Cationic vacancy engineering of p-TiO2 for enhanced photocatalytic nitrogen fixation

Engineering Ordered-Disordered Domains for High-Performance Energy Storage in BCZT-Based Relaxor Ferroelectrics

Dielectric capacitors have attracted considerable interest for energy storage applications owing to their ultra-fast charge-discharge capabilities. However, the concurrent realization of high recoverable energy storage density (Wrec) and energy efficiency (η) remains a persistent challenge. In this study, NaNbO3 (NN) is introduced into the 0.85Ba0.85Ca0.15Zr0.1Ti0.9O3-0.15Bi(Zn2/3Ta1/3)O3 (BCZT-0.15BZT) lattice, resulting in the emergence of a unique structural feature identified as ordered-disordered domains (O-DO-Ds). Detailed analysis reveals that the ordered domains exhibit ferroelectric hysteresis behavior, consistent with previous reports, while the disordered domains play a critical role in enhancing both breakdown strength and energy storage efficiency. These improvements are primarily attributed to energy dissipation mechanisms and the stabilization of a triple-phase coexistence. Additionally, the formation of defect dipoles and the presence of weakly coupled orthorhombic-tetragonal-cubic (O-T-C) asymmetric phases contribute synergistically to achieving high polarization and low hysteresis. Consequently, the optimized composition, (1-x)BCZT-0.15BZT-xNN with x = 0.15 exhibits an exceptionally high Wrec of 9.12 J cm-3 and an η of 95.3%. These findings offer a promising and innovative strategy for the design of next-generation high-performance energy storage capacitors.

Boosting the energy storage performance of BCZT-based capacitors by constructing a Schottky contact

Multilayer thin films composed of dielectric Ba0.7Ca0.3Zr0.2Ti0.8O3 (BCZT) and oxygen-deficient BCZT (BCZT-OD) were fabricated on (001)-oriented NSTO substrates using the pulsed laser deposition (PLD) technique. Unlike conventional approaches to energy storage capacitors, which primarily focus on compositional or structural modifications, this study explored the influence of the layer sequence and periodicity. The interface between the NSTO substrate and the BCZT-OD layer forms a Schottky barrier, resulting in electric field redistribution across the sublayers of the BCZT/BCZT-OD//(1P) thin film. This redistribution delays the breakdown of the BCZT layer, significantly enhancing the film's electric breakdown strength. Furthermore, mathematical analysis reveals that the electric field redistribution amplifies dipole polarization, with BCZT-OD-initiated multilayers exhibiting superior polarization compared to those with equivalent periodicity but different starting layers. Consequently, the BCZT/BCZT-OD//(1P) multilayer achieves an exceptional recoverable energy density (Wrec) of 150.22 J cm-3 and an energy efficiency (η) of 83.07%, surpassing typical performance benchmarks for BCZT-based thin films. These findings are corroborated by comprehensive structural characterization studies, performance evaluations, and finite element simulations, which further validate the role of the Schottky barrier in enhancing voltage endurance. Analogous to "Tian Ji's Strategy for Horse Racing", this work achieved high Wrec by sacrificing the ferroelectricity of the negative side of the P-E loop, introducing an innovative paradigm for designing and developing next-generation electronic devices.

Dual-scale modified BiOBr with enhanced structural self-transformation at wide pH for bifunctional treatment of Cr(VI)

Hexavalent chromium (Cr(VI)) poses threat to both ecosystems and human health. Complex pollution conditions, particularly the pH levels, significantly influence the treatment process of Cr(VI). In this study, BiOBr materials were synthesized with exposed (110) facets and Bi vacancies through dual modifications at both grain and atomic scales. The modified material exhibits a unique pH-adaptive structural transformation capability, enhancing the treatment of Cr(VI) under variable pH conditions. This structural adaptability notably enhances the bifunctional utility of modified BiOBr under visible light. Specifically, under acidic conditions, the material's surface undergoes restructuring, progressively exposing the (001) facets in conjunction with the original (110) facets to form a heterojunction, thereby enhancing reduction capacity. Under neutral to alkaline conditions, visible-light induced surface defects increase the availability of CrO42- ion-exchange channels, enhancing intercalation adsorption capacity. Additionally, facet and vacancy modifications improve the separation of charge carriers and expose more intercalation channels, enhance the pH adaptability and bifunctionality of modified BiOBr. Ultimately, the system demonstrates superior Cr(VI) removal efficiencies exceeding 90 % from pH 2-10. This innovative bifunctional BiOBr not only redefines the reaction mechanism in the Cr(VI) treatment system but also lays the groundwork for designing pH-adaptive catalysts aimed at environmental remediation.

Single-Atom Mo Supported by TiO2 for Photocatalytic Nitrogen Fixation

The challenge of achieving efficient photocatalysts for the fixation of ambient nitrogen to ammonia persists. The utilization efficiency of single-metal-atom catalysts leads to an increased number of active sites, while their distinctive geometrical and electronic characteristics contribute to enhancing the intrinsic activity of each individual site. In this study, we present a method using an organic molecule to assist in loading TiO2 with Mo single atoms for the purpose of photocatalytic nitrogen fixation. By adjusting the number of Mo single atoms loaded, we were able to regulate the microenvironment surrounding the catalytic center. Our results demonstrate that TiO2-Mo10 achieved a remarkable photocatalytic nitrogen fixation performance of 42.05 μmol·g-1·h-1 at room temperature while maintaining excellent structural stability and cycle life. The incorporation of Mo single atoms effectively enhanced electron separation and migration within TiO2, leading to a significant weakening of the N≡N bond. This research highlights the potential for predesigning TiO2-based single-atom photocatalysts with tailored structures for efficient nitrogen fixation through photocatalysis. These findings offer valuable insights for the future development and rational design of single-atom photocatalysts.

Light-driven nitrogen fixation routes for green ammonia production

The global goal for decarbonization of the energy sector and the chemical industry could become a reality by a massive increase in renewable-based technologies. For this clean energy transition, the versatile green ammonia may play a key role in the future as a fossil-free fertilizer, long-term energy storage medium, chemical feedstock, and clean burning fuel for transportation and decentralized power generation. The high energy-intensive industrial ammonia production has triggered researchers to look for a step change in new synthetic approaches powered by renewable energies. This review provides a comprehensive comparison of light-mediated N2 fixation technologies for green ammonia production, including photocatalytic, photoelectrocatalytic, PV-electrocatalytic and photothermocatalytic routes. Since these approaches are still at laboratory scale, we examine the most recent developments and discuss the open challenges for future improvements. Last, we offer a technoeconomic comparison of current and emerging ammonia production technologies, highlighting costs, barriers, recommendations, and potential opportunities for the real development of the next generation of green ammonia solutions.

Pushing Theoretical Potassium Storage Limits of MXenes through Introducing New Carbon Active Sites

Surface-driven capacitive storage enhances rate performance and cyclability, thereby improving the efficacy of high-power electrode materials and fast-charging batteries. Conventional defect engineering, widely-employed capacitive storage optimization strategy, primarily focuses on the influence of defects themselves on capacitive behaviors. However, the role of local environment surrounding defects, which significantly affects surface properties, remains largely unexplored for lack of suitable material platform and has long been neglected. As proof-of-concept, typical Ti3C2Tx MXenes are chosen as model materials owing to metallic conductivity and tunable surface properties, satisfying the requirements for capacitive-type electrodes. Using density functional theory (DFT) calculations, the potential of MXenes with modulated local atomic environment is anticipated and introducing new carbon sites found near pores can activate electrochemically inert surface, attaining record theoretical potassium storage capacities of MXenes (291 mAh g-1). This supposition is realized through atomic tailoring via chemical scissor within sublayers, exposing new sp3-hybridized carbon active sites. The resulting MXenes demonstrate unprecedented rate performance and cycling stability. Notably, MXenes with higher carbon exposure exhibit a record-breaking capacity over 200 mAh g-1 and sustain a capacity retention higher than 80% after 20 months. These findings underscore the effectiveness of regulating defects' neighboring environment and illuminate future high-performance electrode design.

Structurally and surficially activated TiO2 nanomaterials for photochemical reactions

Renewable fuels and environmental remediation are of paramount importance in today's world due to escalating concerns about climate change, pollution, and the finite nature of fossil fuels. Transitioning to sustainable energy sources and addressing environmental pollution has become an urgent necessity. Photocatalysis, particularly harnessing solar energy to drive chemical reactions for environmental remediation and clean fuel production, holds significant promise among emerging technologies. As a benchmark semiconductor in photocatalysis, TiO2 photocatalyst offers an excellent solution for environmental remediation and serves as a key tool in energy conversion and chemical synthesis. Despite its status as the default photocatalyst, TiO2 suffers from drawbacks such as a high recombination rate of charge carriers, low electrical conductivity, and limited absorption in the visible light spectrum. This review provides an in-depth exploration of the fundamental principles of photocatalytic reactions and presents recent advancements in the development of TiO2 photocatalysts. It specifically focuses on strategic approaches aimed at enhancing the performance of TiO2 photocatalysts, including improving visible light absorption for efficient solar energy harvesting, enhancing charge separation and transportation efficiency, and ensuring stability for robust photocatalysis. Additionally, the review delves into the application of photodegradation and photocatalysis, particularly in critical processes such as water splitting, carbon dioxide reduction, nitrogen fixation, hydrogen peroxide generation, and alcohol oxidation. It also highlights the novel use of TiO2 in plastic polymerization and degradation, showcasing its potential for converting plastic waste into valuable chemicals and fuels, thereby offering sustainable waste management solutions. By addressing these essential areas, the review offers valuable insights into the potential of TiO2 photocatalysis for addressing pressing environmental and energy challenges. Furthermore, the review encompasses the application of TiO2 photochromic systems, expanding its scope to include other innovative research and applications. Finally, it addresses the underlying challenges and provides perspectives on the future development of TiO2 photocatalysts. Through addressing these issues and implementing innovative strategies, TiO2 photocatalysis can continue to evolve and play a pivotal role in sustainable energy and environmental applications.

A polarization double-enhancement strategy to achieve super low energy consumption with ultra-high energy storage capacity in BCZT-based relaxor ferroelectrics

Due to dielectric capacitors' already-obtained fast charge-discharge speed, research has been focused on improving their Wrec. Increasing the polarization and enhancing the voltage endurance are efficient ways to reach higher Wrec, however simultaneous modification still seems a paradox. For example, in the ferroelectric-to-relaxor ferroelectric (FE-to-RFE) phase transition strategy, which has been widely used in the latest decade, electric breakdown strength (Eb) and energy storage efficiency (η) always increase, while at the same time, the maximum polarization (Pmax) inevitably decreases. The solution to this problem can be obtained from another degree of freedom, like defect engineering. By incorporating Bi(Zn2/3Ta1/3)O3 (BZT) into the Ba0.15Ca0.85Zr0.1Ti0.9O3 (BCZT) lattice to form (1 - x)Ba0.15Ca0.85Zr0.1Ti0.9O3-xBi(Zn2/3Ta1/3)O3 (BCZT-xBZT) solid-solution ceramics, in this work, ultrahigh ferroelectric polarization was achieved in BCZT-0.15BZT, which is caused by the polarization double-enhancement, comprising the contribution of interfacial and dipole polarization. In addition, due to the electron compensation, a Schottky contact formed at the interface between the electrode and the ceramic, which in the meantime, enhanced its Eb. A Wrec of 8.03 J cm-3, which is the highest among the BCZT-based ceramics reported so far, with an extremely low energy consumption, was finally achieved. BCZT-0.15BZT also has relatively good polarization fatigue after long-term use, good energy storage frequency stability and thermal stability, as well as excellent discharge properties.

Enhanced Photocatalytic Nitrogen Reduction via Bismuth Nanoparticle-Decorating ZnCdS Solid Solution

The construction of photocatalysts with a surface plasmon resonance effect (SPR) has been demonstrated as a highly effective strategy for enhancing photocatalytic efficiency. In this paper, we synthesized a catalyst with bismuth metal loaded on ZnCdS nanospheres for an efficient photocatalytic nitrogen reduction reaction (PNRR). The SPR effect induced by Bi nanoparticles under light excitation significantly promoted the ammonia production efficiency of the photocatalyst. Under air ambient conditions with lactic acid as the sacrificial agent, the photocatalytic NH4+ yield of 3% Bi@ZnCdS was 58.93 μmol·g-1·h-1, which exhibited an approximately 7.7 times that of the pure phase ZnCdS. The experimental characterization results demonstrate that the incorporation of metallic bismuth enhances the light absorption capacity of the catalyst and improves the separation efficiency of the photogenerated carriers. Theoretical calculations proved that Bi NPs provide more photogenerated electrons to convert N2 to NH3 for solid-solution ZnCdS. This work presents a novel concept for the development of advanced plasma nanomaterials to enhance the photocatalytic nitrogen fixation reaction.

Photoelectrochemical-driven nitrogen reduction to ammonia by a Vo-SnO2/TiO2 composite electrode

N2 molecules with the NN triple bond structure are difficult to cleave under mild conditions to achieve the nitrogen fixation reaction. Photoelectrochemical (PEC) catalysis technology combining the advantages of photocatalysis and electrocatalysis provides the possibility of the nitrogen reduction reaction under ambient conditions. Herein, an SnO2/TiO2 photoelectrode was first fabricated through depositing SnO2 quantum dots on TiO2 nanorod arrays via a simple hydrothermal method. The oxygen vacancy (Vo) content was then induced in SnO2 through annealing SnO2/TiO2 at high temperature under an inert atmosphere. The heterogeneous structure of Vo-SnO2 quantum dots and TiO2 nanorods boosted the separation of photocarriers. The photoelectrons generated by photoexcitation were transferred from the conduction band of TiO2 to the conduction band of Vo-SnO2 and trapped by Vo. Vo activates N2 molecules adsorbed on the catalyst surface, and reacts with H+ in the electrolyte to generate NH3. The nitrogen fixation yield of PEC catalysis and its faradaic efficiency can reach 19.41 μg cm-2 h-1, and 59.6% at -0.2 V bias potential, respectively. The heterogeneous structure of Vo-SnO2/TiO2, introduction of Vo and synergistic effect between light and electricity greatly promotes the PEC nitrogen reduction to NH3.

Microchemical environmental regulation of POMs@MIL-101(Cr) promote photocatalytic nitrogen to ammonia

The polyoxometalates (POMs) have been shown to be highly effective as reactive sites for photocatalytic nitrogen fixation reactions. However, the effect of POMs regulation on catalytic performance has not been reported yet. Herein, a series of composites (SiW₉M₃@MIL-101(Cr) (M = Fe, Co, V, Mo) and D-SiW₉Mo₃@MIL-101(Cr), D, Disordered) were obtained by regulating transition metal compositions and arrangement in the POMs. The ammonia production rate of SiW₉Mo₃@MIL-101(Cr) is much higher than that of other composites, reaching 185.67 μmol·h^-1·g^-1_cat in N₂ without sacrificial agents. The structural characterization of composites reveals that the increase of the electron cloud density of W atom in composites is the key to improve the photocatalytic performance. In this paper, the microchemical environment of POMs was regulated by transition metal doping method, thereby promoting the efficiency of photocatalytic ammonia synthesis for the composites, which provides new insights into the design of POM-based photocatalysts with high catalytic activity.