Hierarchical Ni−Al hydrotalcite supported Pt catalyst for efficient catalytic oxidation of formaldehyde at room temperature

Novel synergistically effects of palladium-iron bimetal and manganese carbonate carrier for catalytic oxidation of formaldehyde at room temperature

The elimination of formaldehyde at room temperature holds immense potential for various applications, and the incorporation of a catalyst rich in surface hydroxyl groups and oxygen significantly enhances its catalytic activity towards formaldehyde oxidation. By employing a coprecipitation method, we successfully achieved a palladium domain confined within the manganese carbonate lattice and doped with iron. This synergistic effect between highly dispersed palladium and iron greatly amplifies the concentration of surface hydroxyl groups and oxygen on the catalyst, thereby enabling complete oxidation of formaldehyde at ambient conditions. The proposed method facilitates the formation of domain-limited palladium within the MnCO3 lattice, thereby enhancing the dispersion of palladium and facilitating its partial incorporation into the MnCO3 lattice. Consequently, this approach promotes increased exposure of active sites and enhances the catalyst's capacity for oxygen activation. The co-doping of iron effectively splits the doping sites of palladium to further enhance its dispersion, while simultaneously modifying the electronic modification of the catalyst to alter formaldehyde's adsorption strength on it. Manganese carbonate exhibits superior adsorption capability for activated surface hydroxyl groups due to the presence of carbonate. In situ infrared testing revealed that dioxymethylene and formate are primary products resulting from catalytic oxidation of formaldehyde, with catalyst surface oxygen and hydroxyl groups playing a crucial role in intermediate product decomposition and oxidation. This study provides novel insights for designing palladium-based catalysts.

Alloying-Triggered Phase Engineering of NiFe System via Laser-Assisted Al Incorporation for Full Water Splitting

It is challenging to design one non-noble material with balanced bifunctional performance for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for commercial sustainability at a low cost since the different electrocatalytic mechanisms are not easily matchable for each other. Herein, a self-standing hybrid system Ni₁₈ Fe₁₂ Al₇₀ , consisting of Ni₂ Al₃ and Ni₃ Fe phases, was constructed by laser-assisted aluminum (Al) incorporation towards full water splitting. It was found that the incorporation of Al could effectively tune the morphologies, compositions and phases. The results indicate that Ni₁₈ Fe₁₂ Al₇₀ delivers an extremely low overpotential to trigger both HER (η₁₀₀ =188 mV) and OER (η₁₀₀ =345 mV) processes and maintains a stable overpotential for 100 h, comparable to state-of-the-art electrocatalysts. The synergistic effect of Ni₂ Al₃ and Ni₃ Fe alloys on the HER process is confirmed based on theoretical calculation.

Catalytic performance and mechanism of bismuth molybdate nanosheets decorated with platinum nanoparticles for formaldehyde decomposition at room temperature

Catalytic oxidation at room temperature is considered as a promising strategy for removal of formaldehyde (HCHO), a widely occurring indoor air pollutant. A series of Bi₂MoO₆ nanosheets were prepared via one-step hydrothermal synthesis in this study, followed by decoration with Pt nanoparticles (NPs). The catalyst with Bi₂MoO₆ support prepared at 180 °C exhibited high and stable activity in catalytic oxidation of HCHO at room temperature. The excellent catalytic performance was attributed to its large specific area and pore volume, high level of surface active oxygen species, high content of metallic Pt NPs, and abundant oxygen vacancies. The good synergy and interaction between Pt and Bi₂MoO₆ promoted electron transfer, and facilitated the adsorption and oxidation of HCHO. The electronic interaction between Pt NPs and Bi₂MoO₆ accelerated the activation of oxygen species due to weakening of the surface BiO or MoO bonds adjacent to Pt NPs. Infrared spectra indicated that dioxymethylene and formate species were the main intermediates of HCHO oxidation. Density functional theory calculations showed that the dehydrogenation of HCO₂, with an energy barrier of 282.1 kJ/mol, was the rate-determining step in catalytic oxidation process. This study provides new insights on the construction of high-efficiency catalysts for indoor formaldehyde removal.

Review on Catalytic Oxidation of VOCs at Ambient Temperature

As an important air pollutant, volatile organic compounds (VOCs) pose a serious threat to the ecological environment and human health. To achieve energy saving, carbon reduction, and safe and efficient degradation of VOCs, ambient temperature catalytic oxidation has become a hot topic for researchers. Firstly, this review systematically summarizes recent progress on the catalytic oxidation of VOCs with different types. Secondly, based on nanoparticle catalysts, cluster catalysts, and single-atom catalysts, we discuss the influence of structural regulation, such as adjustment of size and configuration, metal doping, defect engineering, and acid/base modification, on the structure-activity relationship in the process of catalytic oxidation at ambient temperature. Then, the effects of process conditions, such as initial concentration, space velocity, oxidation atmosphere, and humidity adjustment on catalytic activity, are summarized. It is further found that nanoparticle catalysts are most commonly used in ambient temperature catalytic oxidation. Additionally, ambient temperature catalytic oxidation is mainly applied in the removal of easily degradable pollutants, and focuses on ambient temperature catalytic ozonation. The activity, selectivity, and stability of catalysts need to be improved. Finally, according to the existing problems and limitations in the application of ambient temperature catalytic oxidation technology, new prospects and challenges are proposed.

Boosting the catalytic behavior and stability of a gold catalyst with structure regulated by ceria

In this work, a series of colloidal gold nanoparticles with controllable sizes were anchored on carbon nanotubes (CNT) for the aerobic oxidation of benzyl alcohol. The intrinsic influence of Au particles on the catalytic behavior was unraveled based on different nanoscale-gold systems. The Au/CNT-A sample with smaller Au sizes deserved a faster reaction rate, mainly resulting from the higher dispersion degree (23.5%) of Au with the available exposed sites contributed by small gold particles. However, monometallic Au/CNT samples lacked long-term stability. CeO2 was herein decorated to regulate the chemical and surface structure of the Au/CNT. An appropriate CeO2 content tuned the sizes and chemical states of Au by electron delivery with better metal dispersion. Small CeO2 crystals that were preferentially neighboring the Au particles facilitated the generation of Au-CeO2 interfaces, and benefited the continuous supplementation of oxygen species. The collaborative functions between the size effect and surface chemistry accounted for the higher benzaldehyde yield and sustainably stepped-up reaction rates by Au-Ce5/CNT with 5 wt% CeO2.

Enhanced photocatalytic performance of rhodamine B and enrofloxacin by Pt loaded Bi4V2O11: boosted separation of charge carriers, additional superoxide radical production, and the photocatalytic mechanism

Photocatalytic performance is influenced by two contradictory factors, which are light absorption range and separation of charge carriers. Loading noble metals with nanosized interfacial contact is expected to improve the separation and transfer of photo-excited charge carriers while enlarging the light absorption range of the semiconductor photocatalyst. Therefore, it should be possible to improve the photocatalytic performance of pristine nontypical stoichiometric semiconductor photocatalysts by loading a specific noble metal. Herein, a series of novel Pt-Bi4V2O11 photocatalysts have been successfully prepared via a surface reduction technique. The crystal structure, morphology, and photocatalytic performance, as well as photo-electron properties of the as-synthesized samples were fully characterized. Moreover, the series of Pt-Bi4V2O11 samples were evaluated to remove typical organic pollutants, rhodamine B and enrofloxacin, from aqueous solutions. The photoluminescence, quenching experiments and the electron spin resonance technique were utilized to identify the effective radicals during the photocatalytic process and understand the photocatalytic mechanism. The photocatalytic performance of Pt-Bi4V2O11 was tremendously enhanced compared with pristine Bi4V2O11, and there was additional ˙O2- produced during the photocatalytic process. This study deeply investigated the relation between the separation of charge carriers and the light harvesting, and revealed a promising strategy for fabricating efficient photocatalysts for both dyes and antibiotics.

Phosphatized mild-prepared-NiCo LDHs cabbage-like spheres exhibit excellent performance as a supercapacitor electrode

Phosphating treatment can increase the specific capacitance by 1.88 times without destroying the cabbage-like sphere structure of NiCo LDHs.

Hierarchical nanostructures self-assembled from δ-MnO2 ultrathin nanosheets and Mn3O4 octahedrons for efficient room-temperature HCHO oxidation

Self-assembling ultrathin active δ-MnO₂ nanosheets and Mn₃O₄ octahedrons into hierarchical texture enhances room-temperature formaldehyde oxidation at a low-level of Pt.

Highly Efficient MnO2/AlOOH Composite Catalyst for Indoor Low-Concentration Formaldehyde Removal at Room Temperature

Indoor formaldehyde from substandard furniture and decorative materials seriously endangers human health. How to remove effectively indoor formaldehyde with low concentration at room temperature is a challenging problem. Using a MnO₂/AlOOH composite by the MnO₂ modification as a catalyst provides an effective approach to solve this challenge. Here, a new type of MnO₂/AlOOH composite catalyst with high ability to remove indoor low-concentration formaldehyde was prepared by redox reaction at room temperature. A MnO₂/AlOOH composite with a homogeneous dispersion of MnO₂ has high specific surface area and a large amount of surface hydroxyl (-OH) which plays a major role in the adsorption of formaldehyde. A partially crystalline structure was observed in the composite, which contains multivalent Mn ions and a large number of vacancy defects. The surface -OH of composite shows strong oxidation activity through the charge exchange of multivalent Mn ions and vacancy defects. The composite has a higher ability to remove indoor low-concentration formaldehyde compared to the birnessite MnO₂ at room temperature. This study proposes a new idea for the improvement of catalytic performance in the structure and composition of the catalyst.

0D/2D CeO2 quantum dot/NiO nanoplate supported an ultralow-content Pt catalyst for the efficient oxidation of formaldehyde at room temperature

The 0D/2D CeO₂ quantum dot/NiO nanoplate supporting ultralow content of the Pt catalyst shows enhanced catalytic decomposition of formaldehyde at room temperature.

Bimetallic nickel molybdate supported Pt catalyst for efficient removal of formaldehyde at low temperature

Efficient removal of formaldehyde from indoor environments is of significance for human health. In this work, a typical binary transition metal oxide that could provide various oxidation states, β-NiMoO₄, was employed as a support to immobilize the active Pt component (Pt/NiMoO₄) for catalytic formaldehyde elimination at low ambient temperature (15°C). The results showed that the hydrothermal preparation temperature and time had a noticeable impact on the morphology and catalytic activity of the samples. The catalyst prepared with hydrothermal temperature of 150°C for 4 hr (Pt-150-4) exhibited superior catalytic activity and stability mainly due to its distinctly porous structure, relative abundance of adsorbed surface hydroxyls/water, and high oxidation ability, which resulted from the interaction of Pt with Ni and Mo of the bimetallic NiMoO₄ support. Our results might shed light on the rational design of multifunctional catalysts for removal of indoor air pollutants at low ambient temperature.

Hydroxyapatite-Supported Low-Content Pt Catalysts for Efficient Removal of Formaldehyde at Room Temperature

Indoor environmental quality directly affects the life quality and health of human beings, and therefore, it is highly vital to eliminate the volatile organic compounds especially formaldehyde (HCHO), which is regarded as one of the most common harmful pollutants in indoor air. Hydroxyapatite (HAP)-supported Pt (Pt/HAP) catalysts with a low content of Pt (0.2 wt %) obtained via hydrothermal and chemical reduction processes could effectively remove gaseous HCHO from the indoor environment at room temperature. The influence of modifier in the preparation on the catalyst activity was investigated. The HAP and HAP modified by sodium citrate and hexamethylenetetramine-supported 0.2 wt % Pt could completely decompose HCHO into CO2 and water, while HAP modified by sodium dodecyl-sulfate-supported Pt removed HCHO primarily via adsorption. The HAP modified by the sodium citrate catalyst exhibited superior catalytic performance of HCHO compared to the HAP and HAP modified by hexamethylenetetramine and sodium dodecyl-sulfate-supported Pt catalysts, which was mainly because of its higher surface Ca/P ratio providing more Lewis acidic sites (Ca2+) for co-operational capture of HCHO molecules and a larger amount of active oxygen species. Our results indicate that an optimized combination of functional supports and low-content noble metal nanoparticles could be a route to fabricate effective room-temperature catalysts for potential application in indoor air purification.