Boosting Electrocatalytic Nitrate Reduction through Enhanced Mass Transfer in Cu-Bipyridine 2D Covalent Organic Framework Films.

Electrocatalytic nitrate reduction (NORR) is a promising method for pollutant removal and ammonia synthesis and involves the transfer of eight electrons and nine protons. As such, the rational design of catalytic interfaces with enhanced mass transfer is crucial for achieving high ammonia yield rates and Faradaic efficiency (FE). In this work, we incorporated a Cu-bipyridine catalytic interface and fabricated crystalline 2D covalent organic framework films with significantly exposed catalytic sites, leading to improved FE and ammonia yield (FE=92.

Challenges and Perspectives of Environmental Catalysis for NO Reduction.

Environmental catalysis has attracted great interest in air and water purification. Selective catalytic reduction with ammonia (NH-SCR) as a representative technology of environmental catalysis is of significance to the elimination of nitrogen oxides (NO ) emitting from stationary and mobile sources. However, the evolving energy landscape in the nonelectric sector and the changing nature of fuel in motor vehicles present new challenges for NO catalytic purification over the traditional NH-SCR catalysts.

Strong metal oxide-zeolite interactions during selective catalytic reduction of nitrogen oxides.

In response to the stricter EU VII emission standards and the "150 ℃ challenge", selective catalytic reduction by ammonia (NH-SCR) catalysts for motor vehicles are required to achieve high NO conversion below 200 °C. Compounding metal oxides with zeolites is an important strategy to design the low-temperature SCR catalysts. Here, we original prepared Cu-SSZ-13 @ MnGdO (Cu-Z @ MGO), which achieved over 90% NO conversion and 95% N selectivity at 150 ℃.

Selective Synergistic Catalytic Elimination of NO and CHSH via Engineering Deep Oxidation Sites against Toxic Byproducts Formation.

NO and CHSH as two typical air pollutants widely coexist in various energy and industrial processes; hence, it is urgent to develop highly efficient catalysts to synergistically eliminate NO and CHSH. However, the catalytic system for synergistically eliminating NO and CHSH is seldom investigated to date. Meanwhile, the deactivation effects of CHSH on catalysts and the formation mechanism of toxic byproducts emitted from the synergistic catalytic elimination reaction are still vague.

Boosting SO-Resistant NO Reduction by Modulating Electronic Interaction of Short-Range Fe-O Coordination over FeO/TiO Catalysts.

SO-resistant selective catalytic reduction (SCR) of NO remains a grand challenge for eliminating NO generated from stationary combustion processes. Herein, SO-resistant NO reduction has been boosted by modulating electronic interaction of short-range Fe-O coordination over FeO/TiO catalysts. We report a remarkable SO-tolerant FeO/TiO catalyst using sulfur-doped TiO as the support.

Low-Temperature Combustion of Toluene over Cu-Doped SmMnO Mullite Catalysts via Creating Highly Active Cu-O-Mn Sites.

Catalytic combustion of volatile organic compounds (VOCs) at low temperatures is still an urgent issue to be solved. Herein, low-temperature combustion of toluene over Cu-doped SmMnO mullite catalysts via creating highly active Cu-O-Mn sites has been originally demonstrated. Cu-doped SmMnO mullite catalysts exhibited 90% conversion of toluene at 206 °C and displayed robust stability even in the presence of water.

SO-Tolerant Catalytic Reduction of NO via Tailoring Electron Transfer between Surface Iron Sulfate and Subsurface Ceria.

Currently, SO-induced catalyst deactivation from the sulfation of active sites turns to be an intractable issue for selective catalytic reduction (SCR) of NO with NH at low temperatures. Herein, SO-tolerant NO reduction has been originally demonstrated via tailoring the electron transfer between surface iron sulfate and subsurface ceria. Engineered from the atomic layer deposition followed by the pre-sulfation method, the structure of surface iron sulfate and subsurface ceria was successfully constructed on CeO/TiO catalysts, which delivered improved SO resistance for NO reduction at 250 °C.

SO- and HO-Tolerant Catalytic Reduction of NO at a Low Temperature via Engineering Polymeric VO Species by CeO.

Selective catalytic reduction (SCR) of NO over VO-based oxide catalysts has been widely used, but it is still a challenge to efficiently reduce NO at low temperatures under SO and HO co-existence. Herein, SO- and HO-tolerant catalytic reduction of NO at a low temperature has been originally demonstrated via engineering polymeric VO species by CeO. The polymeric VO species were tactfully engineered on Ce-VO composite active sites via the surface occupation effect of Ce, and the obtained catalysts exhibited remarkable low-temperature activity and strong SO and HO tolerance at 250 °C.

Synergistic Catalytic Elimination of NO and Chlorinated Organics: Cooperation of Acid Sites.

The synergistic catalytic removal of NO and chlorinated volatile organic compounds under low temperatures is still a big challenge. Generally, degradation of chlorinated organics demands sufficient redox ability, which leads to low N selectivity in the selective catalytic reduction of NO by NH (NH-SCR). Herein, mediating acid sites introducing the CePO component into MnO/TiO NH-SCR catalysts was found to be an effective approach for promoting chlorobenzene degradation.

Unraveling SO-tolerant mechanism over Fe(SO)/TiO catalysts for NO reduction.

Developing low-temperature SO-tolerant catalysts for the selective catalytic reduction of NO is still a challenging task. The sulfation of active metal oxides and deposition of ammonium bisulfate deactivate catalysts, due to the difficult decomposition of the as-formed sulfate species at low temperatures (<300 °C). In recent years, metal sulfate catalysts have attracted increasing attention owing to their good catalytic activity and strong SO tolerance at higher temperatures (>300°C); however, the SO-tolerant mechanism of metal sulfate catalysts is still ambiguous.

Alkali-Resistant Catalytic Reduction of NO by Using Ce-O-B Alkali-Capture Sites.

Reducing the poisoning effect arising from alkali metals over catalysts for selective catalytic reduction (SCR) of NO by NH is still an urgent issue to be solved. Herein, alkali-resistant NO reduction over B-doped CeO/TiO catalysts (Ce-B/TiO) with Ce-O-B alkali-capture sites was originally demonstrated. It was noted that boron was confirmed to be doped into the lattice of CeO to form the Ce-O-B structure.

SO-Tolerant NO Reduction by Marvelously Suppressing SO Adsorption over FeCeVO Catalysts.

SO-tolerant selective catalytic reduction (SCR) of NO at low temperature is still challenging. Traditional metal oxide catalysts are prone to be sulfated and the as-formed sulfates are difficult to decompose. In this study, we discovered that SO adsorption could be largely restrained over FeCeVO catalysts, which effectively restrained the deposition of sulfate species and endowed catalysts with strong SO tolerance at an extremely low temperature of 240 °C.

Alkali-Resistant NO Reduction over SCR Catalysts via Boosting NH Adsorption Rates by In Situ Constructing the Sacrificed Sites.

Currently, improving the alkali resistance of vanadium-based catalysts still remains as an intractable issue for the selective catalytic reduction of NO with NH (NH-SCR). It is generally believed that the decrease in adsorbed NH species deriving from the declined acidic sites is the chief culprit for the deactivation of alkali-poisoned catalysts. Herein, alkali-resistant NO reduction over SCR catalysts via boosting NH adsorption rates was originally demonstrated by in situ constructing the sacrificed sites.

Self-Protected CeO-SnO@SO/TiO Catalysts with Extraordinary Resistance to Alkali and Heavy Metals for NO Reduction.

Reducing the poisoning effect of alkali and heavy metals over ammonia selective catalytic reduction (NH-SCR) catalysts is still an intractable issue, as the presence of K and Pb in fly ash greatly hampers their catalytic activity by impairing the acidity and affecting the redox properties of the catalysts, leading to the reduction in the lifetime of SCR catalysts. To address this issue, we propose a novel self-protected antipoisoning mechanism by designing SO/TiO superacid supported CeO-SnO catalysts. Owing to the synergistic effect between CeO and SnO and the strong acidity originating from the SO/TiO superacid, the catalysts show superior catalytic activity over a wide temperature range (240-510 °C).

Alkali and Phosphorus Resistant Zeolite-like Catalysts for NO Reduction by NH.

At present, the deactivation of selective catalytic reduction (SCR) catalysts caused by the coexistence of alkali metal and phosphorus (P) remains an urgent problem and lacks corresponding strategies against catalyst poisoning. Herein, a novel zeolite-like Ce-SiAlO catalyst derived from an ultrasmall nanozeolite EMT precursor was synthesized without organic templates at ambient temperature. This catalyst was able to maintain above 95% NO conversion in the 270-540 °C temperature range.

Tailored Alkali Resistance of DeNO Catalysts by Improving Redox Properties and Activating Adsorbed Reactive Species.

It is still challenging to develop strongly alkali-resistant catalysts for selective catalytic reduction of NO with NH. It is generally believed that the maintenance of acidity is the most important factor because of neutral effects of alkali. This work discovers that the redox properties rather than acidity play decisive roles in improving alkali resistance of some specific catalyst systems.

Unraveling the Unexpected Offset Effects of Cd and SO Deactivation over CeO-WO/TiO Catalysts for NO Reduction.

It is challenging for selective catalytic reduction (SCR) of NO by NH due to the coexistence of heavy metal and SO in the flue gas. A thorough probe into deactivation mechanisms is imperative but still lacking. This study unravels unexpected offset effects of Cd and SO deactivation over CeO-WO/TiO catalysts, potential candidates for commercial SCR catalysts.

Selective Catalytic Reduction of NO with NH by Using Novel Catalysts: State of the Art and Future Prospects.

Selective catalytic reduction with NH (NH-SCR) is the most efficient technology to reduce the emission of nitrogen oxides (NO) from coal-fired industries, diesel engines, etc. Although VO-WO(MoO)/TiO and CHA structured zeolite catalysts have been utilized in commercial applications, the increasing requirements for broad working temperature window, strong SO/alkali/heavy metal-resistance, and high hydrothermal stability have stimulated the development of new-type NH-SCR catalysts. This review summarizes the latest SCR reaction mechanisms and emerging poison-resistant mechanisms in the beginning and subsequently gives a comprehensive overview of newly developed SCR catalysts, including metal oxide catalysts ranging from VO, MnO, CeO, and FeO to CuO based catalysts; acidic compound catalysts containing vanadate, phosphate and sulfate catalysts; ion exchanged zeolite catalysts such as Fe, Cu, Mn, etc.

SO-Tolerant Selective Catalytic Reduction of NO over Meso-TiO@FeO@AlO Metal-Based Monolith Catalysts.

It is an intractable issue to improve the low-temperature SO-tolerant selective catalytic reduction (SCR) of NO with NH because deposited sulfates are difficult to decompose below 300 °C. Herein, we established a low-temperature self-prevention mechanism of mesoporous-TiO@FeO core-shell composites against sulfate deposition using experiments and density functional theory. The mesoporous TiO-shell effectively restrained the deposition of FeSO and NHHSO because of weak SO adsorption and promoted NHHSO decomposition on the mesoporous-TiO.

FeO-CeO@AlO Nanoarrays on Al-Mesh as SO-Tolerant Monolith Catalysts for NO Reduction by NH.

Currently, selective catalytic reduction of NO with NH in the presence of SO is still challenging at low temperatures (<300 °C). In this study, enhanced NO reduction was achieved over a SO-tolerant Fe-based monolith catalyst, which was originally developed through in situ construction of AlO nanoarrays (na-AlO) on the monolithic Al-mesh by a steam oxidation method followed by anchoring FeO and CeO onto the na-AlO@Al-mesh composite by an impregnation method. The optimum catalyst delivered more than 90% NO conversion and N selectivity above 98% within 250-430 °C as well as excellent SO tolerance at 270 °C.

Dual Promotional Effects of TiO-Decorated Acid-Treated MnO Octahedral Molecular Sieve Catalysts for Alkali-Resistant Reduction of NO .

Alkali metals generated during waste incineration in power stations are not conducive to the control of nitrogen oxide (NO ) emission. Hence, improved selective catalytic reduction of NO with ammonia (NH-SCR) in the presence of alkali metals is a major issue for practical NO removal. In this work, we developed a novel TiO-decorated acid-treated MnO octahedral molecular sieve (OMS-5(H)@TiO) catalyst with improved alkali-resistant NO reduction at low temperature, and the dual promotional effects of OMS-5(H)@TiO catalysts were clarified.

Improved NO Reduction in the Presence of SO by Using FeO-Promoted Halloysite-Supported CeO-WO Catalysts.

Currently, selective catalytic reduction (SCR) of NO with NH in the presence of SO by using vanadium-free catalysts is still an important issue for the removal of NO for stationary sources. Developing high-performance catalysts for NO reduction in the presence of SO is a significant challenge. In this work, a series of FeO-promoted halloysite-supported CeO-WO catalysts were synthesized by a molten salt treatment followed by the impregnation method and demonstrated improved NO reduction in the presence of SO.

Coke-resistant defect-confined Ni-based nanosheet-like catalysts derived from halloysites for CO reforming of methane.

In this study, halloysites, one of the most abundant clays, with hollow nanotube features were reconstructed by selectively etching silica from the outermost layer of the halloysites associated with unzipping the nanotubes to nanosheets via ball milling, and then, nickel nanoparticles were confined by the resulting defects in the nanosheets to boost charge transfer by a wet impregnation method. The obtained materials were developed as coke-resistant defect-confined Ni-based nanosheet-like catalysts for CO2 reforming of methane (CRM) for the first time. The as-prepared catalyst exhibited good coke and sintering resistance performance in CRM, and especially, there was almost no loss of activity even after a 20 h stability test due to the strong interaction between the Ni nanoparticles and the support.

From nano- to macro-engineering of oxide-encapsulated-nanoparticles for harsh reactions: one-step organization via cross-linking molecules.

A strategy of "macro-micro-nano" organization is reported for embedding oxide-encapsulated-nanoparticles onto monolithic substrates in one-step with the aid of molecularly defined cross-linking agents. Such catalysts, with enhanced heat/mass transfer and high permeability, are qualified for several harsh reaction processes such as CH/VOC abatement, gas-phase hydrogenation of dimethyl oxalate and oxidative dehydrogenation of ethane.

Structured Pd-Au/Cu-fiber catalyst for gas-phase hydrogenolysis of dimethyl oxalate to ethylene glycol.

Galvanic co-deposition of 0.5 wt% Au and 0.1 wt% Pd on a microfibrous-structure using 8 μm Cu-fibers delivers a Pd-Au/Cu-fiber catalyst, which is highly active, selective and stable for the hydrogenolysis of dimethyl oxalate to ethylene glycol.