode: Toward Highly Efficient Micropollutant Decomposition

Decomposition of micropollutants using an electrocatalytic membrane reactor is a promising alternative to traditional advanced oxidation processes due to its high efficiency and environmental compatibility. Rational interface design of electrocatalysts in the membrane electrode is critical to the performance of the reactor. We herein developed a three-dimensional porous membrane electrode via in situ growth of one-dimensional RuO₂/TiO₂ heterojunction nanorods on a carbon nanofiber membrane by a facile hydrothermal and subsequent thermal treatment approach. The membrane electrode was used as the anode in a gravity-driven electrocatalytic membrane reactor, exhibiting a high degradation efficiency of over 98% toward bisphenol-A and sulfadiazine. The superior electrocatalytic performance was attributed to the 1D RuO₂/TiO₂ heterointerfacial structure, which provided the fast electron transfer, high generation rate of the hydroxyl radical, and large effective surface area. Our work paves a novel way for the fundamental understanding and designing of novel highly effective and low-consumptive electrocatalytic membranes for wastewater treatment.

A size tunable bimetallic nickel-zinc nitride as a multi-functional co-catalyst on nitrogen doped titania boosts solar energy conversion

To enable high-efficiency solar energy conversion, rational design and preparation of low cost and stable semiconductor photocatalysts with associated co-catalysts are desirable. However preparation of efficient catalytic systems remains a challenge. Here, N-doped TiO2/ternary nickel-zinc nitride (N-TiO2-Ni3ZnN) nanocomposites have been shown to be a multi-functional catalyst for photocatalytic reactions. The particle size of Ni3ZnN can be readily tuned using N-TiO2 nanospheres as the active support. Due to its high conductivity and Pt-like properties, Ni3ZnN promotes charge separation and transfer, as well as reaction kinetics. The material shows co-catalytic performance relevant for multiple reactions, demonstrating its multifunctionality. Density functional theory (DFT) based calculations confirm the intrinsic metallic properties of Ni3ZnN. N-TiO2-Ni3ZnN exhibits evidently improved photocatalytic performances as compared to N-TiO2 under visible light irradiation.

Assembling of Bi atoms on TiO2 nanorods boosts photoelectrochemical water splitting of semiconductors

Low photoconversion efficiency, high charge transfer resistance and fast recombination rate are the bottlenecks of semiconductor nanomaterials in photoelectrochemical (PEC) water splitting, where the introduction of an appropriate co-catalyst is an effective strategy to improve their performance. In the present study, we have purposely designed atomic-scale dispersed bismuth (Bi) assembled on titanium dioxide nanorods (TiO2), and demonstrated its effective role as a co-catalyst in enhancing the PEC water splitting performance of TiO2. As a result, functionalized Bi/TiO2 generates a high photocurrent intensity at 1.23 VRHE under simulated solar light irradiation, which is 4-fold higher than that of pristine TiO2, exhibiting a significantly improved PEC performance for water splitting. The strategy presented in this study opens a new window for the construction of non-precious metals dispersed at atomic scales as efficient co-catalysts for realizing sustainable solar energy-driven energy conversion and storage.

Atomic Layer Deposition of an Effective Interface Layer of TiN for Efficient and Hysteresis-Free Mesoscopic Perovskite Solar Cells

Perovskite solar cells (PSCs) have experienced outstanding advances in power conversion efficiencies (PCEs) by employing new electron transport layers (ETLs), interface engineering, optimizing perovskite morphology, and improving charge collection efficiency. In this work, we study the role of a new ultrathin interface layer of titanium nitride (TiN) conformally deposited on a mesoporous TiO₂ (mp-TiO₂) scaffold using the atomic layer deposition method. Our characterization results revealed that the presence of TiN at the ETL/perovskite interface improves the charge collection as well as reduces the interface recombination. We find that the morphology (grain size) and optical properties of the perovskite film deposited on the optimized mp-TiO₂/TiN ETL are improved drastically, leading to devices with a maximum PCE of 19.38% and a high open-circuit voltage (V_oc) of 1.148 V with negligible hysteresis and improved environmental (∼40% RH) and thermal (80 °C) stabilities.

In situ growth of porous TiO2 with controllable oxygen vacancies on an atomic scale for highly efficient photocatalytic water splitting

In situ regulation of oxygen vacancies of porous TiO₂ at atomic scale with promoting photocatalytic efficiency.

Rutile RuxTi1-xO2 nanobelts to enhance visible light photocatalytic activity

We herein report on the synthesis by a facile sol-gel method without templates for preparing rutile Ru_xTi_1-xO₂ (x = 0.16; 0.07; 0.01) nanobelts with exposed (001) facets. The rutile nanobelts with exposure (001) facets, favor the separation photogenerated electron-hole pairs and inhibit the recombination of the electron-hole pairs resulting in the increase of the number of main superoxide and hydroxyl radicals. The photocatalytic properties of the rutile Ru_xTi_1-xO₂ nanobelts were evaluated by discoloring of MB (methylene blue) dye under sunlight irradiation at an intensity of 40000 lx. It was also done a thorough interface analysis to determine the band energy.

Dual Cocatalysts in TiO2 Photocatalysis

Semiconductor photocatalysis is recognized as a promising strategy to simultaneously address energy needs and environmental pollution. Titanium dioxide (TiO₂ ) has been investigated for such applications due to its low cost, nontoxicity, and high chemical stability. However, pristine TiO₂ still suffers from low utilization of visible light and high photogenerated-charge-carrier recombination rate. Recently, TiO₂ photocatalysts modified by dual cocatalysts with different functions have attracted much attention due to the extended light absorption, enhanced reactant adsorption, and promoted charge-carrier-separation efficiency granted by various cocatalysts. Recent progress on the component and structural design of dual cocatalysts in TiO₂ photocatalysts is summarized. Depending on their components, dual cocatalysts decorated on TiO₂ photocatalysts can be divided into the following categories: bimetallic cocatalysts, metal-metal oxide/sulfide cocatalysts, metal-graphene cocatalysts, and metal oxide/sulfide-graphene cocatalysts. Depending on their architecture, they can be categorized into randomly deposited binary cocatalysts, facet-dependent selective-deposition binary cocatalysts, and core-shell structural binary cocatalysts. Concluding perspectives on the challenges and opportunities for the further exploration of dual cocatalyst-modified TiO₂ photocatalysts are presented.

Highly effective ruthenium-doped TiO2nanoparticles photocatalyst for visible-light-driven photocatalytic hydrogen production

This paper reports the synthesis of bare TiO₂and various molar concentrations of ruthenium (Ru)-doped TiO₂nanoparticles by the precipitation method.

Hybrid nanostructures of pit-rich TiO2 nanocrystals with Ru loading and N doping for enhanced solar water splitting

Hybrid nanostructures of pit-rich TiO₂ nanocrystals with ruthenium loading and nitrogen-doping exhibited enhanced solar water splitting.

One-Step Acidic Hydrothermal Preparation of Dendritic Rutile TiO₂ Nanorods for Photocatalytic Performance

Three-dimensional and dendritic rutile TiO₂ nanorods were successfully fabricated on a Ti foil surface using a one-step acidic hydrothermal method. The TiO₂ nanorods were characterized using X-ray diffraction (XRD), energy dispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and optical contact angle testing. The results showed that the nanorods with diameters of 100⁻500 nm and lengths of 100 nm to 1 μm were obtained on the Ti foil surface. The length and density of the TiO₂ nanorods were perfect at the conditions of HCl concentration 0.5 mol/L, temperature 220 °C, and reaction time 12 h. The TiO₂ nanorods formed parallel to the consumption of Ti and grew along the (110) direction having a tetragonal rutile crystal. The morphology of the nanorods possessed a three-dimensional structure. The contact angle of the nanorods was only 13 ± 3.1°. Meanwhile, the photocatalytic activities of the TiO₂ nanorods were carried out using ultraviolet fluorescence spectrophotometry for the methyl orange detection, and the degradation was found to be about 71.00% ± 2.43%. Thus, TiO₂ nanorods can be developed by a one-step acidic hydrothermal method using Ti foil simultaneously as the substrate with a TiO₂ source; the TiO₂ nanorods exhibited photocatalytic performance while being environment-friendly.

Integrating Zeolite-Type Chalcogenide with Titanium Dioxide Nanowires for Enhanced Photoelectrochemical Activity

Developing photoanodes with efficient visible-light harvesting and excellent charge separation still remains a key challenge in photoelectrochemical water splitting. Here zeolite-type chalcogenide CPM-121 is integrated with TiO₂ nanowires to form a heterostructured photoanode, in which crystalline CPM-121 particles serve as a visible light absorber and TiO₂ nanowires serve as an electron conductor. Owing to the small band gap of chalcogenides, the hybrid electrode demonstrates obvious absorption in visible-light range. Electrochemical impedance spectroscopy (EIS) shows that electron transport in the hybrid electrode has been significantly facilitated due to the heterojunction formation. A >3-fold increase in photocurrent is observed on the hybrid electrode under visible-light illumination when it is used as a photoanode in a neutral electrolyte without sacrificial agents. This study opens up a new avenue to explore the potential applications of crystalline porous chalcogenide materials for solar-energy conversion in photoelectrochemistry.

Three-dimensional ruthenium-doped TiO2 sea urchins for enhanced visible-light-responsive H2 production

Ru-doped rutile TiO₂ composed of radially aligned nanorods exhibits good H₂ production from water under visible light irradiation.