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Boosting the performance of Ni/Al2O3 for the reverse water gas shift reaction through formation of CuNi nanoalloys
Gioria, Esteban; Ingale, Piyush; Pohl, Felix; Naumann d'Alnoncourt, Raoul; Thomas, Arne; Rosowski, Frank
Ni supported on alumina is extensively employed as a catalyst for the reverse water gas shift reaction. However, the formation of inactive Ni aluminates and the high selectivity to methane affects the performance of these catalysts, especially at low reaction temperatures. In this study, Cu is employed as an effective enhancer of the catalytic performance, promoting the reducibility of Ni, and suppressing methane production through the formation of stable CuNi nanoalloys. The synergy between both metals suppresses consecutive hydrogenation, reaching conversions close to equilibrium and 100% selectivity to carbon monoxide. At 500 °C, the CO yield of the Cu25Ni75/Al2O3 catalyst was twice that of Ni/Al2O3, with only half the hydrogen consumption. The formation of CuNi nanoalloys was confirmed by HAADF STEM–EDS, without segregation in monometallic phases even after 30 h time on stream. Similarly, Cu50Ni50/Al2O3 remained alloyed after the reaction. However, the catalytic activity decreased due to sintering, in agreement with a higher Cu content. This effect was significantly more pronounced for Cu75Ni25/Al2O3 and Cu/Al2O3, with formation of large particles and consequent loss of active surface area.
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