4d-2p-4f Gradient Orbital Coupling Enables Tandem Catalysis for Simultaneous Abatement of N2O and CO on Atomically Dispersed Rh/CeO2 Catalyst

N2O and CO coexist in various industrial and mobile sources. The synergistic reaction of N2O and CO to generate N2 and CO2 has garnered significant research interest, but it remains extremely challenging. Herein, we constructed an atomically dispersed Rh-supported CeO2 catalyst with asymmetric Rh-O-Ce sites through gradient Rh 4d-O 2p-Ce 4f orbital coupling. This design effectively regulates the 4f electron states of Ce and promotes the electron filling of the O 3π* antibonding orbital to facilitate N-O bond cleavage. Near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) reveals that CO reacts with the surface-adsorbed O* generated by N2O decomposition through self-tandem catalysis, accelerating the rate-limiting step in N2O decomposition and activating the synergistic reaction of N2O and CO at temperatures as low as 115 °C. This work can guide the development of high-performance catalysts using the strategy of high-order orbital hybridization combined with the tandem concept to achieve versatile catalytic applications.

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.

Rhodium Nanoparticles Incorporated Mesoporous Silica as an Active Catalyst for Cyclohexene Hydrogenation under Ambient Conditions

Rhodium (Rh) nanoparticles were embedded in the mesopores of TUD-1 siliceous material and denoted as Rh-TUD-1. Five samples of Rh-TUD-1 were prepared with different loadings of Rh that ranged from 0.1 to 2 wt% using the sol-gel technique. The prepared samples were characterized by means of several chemical and physical techniques. The obtained characterization results show the formation of highly distributed Rh0 nanoparticles with an average size ranging from 3 to 5 nm throughout the three-dimensional silica matrix of TUD-1. The catalytic activity of the prepared catalysts was evaluated in the solvent-free hydrogenation of cyclohexene to cyclohexane at room temperature using 1atm of hydrogen gas. The obtained catalytic results confirm the high activity of Rh-TUD-1, in which a turn over frequency (TOF) ranging from 4.94 to 0.54 s−1 was obtained. Moreover, the change in reaction temperature during the reaction was monitored, and it showed an obvious increase in the reaction temperature as an indication of the spontaneous and exothermic nature of the reactions. Other optimization parameters, such as the substrate/catalyst ratio, and performing the reaction under non-ambient conditions (temperature = 60 °C and hydrogen pressure = 5 atm) were also investigated. Rh-TUD-1 exhibited a high stability in a consecutive reaction of five runs under either ambient or non-ambient conditions.