BiAg alloy nanospheres: a new photocatalyst for H2 evolution from water splitting

Surface Plasmon Resonance-Mediated Photocatalytic H2 Generation

The limited yield of H2 production has posed a significant challenge in contemporary research. To address this issue, researchers have turned to the application of surface plasmon resonance (SPR) materials in photocatalytic H2 generation. SPR, arising from collective electron oscillations, enhances light absorption and facilitates efficient separation and transfer of electron-hole pairs in semiconductor systems, thereby boosting photocatalytic H2 production efficiency. However, existing reviews predominantly focus on SPR noble metals, neglecting non-noble metals and SPR semiconductors. In this review, we begin by elucidating five different SPR mechanisms, covering hot electron injection, electric field enhancement, light scattering, plasmon-induced resonant energy transfer, and photo-thermionic effect, by which SPR enhances photocatalytic activity. Subsequently, a comprehensive overview follows, detailing the application of SPR materials-metals, non-noble metals, and SPR semiconductors-in photocatalytic H2 production. Additionally, a personal perspective is offered on developing highly efficient SPR-based photocatalysis systems for solar-to-H2 conversion in the future. This review aims to guide the development of next-gen SPR-based materials for advancing solar-to-fuel conversion.

Facile Synthesis of Gram-Scale Mesoporous Ag/TiO2 Photocatalysts for Pharmaceutical Water Pollutant Removal and Green Hydrogen Generation

This work demonstrates a two-step gram-scale synthesis of presynthesized silver (Ag) nanoparticles impregnated with mesoporous TiO₂ and evaluates their feasibility for wastewater treatment and hydrogen gas generation under natural sunlight. Paracetamol was chosen as the model pharmaceutical pollutant for evaluating photocatalytic performance. A systematic material analysis (morphology, chemical environment, optical bandgap energy) of the Ag/TiO₂ photocatalyst powder was carried out, and the influence of material properties on the performance is discussed in detail. The experimental results showed that the decoration of anatase TiO₂ nanoparticles (size between 80 and 100 nm) with 5 nm Ag nanoparticles (1 wt %) induced visible-light absorption and enhanced charge carrier separation. As a result, 0.01 g/L Ag/TiO₂ effectively removed 99% of 0.01 g/L paracetamol in 120 min and exhibited 60% higher photocatalytic removal than pristine TiO₂. Alongside paracetamol degradation, Ag/TiO₂ led to the generation of 1729 μmol H₂ g^-1 h^-1. This proof-of-concept approach for tandem pollutant degradation and hydrogen generation was further evaluated with rare earth metal (lanthanum)- and nonmetal (nitrogen)-doped TiO₂, which also showed a positive response. Using a combination of ab initio calculations and our new theory model, we revealed that the enhanced photocatalytic performance of Ag/TiO₂ was due to the surface Fermi-level change of TiO₂ and lowered surface reaction energy barrier for water pollutant oxidation. This work opens new opportunities for exploiting tandem photocatalytic routes beyond water splitting and understanding the simultaneous reactions in metal-doped metal oxide photocatalyst systems under natural sunlight.

Non-Noble Plasmonic Metal-Based Photocatalysts

Solar-to-chemical energy conversion via heterogeneous photocatalysis is one of the sustainable approaches to tackle the growing environmental and energy challenges. Among various promising photocatalytic materials, plasmonic-driven photocatalysts feature prominent solar-driven surface plasmon resonance (SPR). Non-noble plasmonic metals (NNPMs)-based photocatalysts have been identified as a unique alternative to noble metal-based ones due to their advantages like earth-abundance, cost-effectiveness, and large-scale application capability. This review comprehensively summarizes the most recent advances in the synthesis, characterization, and properties of NNPMs-based photocatalysts. After introducing the fundamental principles of SPR, the attributes and functionalities of NNPMs in governing surface/interfacial photocatalytic processes are presented. Next, the utilization of NNPMs-based photocatalytic materials for the removal of pollutants, water splitting, CO₂ reduction, and organic transformations is discussed. The review concludes with current challenges and perspectives in advancing the NNPMs-based photocatalysts, which are timely and important to plasmon-based photocatalysis, a truly interdisciplinary field across materials science, chemistry, and physics.

Recent advances in Co-based co-catalysts for efficient photocatalytic hydrogen generation

Recent progress in photocatalytic hydrogen generation reaction highlights the critical role of co-catalysts in enhancing the solar-to-fuel conversion efficiency of diverse band-matched semiconductors. Because of the compositional flexibility, adjustable microstructure, tunable crystal phase and facet, cobalt-based co-catalysts have stimulated tremendous attention as they have high potential to promote hydrogen evolution reaction. However, a comprehensive review that specifically focuses on these promising materials has not been reported so far. Therefore, this present review emphasizes the recent progress in the pursuing of highly efficient Co-based co-catalysts for water splitting, and the advances in such materials are summarized through the analysis of structure-activity relationships. The fundamental principles of photocatalytic hydrogen production are profoundly outlined, followed by an elaborate discussion on the crucial parameters influencingthe reaction kinetics. Then, the co-catalytic reactivities of various Co-based materials involving Co, Co oxides, Co hydroxides, Co sulfides, Co phosphides and Co molecular complexes, etc, are thoroughly discussed when they are coupled with host semiconductors, with an insight towards the ultimateobjective of achieving a rationally designed photocatalyst for enhancing water splitting reaction dynamics. Finally, the current challenge and future perspective of Co-based co-catalysts as the promising noble-metal alternative materials for solar hydrogen generation are proposed and discussed.

Phytogenic Synthesis of Pd-Ag/rGO Nanostructures Using Stevia Leaf Extract for Photocatalytic H2 Production and Antibacterial Studies

Continuously increasing energy demand and growing concern about energy resources has attracted much research in the field of clean and sustainable energy sources. In this context, zero-emission fuels are required for energy production to reduce the usage of fossil fuel resources. Here, we present the synthesis of Pd-Ag-decorated reduced graphene oxide (rGO) nanostructures using a green chemical approach with stevia extract for hydrogen production and antibacterial studies under light irradiation. Moreover, bimetallic nanostructures are potentially lime lighted due to their synergetic effect in both scientific and technical aspects. Structural characteristics such as crystal structure and morphological features of the synthesized nanostructures were analyzed using X-ray diffraction and transmission electron microscopy. Analysis of elemental composition and oxidation states was carried out by X-ray photoelectron spectroscopy. Optical characteristics of the biosynthesized nanostructures were obtained by UV-Vis absorption spectroscopy, and Fourier transform infrared spectroscopy was used to investigate possible functional groups that act as reducing and capping agents. The antimicrobial activity of the biosynthesized Pd-Ag-decorated rGO nanostructures was excellent, inactivating 96% of Escherichia coli cells during experiments over 150 min under visible light irradiation. Hence, these biosynthesized Pd-Ag-decorated rGO nanostructures can be utilized for alternative nanomaterial-based drug development in the future.

Hollow Mesoporous Bi@PEG-FA Nanoshell as a Novel Dual-Stimuli-Responsive Nanocarrier for Synergistic Chemo-Photothermal Cancer Therapy

The development of stimuli-responsive multifunctional nanocarriers for therapeutic drug delivery is extremely desirable for highly specific treatment of disease. Herein, thiol-polyethylene glycol-folate acid-modified hollow mesoporous bismuth nanoshells (HM-Bi@PEG-FA NSs) were developed as the new dual-stimuli-responsive single-"elemental" photothermal nanocarriers for synergistic chemo-photothermal therapy of tumor. The designed hollow-mesoporous-type nanocarriers present excellent photothermal conversion capacity (∼34.72%) and good biocompatibility. Meanwhile, acidic pH and near-infrared (NIR) laser dual-stimulated doxorubicin (DOX) release is successfully achieved. More importantly, the DOX-loaded HM-Bi@PEG-FA NSs hold an efficient in vitro/in vivo antitumor effect through the synergistic chemo-photothermal therapy. Therefore, our findings provide the possibility of designing a dual-stimuli-responsive hollow mesoporous Bi-based photothermal nanocarrier for synergistically enhanced antitumor therapy.

Ultra-small intermetallic NiZn nanoparticles: a non-precious metal catalyst for efficient electrocatalysis

Intermetallics are long-range-ordered alloys traditionally synthesized by annealing nanoparticles of a random alloy, which results in the sintering of the nanoparticles and leads to the formation of polydispersed samples. It thus remains a challenge to achieve a monodispersion of tiny intermetallics. In the current work, ultra-small monodisperse intermetallic NiZn nanoparticles were synthesized based on a low-temperature solution chemistry route involving the chemical conversion of metal nanoparticles into an ordered alloy using an organometallic zinc precursor. During the transformation of single metal nanoparticles into the corresponding alloy, the particles retained their morphology. The resulting ordered alloy made up of earth-abundant materials demonstrated high electrocatalytic performance for the oxygen evolution reaction (OER) with a low overpotential of 283 mV at a current density of 10 mA cm^-2 and a small Tafel slope of 73 mV dec^-1, along with excellent stability and durability. The prepared intermetallic NiZn exhibited outstanding OER efficacy, better than those of a Ni_0.7Zn_0.3 alloy, pure Ni nanoparticles and even state-of-the art RuO₂. The atomic ordering as well as the modification of the electronic structure of Ni upon becoming alloyed with Zn, together with an atomic-scale synergistic effect produced from Ni and Zn, led to the enhanced intrinsic catalytic activity. The present findings point to a general route to produce nanoscale tiny alloys and also provide excellent electrocatalysts having exceptional energy conversion efficiency.

Selective photocatalytic C–C coupling of isopropanol into pinacol with concurrent hydrogen evolution over GONaOH photocatalyst

The average H₂ evolution rate could reach 7.36 mmol h⁻¹ over GO_NaOH photocatalyst. And meanwhile, the sacrificial agent isopropanol could undergo highly selective C–C coupling into pinacol. The isopropanol conversion rate was 77.95%, and the pinacol selectivity was 62.32%.

From Complex Inorganic Oxides to Ag-Bi Nanoalloy: Synthesis by Femtosecond Laser Irradiation

Bimetallic nanoalloys with a wide variety of structures and compositions have been fabricated through many diverse techniques. Generally, various steps and chemicals are involved in their fabrication. In this study, the synthesis of Ag-Bi nanoalloys by femtosecond laser irradiation of an inorganic oxide Ag₂WO₄/NaBiO₃ target without any chemicals like reducing agents or solvent is presented. The interaction between these materials and the ultrashort pulse of light allows the migration of Ag and Bi atoms from the crystal lattice to the particles surfaces and then to the plasma plume, where the reduction of the positively charged Ag and Bi species in their respective metallic species takes place. Subsequently, the controlled nucleation and growth of the Ag-Bi alloyed nanoparticles occurs in situ during the irradiation process in air. Although at the bulk level, these elements are highly immiscible, it was experimentally demonstrated that at nanoscale, the Ag-Bi nanoalloy can assume a randomly mixed structure with up to 6 ± 1 atom % of Bi solubilized into the face-centered cubic structure of Ag. Furthermore, the Ag-Bi binary system possesses high antibacterial activity against Staphylococcus aureus (methicillin-resistant and methicilin-susceptible), which is interesting for potential antimicrobial applications, consequently increasing their range of applicability. The present results provide potential insights into the structures formed by the Ag-Bi systems at the nanoscale and reveal a new processing method where complex inorganic oxides can be used as precursors for the controlled synthesis of alloyed bimetallic nanoparticles.

MoS2 Nanosheet-Modified CuInS2 Photocatalyst for Visible-Light-Driven Hydrogen Production from Water

Exploiting photocatalysts respond to visible light is of huge challenge for photocatalytic H2 production. Here, we synthesize a new composite material consisting of few-layer MoS2 nanosheets grown on CuInS2 surface as an efficient photocatalyst for solar H2 generation. The photocatalytic results demonstrate that the 3 wt % MoS2 /CuInS2 photocatalyst exhibits the highest H2 generation rate of 316 μmol h(-1)  g(-1) under visible light irradiation, which is almost 28 times higher than that of CuInS2 . Importantly, the MoS2 /CuInS2 photocatalyst shows a much higher photocatalytic activity than that of Pt-loaded CuInS2 photocatalyst. The enhanced photocatalytic activities of MoS2 /CuInS2 photocatalysts can be attributed to the improved charge separation at the interface of MoS2 and CuInS2, which is demonstrated by the significant enhancement of photocurrent responses in MoS2 /CuInS2 photoelectrodes. This work presents a noble-metal-free photocatalyst that responds to visible light for solar H2 generation.

Recent advances in the synthesis and application of photocatalytic metal–metal oxide core–shell nanoparticles for environmental remediation and their recycling process

Metal–metal oxide core–shell nanoparticles have received enormous research attention owing to their fascinating physicochemical properties and extensive applications. In this review we have discussed the challenges and recent advances in their synthesis and application.

The role of Sn in enhancing the visible-light photocatalytic activity of hollow hierarchical microspheres of the Bi/BiOBr heterojunction

The synergistic effect of oxygen vacancies and the Bi/BiOBr heterojunction broadens the light absorption range and promotes the charge separation efficiency.

Photo-synergistic promoted in situ generation of Bi0–BiSbO4 nanostructures as an efficient catalyst for nitrobenzene reduction

This work reports on the construction of Bi⁰–BiSbO₄ nanostructures to show photo-synergistic and efficient catalytic activity toward nitrobenzenes reduction.