Shuai Lyu,Li Wang,Jianghao Zhang,Chen Liu,Junming Sun,Bo Peng,Yong Wang,Kenneth G. Rappé,Yuhua Zhang,Jinlin Li,Lei Nie
In order to understand the role of Co catalysts with different phases on Fischer–Tropsch synthesis, single-phase face-centered-cubic (fcc) and hexagonal-close-packed (hcp) Co were synthesized via a two-step approach, involving the formation of single-phase CoO materials followed by reduction in H2. The physicochemical properties of Co catalysts were thoroughly characterized by XRD, SEM, TEM, TPR, and H2 chemisorption. It was found that hcp-Co exhibits higher activity on hydrocarbon formation than fcc-Co in Fischer–Tropsch synthesis. For both catalysts, CO dissociation was suggested as the rate-determining step, on which hcp-Co presents ca. 40 kJ mol–1 lower activation energy than fcc-Co, in agreement with a reported computational study. As a result, hcp-Co is concluded to be the preferable phase for rational catalyst design.
Hao Liu,Shan Yang,Jinxing Mi,Chuanzhi Sun,Jianjun Chen,Junhua Li
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.
Yunhao Liu,Qingpeng Cheng,Shuaishuai Lyu,Xincheng Li,Song Song,Tong Ding,Ye Tian,Xingang Li
In the realm of Fischer-Tropsch synthesis (FTS), the escalating cost of cobalt has spurred interest in Co-Fe bimetallic catalysts as substitutes for monometallic Co catalysts. Unfortunately, it is difficult to clarify specific functions and interactions of the two phases, as investigating catalysts in a unified dimension of both metal and support is still a challenge. Herein, we realize precise control over synthesizing nitrogen-doped carbon materials supported bimetallic catalysts containing CoFe alloy and Co + Fe 2 C dual active phases. The catalysts are comprehensively characterized to address the above problem by excluding the influence of metal sizes and support properties. Our findings reveal that compared to metallic Co alone and Co + Fe 2 C dual active phases, the Co-Fe interaction in CoFe alloy with electron transfer from Fe to Co optimizes reactant adsorption behaviors through achieving a larger number of strongly adsorbed CO per active site to increase the density of C* adsorbates and a higher surface CO/H 2 ratio to inhibit the hydrogenation of CH x * intermediates for chain termination, as well as an appropriate ability for CO adsorption/ dissociation. These advantages collectively enhance both CO activation and C-C coupling, and consequently, the CoFe/NC (CoFe alloy) catalyst exhibits the superior catalytic performance in the cobalt space–time yield in C 5+ products (3011.2 g C5+ kg Co −1 h −1 ), which surpasses the Co/NC (monometallic Co) and Co + Fe/NC (Co + Fe 2 C dual active phases) by 2.2 times and 2.4 times, respectively. This study serves as a promising route for the development of efficient and low-cost bimetallic catalysts through the strategic arrangement of multiple active phases for various reactions.
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