Devoting Attention to China's Burgeoning Industrial N2O Emissions

Progress and challenges in nitrous oxide decomposition and valorization

Nitrous oxide (N2O) decomposition is increasingly acknowledged as a viable strategy for mitigating greenhouse gas emissions and addressing ozone depletion, aligning significantly with the UN's sustainable development goals (SDGs) and carbon neutrality objectives. To enhance efficiency in treatment and explore potential valorization, recent developments have introduced novel N2O reduction catalysts and pathways. Despite these advancements, a comprehensive and comparative review is absent. In this review, we undertake a thorough evaluation of N2O treatment technologies from a holistic perspective. First, we summarize and update the recent progress in thermal decomposition, direct catalytic decomposition (deN2O), and selective catalytic reduction of N2O. The scope extends to the catalytic activity of emerging catalysts, including nanostructured materials and single-atom catalysts. Furthermore, we present a detailed account of the mechanisms and applications of room-temperature techniques characterized by low energy consumption and sustainable merits, including photocatalytic and electrocatalytic N2O reduction. This article also underscores the extensive and effective utilization of N2O resources in chemical synthesis scenarios, providing potential avenues for future resource reuse. This review provides an accessible theoretical foundation and a panoramic vision for practical N2O emission controls.

Boosting N2O Decomposition by Fabricating the Cs-O-Co Structure over Co3O4 with Single-Layer Atoms of Cs

Developing effective catalysts for N2O decomposition at low temperatures is challenging. Herein, the Cs-O-Co structure, as the active species fabricated by single-layer atoms of Cs over pure Co3O4, originally exhibited great catalytic activity of N2O decomposition in simulated vehicle exhaust and flue gas from nitric acid plants. A similar catalytic performance was also observed for Na, K, and Rb alkali metals over Co3O4 catalysts for N2O decomposition, illustrating the prevalence of alkali-metal-promotion over Co3O4 in practical applications. The catalytic results indicated that the TOF of Co3O4 catalysts loaded by 4 wt% Cs was nearly 2 orders of magnitude higher than that of pure Co3O4 catalysts at 300 °C. Interestingly, the conversions of N2O decomposition over Co3O4 catalysts doped by the same Cs loadings were significantly inhibited. Characterization results indicated that the primary active Cs-O-Co structure was formed by highly orbital hybridization between the Cs 6s and the O 2p orbital over the supported Co3O4 catalysts, where Cs could donate electrons to Co3+ and produce much more Co2+. In contrast, the doped Co3O4 catalysts were dominated by Cs2O2 species; meanwhile, CsOH species was generated by adsorbed water vapor led to a significant decrease in catalytic activity. In situ DRIFTS, rigorous kinetics, and DFT results elaborated the reaction mechanism of N2O decomposition, where the direct decomposition of adsorbed N2O was the kinetically relevant step over supported catalysts in the absence of O2. Meanwhile, the assistance of adsorbed N2O decomposition by activated oxygen was observed as the kinetically relevant step in the presence of O2. The results may pave a promising path toward developing alkali-metal-promotion catalysts for efficient N2O decomposition.

Shifts in the high-resolution spatial distribution of dissolved N2O and the underlying microbial communities and processes in the Pearl River Estuary

Estuaries are significant sources of the ozone-depleting greenhouse gas N2O. However, owing to large spatial heterogeneity and discrete measurements, N2O emissions from estuaries are considerably uncertain. Microbial processes are disputed in terms of the dominant N2O production under severe human disturbance. Herein, combining real-time and high-resolution measurements with bioinformatics analysis, we accurately mapped the consecutive two-dimensional N2O distribution in the Pearl River Estuary (PRE), China, and revealed its underlying microbial mechanisms. Both the horizontal and vertical distributions of N2O concentrations varied greatly at fine scales. Supersaturated N2O concentrations (9.1 to 132.2 nmol/L) in the surface water decreased along the estuarine salinity gradient, with several emission hotspots scattering upstream. The vertical N2O distribution showed marked differences from complete mixing upstream to incomplete mixing downstream, with constant or changeable concentrations with increasing depth. Furthermore, spatially varied denitrifying and nitrifying microorganisms controlled the N2O production and distribution in the PRE, with denitrification playing the dominant role. The nirK-type and nirS-type denitrifying bacteria were the primary producers of N2O in the water and sediment columns, respectively. In addition, substrate concentration (NO3- and DOC) regulated N2O production by affecting key microbial processes, while physical influences (water-mass mixing and salt wedges) reshaped N2O distribution. With these information, a conceptual model of estuarine N2O production and distribution was constructed to generalize the possible biochemical processes under environmental constraints, which could provide insights into the N2O biogeochemical cycle and emission mitigation from a mechanistic perspective.

Elongating the role of renewable energy and sustainable foreign direct investment on environmental degradation

Climatic variations and GHG emissions are the most debated issues of the current age economically, socially, politically and environmentally. An internationally legally binding treaty on climate change, the "Paris Agreement" is followed by G-8 countries to maintain environmental sustainability with green development. The research investigates the relationship of GHG emissions with renewable energy (RE), foreign direct investment (FDI), total population (TP), and trade (TR). The time span of 22 years is used for analytical purposes covering the period from 2000 to 2021 b y addressing the literary gap. The analytical procession found total population and trade increase GHG emissions because of its modern fundamental layers toxic human activities and polluted trade practices. The decreasing behavior toward GHG emissions has been determined by FDI and RE. The findings of this research have confirmed the long-run relationship among variables. They are evidence that the eco-innovative steps by G-8 countries significantly reduce GHG emissions directly or indirectly. Furthermore, the analytical outcomes indicate that innovative green development in renewable energy sector can reduce the GHG emissions pressure from this sector and contribute to net zero emissions. The extracting results have suggested policies for environmental practitioners and economic developers.

Strong Electronic Orbit Coupling between Cobalt and Single-Atom Praseodymium for Boosted Nitrous Oxide Decomposition on Co3O4 Catalyst

Nitrous oxide (N₂O) has gained increasing attention as an important noncarbon dioxide greenhouse gas, and catalytic decomposition is an effective method of reducing its emissions. Here, Co₃O₄ was synthesized by the sol-gel method and single-atom Pr was confined in its matrix to improve the N₂O decomposition performance. It was observed that the reaction rate varied in a volcano-like pattern with the amount of doped Pr. A N₂O decomposition reaction rate 5-7.5 times greater than that of pure Co₃O₄ is achieved on the catalyst with a Pr/Co molar ratio of 0.06:1, and further Pr doping reduced the activity due to PrO_x cluster formation. Combined with X-ray photoelectron spectroscopy, X-ray absorption fine structure, density functional theory and in situ near-ambient pressure X-ray photoelectron spectroscopy, it was demonstrated that the single-atom doped Pr in Co₃O₄ generates the "Pr 4f-O 2p-Co 3d" network, which redistributes the electrons in Co₃O₄ lattice and increases the t_2g electrons at the tetracoordinated Co²⁺ sites. This coupling between the Pr 4f orbit and Co²⁺ 3d orbit triggers the formation of a 4f-3d electronic ladder, which accelerates the electron transfer from Co²⁺ to the 3π* antibonding orbital of N₂O, thus contributing to the N-O bond cleavage. Moreover, the energy barrier for each elementary reaction in the decomposition process of N₂O is reduced, especially for O₂ desorption. Our work provides a theoretical grounding and reference for designing atomically modified catalysts for N₂O decomposition.