Applied Catalysis B: Environmental最新文献

Turning the harmful NO into value-added chemicals is a promising alternative to achieve the electrocatalytic NO upgrading and maintain the global N-balance. However, the reaction mechanisms and electrochemical performances and are still needed to be further investigated. Herein, the development of electrochemical NO reduction and oxidation reaction (NORR and NOOR) were respectively summarized. In the NORR part, we summarized the electrocatalytic reaction systems, including directly NORR (NO to NH₃/NH₂OH) and the C-N coupling reactions with CO_x for urea, and organic molecules for amino acid, oxime. The reaction mechanisms and design principles of electrocatalysts for different reaction systems were reviewed, combining theoretical calculations and advanced characterization techniques. The NO reaction is also a potential approach to replace others cathodic reduction. Finally, the challenges and outlooks in this fields have been proposed. The electrocatalytic NO reaction not only realizes the efficient green utilization, but also provides guidance for nitrogen economy.

Here, we demonstrate the selective cellobiose (building block of cellulose) photoreforming for gluconic acid and syngas co-production in acidic conditions by rationally designing a bifunctional polymeric carbon nitride (CN) with potassium/sulfur co-dopant. This heteroatomic doped CN photocatalyst possesses enhanced visible light absorption, higher charge separation efficiency than pristine CN. Under acidic conditions, cellobiose is not only more efficiently hydrolyzed into glucose but also promotes the syngas and gluconic acid production. Density functional theory (DFT) calculations reveal the favorable generation of •O₂⁻ during the photocatalytic reaction, which is essential for gluconic acid production. Consequently, the fine-designed photocatalyst presents excellent cellobiose conversion (>80%) and gluconic acid selectivity (>70%) together with the co-production of syngas (∼56 μmol g⁻¹ h⁻¹) under light illumination. The current work demonstrates the feasibility of biomass photoreforming with value-added chemicals and syngas co-production under mild condition.

Developing corrosion-resistant oxygen evolution electrocatalysts that can sustain seawater electrolysis is crucial but challenging for hydrogen production. Herein, we develop a bimetallic oxyhydroxide electrocatalyst with self-derived selenate space charge layer (SeO₄²⁻ SCL) by in-situ electrochemically reconstructing cobalt-doped nickel diselenide (Co-NiSe₂) pre-catalyst, enabling long-term stability for seawater electrolysis. In-situ experiments and theoretical results reveal the promoting effect of cobalt-doping on the reconstruction of NiSe₂ and generation of dynamically stable oxygen vacancy sites. Importantly, the SeO₄²⁻ SCL derived from the reconstruction process shows a dynamic anti-corrosion behavior, thus protecting metal species from dissolution and meanwhile without blocking the diffusion and adsorption of reactive species. Consequently, a two-electrode cell assembled by this Co-NiSe₂ pre-catalyst as an anode, reaches an industrial current density (500 mA cm⁻²) at a cell voltage of 1.70 V, and that works stably for over 1500 h in alkaline seawater, which is of significance for promoting the practicality of low-cost catalysts.

A mechanochemical synthesis method has been used to synthesize CoRu nanoparticles supported on CeO₂ for methane dry reforming. In this work, we study the effect of Ru addition to Co/CeO₂-based catalysts and of the synthesis method by screening their catalytic activity, using synchrotron X-ray diffraction (XRD), and operando near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). Ruthenium addition directly impacts the reducibility of cobalt species and results in smaller particle sizes, as demonstrated by H₂-temperature programmed reduction and XRD. NAP-XPS shows that Ru modifies the metal-support interaction, as evidenced by the higher Ce³⁺/Ce ratios for the bimetallic samples and tuning the oxidation state of Ru. The synthesis method also influences the dispersion of Co and Ru on the surface. Mechanochemically-prepared samples (mono- and bimetallic) outperformed the conventionally-synthesized counterparts by reaching higher CH₄ and CO₂ conversions, resulting in a stable CoRu/CeO₂ catalyst for 24 h at 700 °C and yielding an H₂/CO ratio close to 1.

Coupling hydrazine electrooxidation with hydrogen evolution reaction (HER) attracts ever-growing attention for energy-saving H₂ production. However, the performance of hydrazine-assisted HER unit is restricted by the bifunctional catalysts with un-fully activated sites. Herein, a surface local-reconstruction strategy is proposed to integrate amorphous Co(OH)₂ and P vacant CoP into the CoH-CoP_V@CFP catalyst. The inherent electron-deficient Co sites in Co(OH)₂ show strong N-Co interaction to accelerate the N₂H₄ dehydrogenation kinetics, while the as-formed P vacancies in CoP play a crucial role in moderating the H* adsorption energy, the excellent bifunctionality thus being obtained. Specifically, it achieves the low overpotentials of − 77 and − 61 mV at 10 mA cm⁻² for HER and HzOR in alkaline media, respectively. A lab-scale electrolyzer can deliver the industrial-grade current density of 500 mA cm⁻² under ultralow cell voltage of 0.23 V. This local-reconstruction strategy may pave new avenue to design efficient catalysts for hydrazine-assisted H₂ generation.

Developing highly active and robust transition metal chalcogenides (TMCs) electrocatalysts toward oxygen evolution reaction (OER) remains a challenge. Herein, we report an electron redistribution mechanism that involves the metal-sulfur (M-S) bond stabilization triggered by electron transfer from Ce to Ni and Co in CeO₂/NiCo₂S₄ heterostructure, thereby effectively inhibiting the leaching of sulfur from CeO₂/NiCo₂S₄ during the OER process. Moreover, the well-modulated heterogeneous interface enables optimal adsorption affinity for oxygen intermediates and reduces the energy barrier of OER. As a result, CeO₂/NiCo₂S₄ exhibits superior OER activity with ultralow overpotentials of 146 and 271 mV at 10 and 100 mA cm⁻², respectively. More importantly, CeO₂/NiCo₂S₄ possesses excellent durability for over 200 h at 500 mA cm⁻², surpassing individual NiCo₂S₄ and most of the reported TMCs-based electrocatalysts. This work provides new insights for achieving good compatibility of TMCs-based OER electrocatalysts in terms of high activity and stability.

The Ag nanoparticles (Ag_NPs) in Ag/Al₂O₃ catalysts play a crucial role in the selective catalytic oxidation of NH₃ (NH₃-SCO). To enhance NH₃-SCO activity, Cu, which has stronger anchoring ability than Ag, is introduced onto Al₂O₃, reducing available anchoring sites for Ag. As Ag cannot displace anchored Cu species, Ag species agglomerate into larger Ag_NPs even with low Ag loading. Consequently, these enlarged Ag_NPs become more active centers for NH₃-SCO. The optimal Ag:Cu molar ratio is confirmed as 2:3. This 'pre-occupied-anchoring-site’ strategy decreases Ag loading to 1/5 of the original, reducing catalyst costs while maintaining activity. In situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) studies reveal that NH₃-SCO on 2Ag1.8Cu/Al (weight ratio) catalyst follows the hydrazine mechanism below 200 °C, coexisting with the imide mechanism from 200–250 °C, and solely the imide mechanism beyond 250 °C. This strategy is applicable to various transition metals, including Mn, Co, Ni, and Fe, promoting cost-effective Ag_NPs formation.

Preparation of porous micro-sized materials with solar response is urgent for fast commercialization of green technologies based on semiconductor photocatalysis. Here, mesoporous titania microballs composed of nanocrystalline anatase with exposed facets were prepared by a sub-zero sol-gel method followed by hydrothermal/alcohothermal crystallization. The mechanism of microballs formation and the influence of preparation conditions on the properties, and thus resultant photocatalytic activity, were investigated in detail. The photocatalytic performance was examined in four reaction systems under UV/vis irradiation, i.e., oxidative decomposition of methyl orange (MO) dye, hydrogen evolution, degradation of tetracycline (TC) antibiotic, and carbon dioxide reduction. Moreover, hydrogen generation was also examined under visible-light (vis) irradiation. Amorphous and faceted (octahedral- and decahedral-based) microballs were additionally modified with nanoparticles (NPs) of noble metals (Pt, Au, Ag, Pt/Au, Pt/Ag) for both UV-activity enhancement and vis response (i.e., plasmonic photocatalysis). It has been found that nano-architecture of microballs might be controlled by the ratio of alcohol to water used during hydrothermal/alcohothermal treatment. Accordingly, highly active microballs composed of pure octahedral- or decahedral-shaped anatase crystals, i.e., with {101} facets only (bipyramids) or eight {101} and two {001} facets, respectively, could be synthesized by a facile and environmental-friendly method. The versatility and high activity of faceted microballs have been confirmed in both oxidation and reduction reactions under UV and/or vis irradiation (comparable performance to that by famous P25). Decahedral-based samples exhibit usually higher photocatalytic activity than octahedral ones, despite worse photoelectronic properties (charge carriers’ separation, electron transport capacity and photocurrent density), due to higher hydrophilicity. However, single type {101} facet photocatalyst (octahedral shape) is preferable for efficient CO₂ adsorption and reduction into CO and CH₄. Among noble metals, though platinum shows much higher positive effect on UV activity, gold is responsible for the highest activity under vis, which corresponds to the strongest plasmonic filed enhancement, as proven by finite difference time domain (FDTD) simulations. Concluding, micro-sized balls composed of faceted anatase are undoubtedly prospective photocatalyst for diverse environmental applications.

The catalytic oxidation of different volatile organic compounds (VOCs) has been widely studied for several decades within the field of air depollution. However, there is still much to understand regarding the effects that these VOCs have on each other when they are blended together in the reaction mixture, as would be expected in many emissions. Herein, the catalytic oxidation of toluene and 2-propanol on supported manganese oxides under both single and binary VOCs oxidation conditions has been studied. We have found the catalyst activity for VOCs mineralization and its selectivity towards other by-products (i.e., acetone or propylene from 2-propanol) to be strongly dependent on the reaction conditions, the catalyst redox properties and support acidity. We have also assessed the promotion/inhibition effects derived from the VOCs mixture and proposed the reaction mechanism in each case by means of in-situ DRIFTS measurements.

Metal ion doping is an extensively researched method to enhance photocatalytic activity of bismuth-based semiconductors, but function of the metal ions need be further clarified. Herein, metal-alcohol coordination was evidenced to promote reduction of Bi^III in Bi-based semiconductors (e.g., Bi₂MoO₆ hierarchical microspheres) to generated oxygen vacancies (Ovs) and Bi metal (Bi⁰). Ovs and Bi⁰, rather than widely recognized doping metal ions, play a key role for remarkable enhancement of photocatalytic activity of Bi₂MoO₆, for example of ∼16-fold higher photocatalytic nitrogen reduction activity, which arises from that the Ovs and Bi⁰ can enhance photoexcited charge separation and work as surface active sites. The Ovs possess much greater efficacy than the Bi⁰. Formation of Bi⁰ also induces prominent morphological variation of the microspheres. This work discloses an interesting but neglected phenomenon in alcohothermal synthesis of “metal-doped” Bi-based semiconductors and aims at drawing high attention of relevant researchers.