Synergism of Ultrasmall Pt Clusters and Basic La₂O₂CO₃ Supports Boosts the Reverse Water Gas Reaction Efficiency

Abstract

the most promising routes of the artificial carbon cycle, has aroused widespread concern and paves a new way to sustainably produce fuels and fine chemicals, but a validated process is still lacking both conceptually and practically. [1a] As the most fundamental route of CO 2 hydrogenation, the reverse-water gas shift (RWGS) reaction offers a chance to overcome the challenges. [2] Despite the catalytic process being no longer mysterious, the specific reaction rate achieved currently is still far from the thermodynamic equilibrium, possibly owing to the difficulties in manipulating the surface state the of catalyst to simultaneously meet all the requirements of distinct steps involved. [3] The size of metal centers plays an essential role. [4] Conventional RWGS catalysts embedded with metal nanoparticles (NP) are favorable to the activation of CO 2 / H 2 reactants, contributing to an accelerated conversion rate, but it might also cause the problem of CO desorption, thus leading to over-hydrogenation. [5] In contrast, when scaling into a single atom (SA), besides the maximized metal utilization efficiency, the metal centers are commonly ionized, which can greatly weaken the adsorption strength of CO. [4a,c] However, single-atom metals without forming a complete crystal possess a poorer capacity of hydrogen dissociation compared with the nanoscale counterparts, which is unfavorable to activity. [6] That is because the active hydrogen species can not only directly involve in the catalysis, but also be responsible for creating oxygen vacancies (O V ) by reacting with the lattice oxygen of support, which is of great significance in CO 2 adsorption. [7] Therefore, it is eager to discover a new strategy for tailoring the surface state of catalysts aiming at achieving a better balance between CO 2 adsorption and CO desorption.Besides metal centers, the supports also give a considerable impact on RWGS performance. [8] Previous reports pointed out that basic oxides are favorable to CO 2 adsorption and metal dispersion compared with acidic and neutral oxides. [9] As a typical example, Nomura et al. demonstrated that a small amount of K 2 O can effectively improve the CO 2 conversion rate by accelerating CO 2 adsorption. [9c] However, the basicity of the catalyst cannot be too strong. Muroyama et al. revealed that Ni/ Y 2 O 3 exhibits more powerful capability in CO 2 to CH 4 conversion compared with Ni/La 2 O 3 . [10] That is because the key The reverse water-gas shift reaction (RWGS) has been regarded as a promising approach for fighting climate change caused by the excessive emission of the greenhouse gas CO 2 , but it still suffers from relatively poor low-temperature reactivity. Herein, a high-performance RWGS catalyst composed of ultrasmall Pt clusters (1.38 nm on average) anchored by La 2 O 2 CO 3 support (Pt NC /LOC), which possesses a record CO production rate of 2678 mol CO mol Pt −1 h −1 with nearly 100% CO selectivity at 300 °C, is reported. The specific activity is nearly 1.5 and 7.9 fold higher than tha...

Stabilizing Undercoordinated Zn Active Sites through Confinement in CeO2 Nanotubes for Efficient Electrochemical CO2 Reduction

“…The nanotube with confinement effect could stabilize the Zn δ + sites, and CeO 2 with the Ce 3 + /Ce 4 + redox could inhibit the electron accumulation around the unsaturated site and thus prevent the reduction degradation of active Zn δ + sites during CO 2 electrolysis. [25][26][27][28] The hollow core-shell structure Zn δ + /ZnO/CeO 2 with a high selectivity of 76.9 % at À 1.08 V vs. RHE toward CO product and the CO selectivity in a long-term stability test over 18 h. In situ characterization and theoretical studies demonstrate that the energy barrier for the formation of *COOH is thermodynamically reduced by Zn δ + sites. And the confinement strategy ensures the stability of Zn δ + species, which contributes to maintaining the CO selectivity in a long-term stability.…”

Effects of metal size on supported catalysts for CO2 hydrogenation

“…Pt-based catalysts are promising catalysts for the industrial RWGS process because of their excellent low-temperature activity (o270 1C), resistance to carbon deposition, and high CO selectivity at high temperatures. 71,72 However, limited by the high price and low natural abundance, Pt-based catalysts have not been used in the RWGS process on a large scale. One of the ways to solve this problem is to reduce the active center to the nanoscale as much as possible and even keep it highly dispersed at the atomic level.…”

“…The ultrasmall Pt clusters successfully integrated the unique surface states of single atoms and nanoparticles, thus achieving excellent catalytic performance. 71 Xing et al selected perovskite-type oxide SrTiO 3 as the support for constructing catalysts for CO 2 hydrogenation, and they found that the catalysts with SA sites (Pt 1 /SrTiO 3 ) exhibited higher CO selectivity than the catalysts with 2.72 nm NPs (Pt 7 /SrTiO 3 ). 74 They calculated the process of CO hydrogenation to CHO, and the reaction barriers for CO hydrogenation were 1.88 and 1.07 eV on Pt 1 /SrTiO 3 and Pt 7 /SrTiO 3 , respectively.…”

Defect-Driven Efficient Selective CO2 Hydrogenation with Mo-Based Clusters

“…CO is an important intermediate from CO 2 hydrogenation and can be used directly as fuel or as feedstock in tandem reactions for a diverse range of fuel products . A variety of noble metal-based catalysts have been developed for reverse water gas shift (RWGS) reactions in recent years, – but their high cost poses insurmountable challenges for commercial implementation. Non-noble metals for the RWGS reaction normally have poor activity and selectivity, especially at low temperatures, but there are exceptions, being highly dependent on the fine regulation of the local electronic structures for the active sites. – …”