Perovskite Oxide LaNiO3Nanoparticles for Boosting H2Evolution over Commercial CdS with Visible Light

Progress on enhancing the charge separation efficiency of carbon nitride for robust photocatalytic H2 production

Solar-driven H2 production from water splitting with efficient photocatalysts is a sustainable strategy to meet the clean energy demand and alleviate the approaching environmental issues caused by fossil fuel consumption. Among various semiconductor-based photocatalysts, graphitic carbon nitride (g-C3N4) has attracted much attention due to its advantages of long term-stability, visible light response, low cost, and easy preparation. However, the intrinsic Coulombic attraction between charge carriers and the interlayer electrostatic barrier of bulk g-C3N4 result in severe charge recombination and low charge separation efficiency. This perspective summarizes the recent progress in the development of g-C3N4 photocatalytic systems, and focuses on three main modification strategies for promoting charge transfer and minimizing charge recombination, including structural modulation, heterojunction construction, and cocatalyst loading. Based on this progress, we provide conclusions regarding the current challenges of further improving photocatalytic efficiency to fulfill commercial requirements, and propose some recommendations for the design of novel and satisfactory g-C3N4 photocatalysts, which is expected to progress the solar-to-hydrogen conversion.

Noble Metals Deposited LaMnO3 Nanocomposites for Photocatalytic H2 Production

Due to the growing demand for hydrogen, the photocatalytic hydrogen production from alcohols present an intriguing prospect as a potential source of low-cost renewable energy. The noble metals (Ag, Au, Pd and Pt) deposited LaMnO₃ nanocomposites were synthesized by a non-conventional green bio-reduction method using aqueous lemon peel extract, which acts as both reducing and capping agent. The successful deposition of the noble metals on the surface of LaMnO₃ was verified by using powder XRD, FTIR, TEM, N₂-physisorption, DR UV-vis spectroscopy, and XPS techniques. The photocatalytic activity of the synthesized nanocomposites was tested for photocatalytic H₂ production under visible light irradiation. Different photocatalytic reaction parameters such as reaction time, pH, catalyst mass and reaction temperature were investigated to optimize the reaction conditions for synthesized nanocomposites. Among the synthesized noble metal deposited LaMnO₃ nanocomposites, the Pt-LaMnO₃ nanocomposite offered superior activity for H₂ production. The enhanced photocatalytic activity of the Pt-LaMnO₃ was found as a result from low bandgap energy, high photoelectrons generation and enhanced charge separation due to deposition of Pt nanoparticles. The effective noble metal deposition delivers a new route for the development of plasmonic noble metal-LaMnO₃ nanocomposites for photocatalytic reforming of aqueous methanol to hydrogen.

Molybdenum disulfide loading on a Z-scheme graphitic carbon nitride and lanthanum nickelate heterojunction for enhanced photocatalysis: Interfacial charge transfer and mechanistic insights

Interfacial design and the co-catalyst effect are considered to be effective to achieve separation and transport of photogenerated carriers in composite photocatalysts. In this study, a Z-scheme heterojunction was successfully combined with a co-catalyst to achieve a highly efficient LaNiO₃/g-C₃N₄/MoS₂ photocatalyst. MoS₂ flakes were loaded on a hybrid material surface, which was formed by LaNiO₃ nanocubes embedded on layered g-C₃N₄, and a good heterostructure with multiple attachment sites was obtained. Experimental studies confirmed that the Z-scheme heterojunction completely preserves the strong redox ability of the photogenerated electrons and holes. As a cocatalyst, MoS₂ further promoted interfacial charge separation and transport. The synergistic effect of the Z-scheme heterojunction and co-catalyst effectively realized the transfer of photogenerated carriers from "slow transfer" to "high transfer" and promoted water decomposition and pollutant degradation. Results revealed that under simulated sunlight irradiation, LaNiO₃/g-C₃N₄/MoS₂ composites exhibit superior hydrogen evolution of 45.1 μmol h^-1, which is 19.1 times that of g-C₃N₄ and 4.9 times that of LaNiO₃/g-C₃N₄, respectively. Moreover, the LaNiO₃/g-C₃N₄/MoS₂ Z-scheme photocatalyst exhibited excellent photocatalytic performance for antibiotic degradation and heavy-metal ion reduction under visible light. This study might provide some insights into the development of photocatalysts for solar energy conversion and environmental remediation.

Z-scheme LaCoO3/C3N5 for efficient full-spectrum light-simulated solar photocatalytic hydrogen generation

An inexpensive and efficient LaCoO3/C3N5 photocatalytic system for water splitting or other photocatalytic applications was designed. The photocatalytic reaction and mechanism of C3N5 and its complexes was verified.

Developing sustainable, high-performance perovskites in photocatalysis: design strategies and applications

Solar energy is attractive because it is free, renewable, abundant and sustainable. Photocatalysis is one of the feasible routes to utilize solar energy for the degradation of pollutants and the production of fuel. Perovskites and their derivatives have received substantial attention in both photocatalytic wastewater treatment and energy production because of their highly tailorable structural and physicochemical properties. This review illustrates the basic principles of photocatalytic reactions and the application of these principles to the design of robust and sustainable perovskite photocatalysts. It details the structures of the perovskites and the physics and chemistry behind photocatalytic reactions and describes the advantages and limitations of popular strategies for the design of photoactive perovskites. This is followed by examples of how these strategies are applied to enhance the photocatalytic efficiency of oxide, halide and oxyhalide perovskites, with a focus on materials with potential for practical application, that is, not containing scarce or toxic elements. It is expected that this overview of the development of photocatalysts and deeper understanding of photocatalytic principles will accelerate the exploitation of efficient perovskite photocatalysts and bring about effective solutions to the energy and environmental crisis.

Synergistic effect between La–Ni bimetallic oxides for the efficient decomposition of hydrogen peroxide

La–Ni bimetallic oxides with pure composition and well-crystalline structures were prepared, which showed high catalytic activities toward H₂O₂ decomposition.

Promoting photocatalytic hydrogen evolution over the perovskite oxide Pr0.5(Ba0.5Sr0.5)0.5Co0.8Fe0.2O3 by plasmon-induced hot electron injection

Exploration of highly efficient and stable photocatalysts for water splitting has attracted much attention. However, developing a facile and effective approach to enhance the photocatalytic activity for practical applications is still highly challenging. Herein, we report a newly-fabricated perovskite oxide (Pr_0.5(Ba_0.5Sr_0.5)_0.5Co_0.8Fe_0.2O₃) decorated with Au ultrafine nanoparticles for photocatalytic water splitting. An exceptionally high hydrogen evolution rate of 1618 μmol g^-1 h^-1 was achieved (under 2 h illumination) when the Au mass loading was optimized to 9.3 wt%, which is 540 times higher than that of the pristine one. The splendid photocatalytic activity of the sample was attributed to plasmon-excited hot electron injection from Au to Pr_0.5(Ba_0.5Sr_0.5)_0.5Co_0.8Fe_0.2O₃ (PBSCF) under illumination. The finite-difference time-domain simulations (FDTD) demonstrated that the localized strong electric field formed at the interface between Au and PBSCF under illumination, enables the hot electrons to be energetic and make the injection possible.

Synthesis of Novel Ternary Dual Z-scheme AgBr/LaNiO3/g-C3N4 Composite with Boosted Visible-Light Photodegradation of Norfloxacin

Promoting the separation of photogenerated charges and enhanced optical absorption capacity is the main means to modify photocatalytic capacities to advance semiconductor photocatalyst applications. For the first time, a novel ternary photocatalyst for dual Z-scheme system AgBr/LaNiO₃/g-C₃N₄ (ALG) was prepared via a modest ultrasound-assisted hydrothermal method. The results indicated that LaNiO₃ nanoballs and AgBr nanoparticles were successfully grown on the surface of g-C₃N₄ nanosheets. A dual Z-scheme photocatalytic reaction system could be constructed based on the energy band matching within AgBr, LaNiO₃ and g-C₃N₄. Metallic Ag during the photocatalytic reaction process acted as the active electrons transfer center to enhance the photocatalytic charge pairs separation. The chemical composition of ALG was optimized and composites with 3% AgBr, 30% LaNiO₃ and 100% g-C₃N₄ which was noted as 3-ALG displayed the best photocatalytic performance. A total of 92% of norfloxacin (NOR) was photodegraded within two hours over ALG and the photodegradation rate remained >90% after six cycles. The main active species during the degradation course were photogenerated holes, superoxide radical anion and hydroxyl radical. A possible mechanism was proposed based on the synergetic effects within AgBr, LaNiO₃ and g-C₃N₄. This work would offer a credible theoretical basis for the application of dual Z-scheme photocatalysts in environment restoration.

Rare-earth-containing perovskite nanomaterials: design, synthesis, properties and applications

As star material, perovskites have been widely used in the fields of optics, photovoltaics, electronics, magnetics, catalysis, sensing, etc. However, some inherent shortcomings, such as low efficiency (power conversion efficiency, external quantum efficiency, etc.) and poor stability (against water, oxygen, ultraviolet light, etc.), limit their practical applications. Downsizing the materials into nanostructures and incorporating rare earth (RE) ions are effective means to improve their properties and broaden their applications. This review will systematically summarize the key points in the design, synthesis, property improvements and application expansion of RE-containing (including both RE-based and RE-doped) halide and oxide perovskite nanomaterials (PNMs). The critical factors of incorporating RE elements into different perovskite structures and the rational design of functional materials will be discussed in detail. The advantages and disadvantages of different synthesis methods for PNMs will be reviewed. This paper will also summarize some practical experiences in selecting suitable RE elements and designing multi-functional materials according to the mechanisms and principles of REs promoting the properties of perovskites. At the end of this review, we will provide an outlook on the opportunities and challenges of RE-containing PNMs in various fields.

Highly selective conversion of CO2 to C2H6 on graphene modified chlorophyll Cu through multi-electron process for artificial photosynthesis

Artificial photosynthesis is a promising strategy for converting carbon dioxide into hydrocarbon fuels through solar energy as it is clean, economical and environmentally friendly. Herein, we developed a selective and stable photocatalyst for CO₂ photocatalytic reduction into C₂H₆ through a multi-electron transfer pathway without the external sacrificial regents. The core component of this composite catalyst was extracted from a silkworm excrement and modified to make chlorophyll Cu (Chl-Cu), which contained a porphyrin structure as an antenna for light absorption and a Cu cation as an active centre. We found that C₂ hydrocarbons such as C₂H₂, C₂H₄, and C₂H₆ tended to generate on chlorophyll-a/graphene. After substituting Mg²⁺ with Cu²⁺ cations in the centre of the porphyrin and modifying with graphene, only C₂H₆ was detected in the 18 hours reaction. This photocatalyst presented an outstanding activity and selectivity for the photocatalytic CO₂ reduction (CO₂RR) with a C₂H₆ yield rate at 68.23 μmol m^-2 h^-1 under visible light irradiation and an apparent quantum efficiency of 1.26% at 420 nm. In this system, the porphyrin rings were excited to produce electron-hole pairs by light. The photo-induced holes oxidized water to produce oxygen while graphene worked as an adsorption centre and electron acceptor for the CO₂ reduction.

Multifunctional All-Inorganic Flexible Capacitor for Energy Storage and Electrocaloric Refrigeration over a Broad Temperature Range Based on PLZT 9/65/35 Thick Films

Multifunctional capacitors can efficiently integrate multiple functionalities into a single material to further down-scale state-of-the-art integrated circuits, which are urgently needed in new electronic devices. Here, an all-inorganic flexible capacitor based on Pb_0.91La_0.09 (Zr_0.65Ti_0.35)_0.9775O₃ (PLZT 9/65/35) relaxor ferroelectric thick film (1 μm) was successfully fabricated on LaNiO₃/F-Mica substrate for application in electrostatic energy storage and electrocaloric refrigeration simultaneously. The flexible PLZT 9/65/35 thick film presents a desirable breakdown field of 1998 kV/cm, accompanied by a superior recoverable energy density (W_rec) of 40.2 J/cm³. Meanwhile, the thick film exhibits excellent stability of energy-storage performance, including a broad operating temperature (30-180 °C), reduplicative charge-discharge cycles (1 × 10⁷ cycles), and mechanical bending cycles (2000 times). Moreover, a large reversible adiabatic temperature change (ΔT) of 18.0 °C, accompanied by an excellent electrocaloric strength (ΔT/ΔE) of 22.4 K cm/V and refrigerant capacity (RC) of 11.2 J/cm³, is obtained at 80 °C in the flexible PLZT 9/65/35 thick film under the moderate applied electric field of 850 kV/cm. All of these results shed light on a flexible PLZT 9/65/35 thick film capacitor that opens up a route to practical applications in microenergy-storage systems and on-chip thermal refrigeration of advanced electronics.

Modulation of Polymeric Carbon Nitrides through Supramolecular Preorganization for Efficient Photocatalytic Hydrogen Generation

Supramolecular pre-assembly by design is an effective strategy to adapt the physicochemical properties of polymeric carbon nitrides (PCNs) to improve their solar conversion performance. A new supramolecular preorganization protocol, which employs H₂ O as the self-assembly medium and sodium persulfate as a modifier, is proposed to modulate the textural and photoelectronic features of PCNs for efficient visible-light H₂ evolution. Sodium persulfate is revealed to precisely tailor the final carbon nitride polymers with unusual porous layered structures and promoted charge separation and migration kinetics. As a result, the modulated PCNs with optimized structures show a greatly enriched activity for photocatalytic H₂ generation compared to the analogous materials derived from melamine without the modifier.

Deciphering Z-scheme Charge Transfer Dynamics in Heterostructure NiFe-LDH/N-rGO/g-C3N4 Nanocomposite for Photocatalytic Pollutant Removal and Water Splitting Reactions

A series of heterostructure NiFe LDH/N-rGO/g-C3N4 nanocomposite were fabricated by combining calcinations-electrostatic self-assembly and hydrothermal steps. In this method, negatively charged N-rGO was electrostaticaly bonded to the self-assembled interface of n-n type g-C3N4/NiFe LDH hybrid. XRD and AFM results revealed successful formation of heterostructure nanocomposite due to the coupling effect of exfoliated NiFe LDH nanosheets with N-rGO and g-C3N4. Among the as synthesized heterostructure, CNNG3LDH performed superior photocatalytic activities towards 95 and 72% mineralization of RhB and phenol. Furthermore, CNNG3LDH could achieve the highest photocatalytic H2 evolution rate of 2508 μmolg-12h-1 and O2 evolution rate of 1280 μmolg-12h-1 under visible light irradiation. The CNNG3LDH possess lowest PL intensity, reduced arc of the Nyquist plot (43.8 Ώ) and highest photocurrent density (-0.97 mA cm-2) which revealed effective charge separation for superior photocatalytic activities. TRPL spectral results reveal the synergistic effect of layered component in CNNG3LDH for achievable higher life time of excitons of ~16.52 ns. In addition, N-rGO mediator based Z-scheme charge transfer mechanisms in CNNG3LDH were verified by the ESR and TA-PL studies. Enriched oxygen vacancy type defects in NiFe LDH and N-rGO mediated Z-scheme charge transfer mechanistic path strongly manifest the superior photocatalytic activities of the heterostructure materials.