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Catalytic conversion of CO2 to CO via the reverse water gas shift (RWGS) reaction has been identified as a promising approach for CO2 utilization and mitigation of CO2 emissions. Bare Pt shows low activity for the RWGS reaction due to its low oxophilicity, with few research works having concentrated on the inverse metal oxide/Pt catalyst for the RWGS reaction. In this work, MnOx was deposited on the Pt surface over a SiO2 support to prepare the MnOx/Pt inverse catalyst via a co-impregnation method. Addition of 0.5 wt% Mn to 1 wt% Pt/SiO2 improved the intrinsic reaction rate and turnover frequency at 400 °C by two and twelve times, respectively. Characterizations indicate that MnOx partially encapsulates the surface of the Pt particles and the coverage increases with increasing Mn content, which resembles the concept of strong metal–support interaction (SMSI). Although the surface accessible Pt sites are reduced, new MnOx/Pt interfacial perimeter sites are created, which provide both hydrogenation and C-O activation functionalities synergistically due to the close proximity between Pt and MnOx at the interface, and therefore improve the activity. Moreover, the stability is also significantly improved due to the coverage of Pt by MnOx. This work demonstrates a simple method to tune the oxide/metal interfacial sites of inverse Pt-based catalyst for the RWGS reaction. [ABSTRACT FROM AUTHOR]

Ultra‐low molecular weight (ULMW) CO2‐polyols with well‐defined hydroxyl end groups represent useful soft segments for the preparation of high‐performance polyurethane foams. However, owing to the poor proton tolerance of catalysts towards CO2/epoxide telomerization, it remains challenging to synthesize ULMW yet colorless CO2‐polyols. Herein, we propose an immobilization strategy of constructing supported catalysts by chemical anchoring of aluminum porphyrin on Merrifield resin. The resulting supported catalyst displays both extremely high proton tolerance (≈8000 times the equivalents of metal centers) and independence of cocatalyst, affording CO2‐polyols with ULMW (580 g mol−1) and high polymer selectivity (>99 %). Moreover, the ULMW CO2‐polyols with various architectures (tri‐, quadra‐, and hexa‐arm) can be obtained, suggesting the wide proton universality of supported catalysts. Notably, benefiting from the heterogeneous nature of the supported catalyst, colorless products can be facilely achieved by simple filtration. The present strategy provides a platform for the synthesis of colorless ULMW polyols derived from not only CO2/epoxides, but also lactone, anhydrides etc. or their combinations. [ABSTRACT FROM AUTHOR]

Reverse water gas shift (RWGS) reaction is an attractive approach to convert CO2 with renewable H2 to produce CO. However, this reaction is always accompanied by undesirable methanation reaction lowering the CO selectivity, particularly, at low reaction temperature and on Ni catalysts. Herein, a strategy of deposition of inert Ag on the surface of Ni to block methanation reaction during RWGS for selective conversion of CO2 toward CO was reported. Characterizations showed that in contrast to formation of bulk Ni−Ag alloy, both Ag particle and highly dispersed Ag are direct contacting with Ni particle. Surface Ag modifies the property of Ni geometrically and electronically, resulting in reduced accessible surface Ni sites and Ni ensemble size, as well as electron transfer from Ni to Ag. Consequently, both the amount and strength of CO adsorption are reduced, which facilitates CO desorption and reduces CO methanation activity. The Ag modification tunes Ni/SiO2 from selective methanation to selective RWGS, with 100 % CO selectivity on Ni‐0.3 Ag/SiO2 (Ag/Ni=0.3) at 400 °C with gas hourly space velocity (GHSV) >300 L g−1 h−1 and CO selectivity is >80.7 % even at a low GHSV of 15 L g−1 h−1. Moreover, the Ni‐0.3 Ag/SiO2 appears to be very stable for RWGS reaction. [ABSTRACT FROM AUTHOR]

Catalytic reduction of CO 2 with renewable H 2 to CO via the reverse water gas shift (RWGS) reaction is an attractive approach to recycle CO 2 and control net emission of CO 2 to atmosphere. However, low activity and high CH 4 selectivity at low temperatures limited the practical implementation of the reaction. Herein, Pt-Re/SiO 2 catalysts with varying amount of Re were prepared with co-impregnation and tested for the RWGS reaction. Characterization results indicated that the oxophilic ReO x (0 ≤ x ≤ 3.5) located in close proximity to Pt particle, modified the surface of Pt by both partial coverage and electronic interaction, resulting in the reduced number of sites for and weakened strength of CO adsorption. At 400 °C, the turnover frequency (2.30 s−1) on the optimal Pt-Re/SiO 2 catalyst (Pt/Re = 1.91) is 3.9 times higher than that on Pt/SiO 2 under differential conditions, and the apparent activation energy is lowered. In contrast to Re/SiO 2 which produces significant amount of CH 4 , the CO selectivity on Pt-Re/SiO 2 maintained > 96.2 % under integral conditions. Reaction order analysis revealed that Pt facilitates H 2 activation whereas the oxophilic ReO x enhances CO 2 adsorption and activation. The perimeter sites at the Pt/ReO x interface with a balanced hydrogenation and C-O cleavage properties synergistically improve the RWGS activity while inhibiting CH 4 production. [Display omitted] • ReO x (0 ≤ x ≤ 3.5) modified the surface of Pt by both partial coverage and electronic interaction. • ReO x modification weakened CO adsorption on Pt and enhanced CO selectivity (> 96.2 %). • TOF of RWGS on optimal Pt-Re/SiO 2 (2.30 s−1) is 3.9 times higher than that on Pt/SiO 2. • Reaction kinetic analysis revealed Pt and ReO x activate H 2 and CO 2 , respectively. • The synergy of Pt and ReO x enhanced RWGS activity and inhibited CH 4 formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni is unselective for RWGS due to competition from methanation during CO 2 reduction. • CO 2 reduction follows RWGS to CO and then methanation to CH 4. • MoO x modifies the surface of Ni by both geometric and electronic effects. • Bimetallic NiMo catalyst with Mo/Ni of 0.1 is selective for methanation. • Bimetallic NiMo catalyst with Mo/Ni of 1 is selective for RWGS. Catalytic reduction of CO 2 to CO via reverse water gas shift (RWGS) reaction provides a feasible approach to utilize CO 2 , since CO can be further converted to various versatile products through the syngas routes. Ni-based catalysts are low cost and have a high activity for CO 2 reduction but are nonselective for RWGS due to competition from methanation. In this work, we demonstrated that surface modification of Ni by MoO x can be tailored to tune the reactions of RWGS and methanation. The addition of MoO x improves Ni dispersion through strong interactions whereas partially reduced MoO x modifies the surface of Ni particles through both geometric coverage and electronic modification. No CO adsorption was observed at room temperature on the NiMo catalyst with a Mo/Ni ratio of 1, confirmed by density functional theory calculation. Tracking product evolution showed that CO 2 is first reduced to CO through RWGS on the Ni catalysts and methane is a product of CO hydrogenation. Apparent activation energy analysis indicates that the overall reaction is controlled by CO desorption. Addition of a small amount of Mo (Mo/Ni ratio of 0.1) shifts the reaction further to methanation selective with ∼100% CH 4 selectivity as MoO x aids in the activation of both CO 2 and CO. In contrast, the addition of a large amount of Mo (Mo/Ni ratio of 1) shifts the reaction to RWGS selective with a CO selectivity > 94%. This is attributed to the enhanced CO desorption from the surface as a result of MoO x modification. [ABSTRACT FROM AUTHOR]