H-Glass Supported Hybrid Gold Nano-Islands for Visible-Light-Driven Hydrogen Evolution.

Flat panel reactors, coated with photocatalytic materials, offer a sustainable approach for the commercial production of hydrogen (H2) with zero carbon footprint. Despite this, achieving high solar-to-hydrogen (STH) conversion efficiency with these reactors is still a significant challenge due to the low utilization efficiency of solar light and rapid charge recombination. Herein, hybrid gold nano-islands (HGNIs) are developed on transparent glass support to improve the STH efficiency. Plasmonic HGNIs are grown on an in-house developed active glass sheet composed of sodium aluminum phosphosilicate oxide glass (H-glass) using the thermal dewetting method at 550 °C under an ambient atmosphere. HGNIs with various oxidation states (Au0, Au+, and Au-) and multiple interfaces are obtained due to the diffusion of the elements from the glass structure, which also facilitates the lifetime of the hot electron to be ≈2.94 ps. H-glass-supported HGNIs demonstrate significant STH conversion efficiency of 0.6%, without any sacrificial agents, via water dissociation. This study unveils the specific role of H-glass-supported HGNIs in facilitating light-driven chemical conversions, offering new avenues for the development of high-performance photocatalysts in various chemical conversion reactions for large-scale commercial applications.

Assemble of Bi-doped TiO2 onto 2D MoS2: an efficient p-n heterojunction for photocatalytic H2 generation under visible light.

Fabrication of noble-metal-free, efficient and stable hybrid photocatalyst is essential to address the rapidly growing energy crisis and environmental pollution. Here, MoS2 has been used as the co-catalyst on Bi-doped TiO2 to form a novel heterostructure to increase the utilization of the photogenerated charge carriers for improving photocatalytic H2 evolution activity through water reduction. Significantly increased photocatalytic H2 generation has been achieved on the optimized MoS2/Bi-TiO2 nanocomposite (∼512 µmol g-1) after 4 h of visible light illumination, which is nine times higher than that of the pristine TiO2 (∼57 µmol g-1). The measurements of photocurrent, charge transfer resistance and photo-stability of MoS2/Bi-TiO2 photoanode imply that charge separation efficiency has been improved in comparison to the pure MoS2 and TiO2 photoanodes. Further, the Mott-Schottky study confirmed that a p-n heterojunction has been formed between n-type MoS2 and p-type Bi-doped TiO2, which provides a potential gradient to increase charge separation and transfer efficiency. On the basis of these experimental results, this enhanced photocatalytic activity of MoS2/Bi-TiO2 heterostructures could be ascribed to the significant visible light absorption and the efficient charge carrier separation. Thus, this work demonstrates the effect of p-n junction for achieving high H2 evolution activity and photoelectrochemical water oxidation under visible light illumination.

Role of Efficient Charge Transfer at the Interface between Mixed-Phase Copper-Cuprous Oxide and Conducting Polymer Nanostructures for Photocatalytic Water Splitting.

Photocatalytic hydrogen generation from water splitting is regarded as a sustainable technology capable of producing green solar fuels. However, the low charge separation efficiencies and the requirement of lowering redox potentials are unresolved challenges. Herein, a multiphase copper-cuprous oxide/polypyrrole (PPy) heterostructure has been designed to identify the role of multiple oxidation states of metal oxides in water reduction and oxidation. The presence of a mixed phase in PPy heterostructures enabled an exceptionally high photocatalytic H2 generation rate of 41 mmol h-1 with an apparent quantum efficiency of 7.2% under visible light irradiation, which is a 7-fold augmentation in contrast to the pure polymer. Interestingly, the copper-cuprous oxide/PPy heterostructures exhibited higher charge carrier density, low resistivity, and 6 times higher photocurrent density compared to Cu2O/PPy. Formation of a p-p-n junction between polymer and mixed-phase metal oxide interfaces induce a built-in electric field which influences directional charge transfer that improves the catalytic activity. Notably, photoexcited charge separation and transfer have been significantly improved between copper-cuprous oxide nanocubes and PPy nanofibers, as revealed by femtosecond transient absorption spectroscopy. Additionally, the photocatalyst demonstrates excellent stability without loss of catalytic activity during cycling tests. The present study highlights a superior strategy to boost photocatalytic redox reactions using a mixed-phase metal oxide in the heterostructure to achieve enhanced light absorption, longer charge carrier lifetimes, and highly efficient photocatalytic H2 and O2 generation.

A Ni(II) Metal-Organic Framework with Mixed Carboxylate and Bipyridine Ligands for Ultrafast and Selective Sensing of Explosives and Photoelectrochemical Hydrogen Evolution.

We report a Ni-MOF (nickel metal-organic framework), Ni-SIP-BPY, synthesized by using two linkers 5-sulfoisophthalic acid (SIP) and 4,4'-bipyridine (BPY) simultaneously. It displays an orthorhombic crystal system with the Ama2 space group: a = 31.425 Å, b = 19.524 Å, c = 11.2074 Å, α = 90°, ß = 90°, γ = 90°, and two different types of nickel(II) centers. Interestingly, Ni-SIP-BPY exhibits excellent sensitivity (limit of detection, 87 ppb) and selectivity toward the 2,4,6-trinitrophenol (TNP)-like mutagenic environmental toxin in the pool of its other congeners via "turn-off" fluorescence response by the synergism of resonance energy transfer, photoinduced electron transfer, intermolecular charge transfer, π-π interactions, and competitive absorption processes. Experimental studies along with corroborated theoretical experimentation, vide density functional theory studies, shed light on determining the plausible mechanistic pathway in selective TNP detection, which is highly beneficial in the context of homeland security perspective. Along with the sensing of nitroaromatic explosives, the moderately low band gap and the p-type semiconducting behavior of Ni-SIP-BPY make it suitable as a photoanode material for visible-light-driven water splitting. Highly active surface functionalities and sufficient conduction band minima effectively reduce the water and result in a seven times higher photocurrent density under visible-light illumination.

Highly Active Multimetallic Palladium Nanoalloys Embedded in Conducting Polymer as Anode Catalyst for Electrooxidation of Ethanol.

Fabrication of multimetallic nanocatalysts with controllable composition remains a challenge for the development of low-cost electrocatalysts, and incorporating metal-based catalysts into active carbon nanoarchitectures represents an emerging strategy to improve the catalytic performance of electrocatalysts. Herein, a facile method developed for Pd nanoparticle (NP)-based multimetallic alloys incorporated on polypyrrole (Ppy) nanofibers by in situ nucleation and growth of NPs using colloidal radiolytic technique is described. Electrochemical measurement suggests that the as-prepared catalysts demonstrate dramatically enhanced electrocatalytic activity for ethanol oxidation in alkaline medium. The ultrasmall Pd30Pt29Au41/Ppy nanohybrids (∼8 nm) exhibit excellent electrocatalytic activity, which is ∼5.5 times higher than that of its monometallic counterparts (12 A/mg Pd, 5 times higher activity compared to that of Pd/C catalyst). Most importantly, the ternary nanocatalyst shows no obvious change in chemical structure and long-term stability, reflected in the 2% loss in forward current density during 1000 cycles. The superior catalytic activity and durability of the nanohybrids have been achieved due to the formation of Pt-Pd-Au heterojunctions with cooperative action of the three metals in the alloy composition, and the strong interactions between the Ppy nanofiber support with the metal NPs. The facile synthetic approach provides a new generation of polymer-supported metal alloy hybrid nanostructures as potential electrocatalysts with superior catalytic activity for fuel cell applications.