Alloying Ni–Cu Nanoparticles Encapsulated in SiO₂ Nanospheres for Synergistic Catalysts in CO₂ Reforming with Methane Reaction

Abstract

In this work, we studied CO2 reforming with the methane (CRM) reaction over Ni–Cu alloy nanoparticles encapsulated in SiO2 nanospheres, for which combinational functions of alloy effect, size effect, metal-support interaction, and confinement effect exhibited high performance, good sintering resistance, and trace carbon deposition in CRM. The appropriate Cu-addition catalysts 0.2Cu–Ni@SiO2 and 0.5Cu–Ni@SiO2 had smaller NiCu alloy nanoparticles and a stronger metal-support interaction, exhibiting a better performance than the excessive Cu-addition catalysts 1.5Cu–Ni@SiO2 and 3Cu–Ni@SiO2 having Cu clusters and a weaker metal-support interaction. The best synergy of alloy effect, size effect, confinement effect, and metal-support interaction in the 0.5Cu–Ni@SiO2 catalyst contributed to the highest rates of CH4 and CO2 in CRM reported so far. This work demonstrates the importance of appropriate Cu addition in Ni–Cu@SiO2 catalysts, and the synergy for perfectly resolving sintering and carbon deposition in CRM.

Ni–Cu Alloy Nanoparticles Confined by Physical Encapsulation with SiO2 and Chemical Metal–Support Interaction with CeO2 for Methane Dry Reforming

“…The spectrum of Cu 2p gives two characteristic peaks of Cu 0 at 934.3 and 947.5 eV (Figure B), corresponding to Cu 2p3/2 and Cu 2p1/2, respectively. In a previous study, binding energies of Cu 2p3/2 and Ni 2p3/2 were measured at 932.4 and 852.8 eV in the referenced samples Cu/SiO 2 and Ni@SiO 2 , respectively . The blue shifts of both Ni 2p3/2 and Cu 2p3/2 in the (2Ni–Cu/CeO 2 )@SiO 2 sample mostly originated from their alloy formation and MSI with ceria. − Xin et al measured a higher Ni 2p signal on Ni 6 Co 4 /SBA than on Ni 10 /SBA, which was assigned to the charge transfer from Ni to Co due to the formation of Ni–Co alloy .…”

“…33−36 In a previous work, we developed a Ni−Cu@SiO 2 catalyst with an optimized Ni/Cu weight ratio of 6 for MDR. 37 The best synergy of alloy effect, size effect, confinement effect, and MSI in the 0.5Cu−Ni@SiO 2 catalyst contributed to the highest rates of CH 4 and CO 2 . However, the Ni−Cu alloy size was marginally increased from 3.0 to 3.5 nm, and 0.3 wt % carbon deposits was still detected on the used catalyst.…”

“…In a previous work, we developed a Ni–Cu@SiO 2 catalyst with an optimized Ni/Cu weight ratio of 6 for MDR . The best synergy of alloy effect, size effect, confinement effect, and MSI in the 0.5Cu–Ni@SiO 2 catalyst contributed to the highest rates of CH 4 and CO 2 .…”

Design Strategy, Synthesis, and Mechanism of Ni Catalysts for Methane Dry Reforming Reaction: Recent Advances and Future Perspectives

“…Encapsulating Ni nanoparticles provides a great opportunity to limit metal sintering, this is because the encapsulation hinders migration of Ni atoms from one catalyst unit to another catalyst unit, exhibiting a confinement effect for the enhancement of sintering resistance. This protects Ni nanoparticles from Ostwald ripping and aggregation . Meantime, because of the close contact between the confined Ni nanoparticles and the encapsulating material, the chemical environments of the Ni nanoparticles would be modulated because of their strong metal–support interaction, which benefits MDR performance.…”

“…This protects Ni nanoparticles from Ostwald ripping and aggregation. 57 Meantime, because of the close contact between the confined Ni nanoparticles and the encapsulating material, the chemical environments of the Ni nanoparticles would be modulated because of their strong metal−support interaction, which benefits MDR performance. However, mass-transfer resistance might be caused by the reactant molecules' diffusion from external to internal in the encapsulation catalyst; developing encapsulation Ni catalysts with rich pores is thus very necessary to eliminate mass transfer.…”