Synthesis of Pt nanoparticles supported on a novel 2D bismuth tungstate/lanthanum titanate heterojunction for photoelectrocatalytic oxidation of methanol

Two-Dimensional Layered Heterojunctions for Photoelectrocatalysis

Two-dimensional (2D) layered nanomaterial heterostructures, arising from the combination of 2D materials with other low-dimensional species, feature a large surface area to volume ratio, which provides a high density of active sites for catalytic applications and for (photo)electrocatalysis (PEC). Meanwhile, their electronic band structure and high electrical conductivity enable efficient charge transfer (CT) between the active material and the substrate, which is essential for catalytic activity. In recent years, researchers have demonstrated the potential of a range of 2D material interfaces, such as graphene, graphitic carbon nitride (g-C3N4), metal chalcogenides (MCs), and MXenes, for (photo)electrocatalytic applications. For instance, MCs such as MoS2 and WS2 have shown excellent catalytic activity for hydrogen evolution, while graphene and MXenes have been used for the reduction of carbon dioxide to higher value chemicals. However, despite their great potential, there are still major challenges that need to be addressed to fully realize the potential of 2D materials for PEC. For example, their stability under harsh reaction conditions, as well as their scalability for large-scale production are important factors to be considered. Generating heterojunctions (HJs) by combining 2D layered structures with other nanomaterials is a promising method to improve the photoelectrocatalytic properties of the former. In this review, we inspect thoroughly the recent literature, to demonstrate the significant potential that arises from utilizing 2D layered heterostructures in PEC processes across a broad spectrum of applications, from energy conversion and storage to environmental remediation. With the ongoing research and development, it is likely that the potential of these materials will be fully expressed in the near future.

La2Ti2O7 nanosheets modified by Pt quantum dots for efficient NO removal avoiding NO2 secondary pollutant

Two-dimensional La₂Ti₂O₇ nanosheets with regular morphology and good dispersion were prepared by the hydrothermal method under a magnetic field. Zero-dimensional Pt quantum dots (Pt-QDs) were loaded on the La₂Ti₂O₇ nanosheets. The electron-hole separation and carrier transfer in the Pt-loaded La₂Ti₂O₇ nanosheets were significantly enhanced. The La₂Ti₂O₇ nanosheets loaded with 3 wt% Pt-QDs exhibit the largest NO removal efficiency of 51% and less than 3.2 ppb NO₂ intermediate pollutant in 30 min. The high photocatalytic ability was attributed to the surface plasmon resonance in Pt-QDs and the enhanced electron-hole separation. A large number of e^-, h⁺, •OH and •O₂^- active species were formed on the surface of Pt-loaded La₂Ti₂O₇ nanosheets under light irradiation. The conversion pathway from NO to NO₃^- was verified by the in situ diffuse reflectance infrared Fourier-transform spectroscopy and DFT calculation. This work supplies a feasible approach to responsive photocatalysts for efficient, stable, and selective NO removal avoiding the NO₂ secondary pollutant.

Enhancement of photoelectrocatalytic performance of copper cobaltate nanoflowers modified with 5,10,15,20-tetrakis(4-carboxylphenyl)porphyrin for methanol oxidation under light

With the continuously increasing global energy demand, there is an urgent requirement to find efficient methanol oxidation reaction (MOR) catalysts that can replace precious metals. In this work, we have elaborately integrated 5,10,15,20-tetrakis(4-carboxyphenyl) porphyrin (H₂TCPP) with copper cobaltate (CuCo₂O₄), which possesses efficient separation of photogenerated charges and increased active sites. The mass activity of H₂TCPP/CuCo₂O₄ (534.75 mA mg^-1) toward MOR is higher than that of pure CuCo₂O₄ (291.75 mA mg^-1) under light. In addition, H₂TCPP/CuCo₂O₄ can catalyze the oxidation of other alcohols, such as ethanol, ethanediol, isopropanol, and glycerol. This study demonstrates that it is feasible to enhance the MOR activity by the modification of bimetallic transition metal oxides with porphyrins.

Reline deep eutectic solvent mediated synthesis of lanthanum titanate for heavy metal remediation and photocatalytic degradation

Toxic heavy metal and dye contamination are potential threats that mutilate the essential triad of life; air, water and soil. Despite commercial applicability and importance, the over accumulation of these noxious toxicants has become a disturbing concern. As a result, their remediation has drawn greater fascination leading to the inexplicable quest for a material which can act as both an adsorbent and as a photocatalyst. The present work highlights a novel solid-state technique assisted with reline (Choline chloride: Urea) deep eutectic solvent for the synthesis of lanthanum titanate. The synthesized material was established with physical characterizations like PXRD, FT-IR, UV-DRS, BET, XPS, HR-SEM and TEM techniques. Further, the ruptured petal-like lanthanum titanate was integrated as an adsorbent for the removal of lead (Pb), arsenic (As) and chromium (Cr) heavy metals. The adsorbent presented increased adsorption efficiencies of 96, 74 and 71% towards Pb, As and Cr respectively. Dependence of the degradation efficiency over concentration, pH, contact time and competitive environments were analyzed and inferred. Furthermore, lanthanum titanate was used for the photocatalytic degradation of reactive black (RB5), red (RR198) and yellow (RY145) dyes. The degradation efficiencies were found to be 68.31, 85.2 and 96.8% for RB5, RR198 and RY145 dyes respectively. Variation in concentration and pH of the dye solutions were examined and reaction kinetics was also proposed. In conclusion, the as synthesized lanthanum titanate is assured to play dual roles as a versatile cost-effective adsorbent for the remediation of heavy metals and as a potential candidate for photocatalytic degradation.

Synergistic catalytic hydrolysis of ammonia borane to release hydrogen over AgCo@CN

Synergistic catalytic AB hydrolysis to generate hydrogen was achieved over AgCo@CN synthesized by auto-reduction between Co@CN and a Ag precursor.

Rod-like MnO2 boost Pd/reduced graphene oxide nanocatalyst for ethylene glycol electrooxidation

Anode catalyst is one of the core components of fuel cell, but its poor catalytic activity, short lifespan, and high price are tricky problems to the commercialization of fuel cell. Herein, a novel rod-like MnO₂ decorated reduced graphene oxide (RGO) supported Pd hybrid (Pd/RGO-MnO₂) has been designed, which manifests more negative onset oxidation potential, higher peak current density, and better long-term stability relative to Pd/RGO and pure Pd catalysts when serving for ethylene glycol electrooxidation. This enhancement may be due to the addition of MnO₂, which can effectively promote the adsorption of hydroxyl at a lower potential and produce a strong electronic interaction with Pd, as confirmed by X-ray photoelectron spectroscopy (XPS) technique. In view of its excellent performance and low cost, Pd/RGO-MnO₂ is considered to be a potential and effective anode catalyst for DEGFCs.

Multi-dimensional collaboration promotes the catalytic performance of 1D MoO3 nanorods decorated with 2D NiS nanosheets for efficient water splitting

The ability to manipulate heterostructures is of great importance to achieve high-performance electrocatalysts for direct water-splitting devices with excellent activity toward hydrogen production. Herein, a novel top-down strategy involving the in situ transformation of one-dimensional MoO3 nanorod arrays grafted with two-dimensional NiS nanosheets supported on a three-dimensional nickel foam skeleton is proposed. Namely, a heterostructured electrocatalyst on the Ni foam skeleton containing MoO3 nanorod arrays decorated with NiS nanosheets is synthesized by a facile hydrothermal method followed by one-step sulfidation treatment. Experimental analysis confirmed that this novel composite has the merits of a large quantity of accessible active sites, unique distribution of three different spatial dimensions, accelerated mass/electron transfer, and the synergistic effect of its components, resulting in impressive electrocatalytic properties toward the hydrogen evolution reaction and oxygen evolution reaction. Furthermore, an advanced water-splitting electrolyzer was assembled with NiS/MoO3/NF as both the anodic and cathodic working electrode. This device requires a low cell voltage of 1.56 V to afford a water-splitting current density of 10 mA·cm-2 in basic electrolyte, outperforming previously reported electrocatalysts and even state-of-the-art electrocatalysts. More significantly, this work provides a way to revolutionize the design of heterostructured electrocatalysts for the large-scale commercial production of hydrogen using direct water-splitting devices.