Ziheng Li,Junxin Guo,Haoze Liu,Dule Huhe,Zhao Wang
Despite their high methanol selectivity in CO2 hydrogenation, In2O3-based catalysts still face limitations in CO2 conversion and long-term stability. This work addresses these challenges by designing a highly dispersed Pd/In2O3 catalyst supported on self-pillared silicalite-1 (SP-S-1) zeolite. The well-defined channels and abundant surface silanol groups of SP-S-1 effectively anchor and disperse In2O3 nanoparticles. This structure also spatially isolates Pd species, which prevents their sintering and inhibits the formation of inactive Pd–In alloys. Comprehensive characterization reveals that the strong metal-support interaction stabilizes oxygen vacancies and prevents over-reduction of In3+ species, which are crucial for CO2 activation and methanol selectivity. The optimized Pd/In2O3/SP-S-1 catalyst achieves a methanol space-time yield of 2.57 gMeOH·gIn+Pd-1·h-1 at 300 °C, approximately five times higher than that of the unsupported counterpart. More importantly, it demonstrates high stability, retaining 95% of its initial activity after 100 hours on stream, far outperforming the unsupported catalyst. This work highlights zeolite confinement as a versatile strategy for designing robust and efficient CO2-to-methanol catalysts.
Zhongjie Cai,Jiajun Dai,Wen Li,Kok Bing Tan,Zhongliang Huang,Guowu Zhan,Jiale Huang,Qingbiao Li
Utilization of CO2 and its conversion to value-added chemicals are highly desirable to alleviate the environmental concerns caused by the massive anthropogenic CO2 emission. Although In2O3/Pd have been employed as efficient catalysts for hydrogenation of CO2 to methanol, the electronic effects by strong metal–support interaction (SMSI) between Pd and In2O3 are poorly understood, which is greatly affected by the morphology of In2O3. Herein, we use MIL-68(In) nanorod as a morphological template for the synthesis of hollow In2O3 nanotubes (h-In2O3) and the preparation of supported Pd catalysts for CO2 hydrogenation to methanol. Interestingly, loading Pd on h-In2O3 showed a much higher performance than In2O3 with other morphologies, which exhibited almost unchanged CO2 conversion of 10.5%, methanol selectively of 72.4%, and methanol space-time yield of 0.53 gMeOH h–1 gcat–1 over 100 h on stream at 3 MPa and 295 °C. After in-depth characterizations, we found that the different electronic properties of Pd species on In2O3 can be finely tuned by diverse synthetic conditions, which were responsible for high activity and stability. The molar fraction of Pd2+ species in the h-In2O3/Pd catalyst reached 67.6%, 3.2 times that of the In2O3@Pd catalyst (21.3%), due to the different surface chemistry of In2O3. Density function theory results indicated that the Pd donated more electrons to the curved In2O3 (222) surface than the pristine surface, and Pd2+ was critical to facilitate H2 adsorption and formation of the surface oxygen vacancy. This work demonstrates that controlling the morphology of In2O3 can modify both the Pd electronic property and SMSI between Pd and In2O3, which are the origins of the high catalytic performance.
Zhongming Wang,Hang Yuan,Siting Chen,Yong Jia,Lina Guo,Hong Wang,Wenxin Dai
The progressive transfer of photogenerated electrons between the catalyst components and reactants is of great significance for photocatalysis. Amorphous Pd (Pd A ) and oxygen vacancies (V O s) were simultaneously introduced in Pd-In 2 O 3 exploiting hydrogen-induced amorphization effects; 0.6 wt% Pd-In 2 O 3 exhibited a 4.5-fold increase in activity and a 3.2-fold higher selectivity toward CH 3 OH + CO (63.62 %) compared with In 2 O 3 . Multiple in situ techniques and theoretical calculations revealed that intercomponent electron transfer channels were established via various interface structures formed between Pd A or crystalline Pd (Pd C ) and In 2 O 3 ; Pd A acted as electronic pump, facilitating the transfer and separation of photogenerated electrons, resulting in their subsequent enrichment on the surface of Pd A . Simultaneously, Pd A acted as electron-donating adsorption site for H 2 O, increasing the number of electrons received by H 2 O, further inhibiting the competitive adsorption of H 2 O and CO 2 on V O sites, and promoting the hydrogen evolution reaction. Additionally, the electronic coupling between Pd C and V O s could significantly decrease the electron-donating ability of V O s, reducing the number of electrons received by CO 2 , thus effectively regulating the degree of CO 2 reduction. This study employs Pd A /Pd C and V O s to synergistic optimize the progressive transfer of photogenerated electrons, and presents a novel approach for elucidating the catalytic mechanism.
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