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To mitigate the effect of CO2 on climate change, significant efforts have been made in the past few decades to capture CO2, which can then be further sequestered or converted into value-added compounds, such as methanol and hydrocarbons, by using thermochemical or electrocatalytic processes. However, CO2 capture and conversion have primarily been studied independently, resulting in individual processes that are highly energy-intensive and less economically viable due to high capital and operation costs. To enhance the overall process efficiency, integrating CO2 capture and conversion into a single system offers an opportunity for a more streamlined process that can reduce energy and capital costs. This strategy can be achieved by employing dual function materials (DFMs), which possess the unique capability to simultaneously adsorb and convert CO2. These materials combine basic metal oxides with active metal catalytic sites that enable both sorption and conversion functions. In this review paper, we focus on the recent strategies that utilize mixed metal oxides as DFMs. Their material design and characteristics, reaction mechanisms, as well as performance and limitations will be discussed. We will also address the challenges associated with this integrated system and attempt to provide insights for future research endeavors. [ABSTRACT FROM AUTHOR]

At present, passive NOx adsorbers (PNAs) represent one of the most effective technologies for addressing NOx emissions from diesel engines during cold-start periods. Conventional PNAs, which primarily consist of noble metals (such as Pt, Pd, and Ag) loaded on metal oxides or zeolites, share the common drawback of high production costs. Consequently, developing low-cost PNAs with outstanding NOx storage performance remains a significant challenge. In this study, a series of CuxBa5Ce adsorbents were synthesized using the impregnation method, and a monolithic adsorbent was employed to evaluate NOx storage and release performance. Techniques such as XRD, UV-Vis DRs, H2-TPR, XPS, and in situ DRIFTs confirmed the crucial roles of Cu and Ba in NOx storage and release. Specifically, the incorporation of Cu into CeO2 enhanced NOx storage performance. Moreover, in the Cu3Ba5Ce adsorbent, the addition of Ba not only introduced new storage sites and altered the stability of NOx adsorption species but also helped prevent the aggregation of CuO, thereby prolonging the complete NOx storage duration and satisfying desorption temperature requirements. The Cu3Ba5Ce adsorbent exhibited the most favorable NOx storage performance, including a complete NOx storage time of 135 s and a NOx storage efficiency exceeding 50% at 80 °C over a 10 min period. While PNAs loaded with noble metals, such as Pd/CeO2 and Pt/CeO2, exhibited NOx storage efficiencies below 50% after adsorbing for 5 min at 80 °C. Therefore, this research offered a crucial strategy for developing non-noble-metal-loaded, Ce-based PNAs. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction (SCR) of NO x with NH 3 has been widely used for the removal of NO x. Because of the inevitable disadvantages of conventional V 2 O 5 -WO 3 (MoO 3)/TiO 2 catalysts such as poor low-temperature SCR activity and toxicity of vanadium, as well as the high-cost and over-strong NH 3 adsorption of zeolite catalysts, the development of efficient and non-toxic metal oxide SCR catalysts is highly demanded. Previously, we have developed an environmentally-benign CeO 2 -SiO 2 mixed-oxide SCR catalyst (CeSi 2), which exhibited superior SO 2 resistance ability. However, the low-temperature SCR activity on CeSi 2 was not that satisfactory. In this work, we proposed a new strategy of Mo doping to improve the low-temperature SCR activity on CeSi 2 , which was very crucial for its practical application. By a simple co-precipitation method, a homogenous Mo-Ce-Si mixed-oxide catalyst was prepared. The Mo doping could significantly enhance the NH 3 -SCR activity on CeSi 2 below 250 °C, and the optimal catalyst was Mo 0.1 CeSi 2 , which could achieve 80% NO x conversion at 200 °C. Mo 0.1 CeSi 2 also exhibited superior N 2 selectivity and resistance to SO 2 /H 2 O poisoning. Via a series of characterizations, it was found that the redox properties and surface acidity on CeSi 2 by Mo doping, which accounted for the enhanced low-temperature NH 3 -SCR activity on Mo 0.1 CeSi 2. The reaction mechanism on Mo 0.1 CeSi 2 was also fully revealed by in situ DRIFTS experiments. This work provided a new insight for the development of efficient low-temperature SCR catalysts with superior SO 2 resistance ability. [Display omitted] • A homogeneous Mo-Ce-Si mixed-oxide catalyst was prepared. • Enhanced low-temperature NH 3 -SCR activity was achieved on Mo doped CeO 2 -SiO 2. • Mo-Ce-Si catalyst exhibited excellent resistance to SO 2 poisoning. • Surface acidity and redox properties of CeO 2 -SiO 2 were promoted by Mo doping. • NH 3 -SCR reaction on Mo-Ce-Si catalyst proceeds through E-R mechanism. [ABSTRACT FROM AUTHOR]

Understanding the nature of active sites on metal oxide catalysts in the selective catalytic reduction (SCR) of NO by NH 3 (NH 3 -SCR) is a crucial prerequisite for the development of novel efficient NH 3 -SCR catalysts. In this work, two CeO 2 -based SCR catalyst systems with diverse acidic metal oxides-CeO 2 interfaces, i.e., Nb 2 O 5 -CeO 2 (Nb 2 O 5 /CeO 2 and CeO 2 /Nb 2 O 5) and WO 3 -CeO 2 (WO 3 /CeO 2 and CeO 2 /WO 3), were prepared and used to reveal the relationship between NH 3 -SCR activity and surface acidity/redox properties. In combination with the results of the NH 3 -SCR activity test and various characterizations, it was found that the NH 3 -SCR performance of Nb 2 O 5 -CeO 2 and WO 3 -CeO 2 catalysts was highly dependent on the strong interactions between the redox component (CeO 2) and acidic component (Nb 2 O 5 or WO 3), as well as the amount of paired redox-acid sites. From a quantitative perspective, an activity-surface acidity/redox property relationship was proposed. For both Nb 2 O 5 -CeO 2 and WO 3 -CeO 2 catalysts systems operated at the more concerned low-temperature range (200 °C), the NH 3 -SCR activity in low NO x conversion region (< 40%) was mainly dominated by the surface acidity of catalysts, while the NH 3 -SCR activity in high NO x conversion region (> 40%) was more determined by redox properties. [Display omitted] • Nb 2 O 5 -CeO 2 and WO 3 -CeO 2 catalysts with tuned redox-acid property were synthesized. • Paired redox-acid sites formed through strong interaction between Nb 2 O 5 /WO 3 and CeO 2. • NH 3 -SCR activity was well controlled by the paired redox-acid sites. • Surface acidity and redox property were investigated from a quantitative perspective. • A clear surface acidity/redox property-activity relationship was established. [ABSTRACT FROM AUTHOR]

Surfactant-free and low Au loading Cu2O@Au and Au hollow cubes, based on electrodeposited Cu2O cubes as sacrificed templates, were prepared by means of a galvanic replacement reaction (GRR). The electrocatalytical performance of the as-prepared catalysts towards carbon dioxide (CO2) electrochemical reduction was evaluated. The experimental results show that Cu2O@Au catalyst can convert CO2 to carbon monoxide (CO) with a maximum Faradaic efficiency (FE) of ~ 30.1% at the potential of − 1.0 V (vs. RHE) and is about twice the FE of the other catalysts at the same potential. By comparison, such electrocatalytical enhancement is attributed to the metal-oxide interface in Cu2O@Au. [ABSTRACT FROM AUTHOR]

Modifying CeO 2 with acid sites is a common strategy for designing efficient catalysts for the selective catalytic reduction of NO x by NH 3 (NH 3 -SCR of NO x). However, the effect of acid metal oxide modification on the SO 2 resistance of CeO 2 has not been well revealed. In this work, it was found that the SO 2 resistance of CeO 2 modified with several acid metal oxides (i.e. , MoO 3 , WO 3 and Nb 2 O 5), followed an order of Mo/CeO 2 ≥ W/CeO 2 > Nb/CeO 2. Further systematic characterizations revealed that Mo-OH and W-OH on CeO 2 as Brønsted acid sites could better inhibit the SO 2 adsorption and the sulfation of active sites than highly dispersed NbO x mainly as Lewis acid sites because NH 4 + coordinated to Brønsted acid sites could help trap SO 2 to form ammonium sulfates rather than metal sulfates. The findings in this work provided important guidance for the design of efficient catalysts with superior SO 2 resistance performance. [Display omitted] • CeO 2 modified with varying acid metal oxides showed different resistance to SO 2. • Highly dispersed MoO 3 or WO 3 could better shield CeO 2 from SO 2 poisoning than Nb 2 O 5. • Mo and W sites as Brønsted acid sites could better inhibit the SO 2 adsorption on CeO 2. • SO 2 could interact with both highly dispersed Nb 2 O 5 and CeO 2 on Nb/CeO 2. • A strategy for designing efficient catalysts with superior resistance to SO 2 was provided. [ABSTRACT FROM AUTHOR]