Remarkably efficient and stable Ni/Y2O3 catalysts for CO2 methanation: Effect of citric acid addition

Citric acid has been investigated for preparing the highly dispersed nickel catalysts on Y2O3 support. A highly enhanced methanation activity with the high CO2 conversion of 92 % and CH4 selectivity of 100 % was obtained over Ni/Y2O3 with optimum addition of citric acid at 350 degrees C. The citric acid additives during the preparation are found to influence the size of nickel nanoparticles and the interaction of metal and support, as estimated by various techniques, which, in turn, to correlated with the catalytic performance. In situ DRIFTS spectra further indicate the importance of small Ni particles on formation of carbonates and formate species as key intermediates and the subsequent hydrogenation of those species into methane. This study proposes that the Y-O-Ni interfacial structure formed by the strong Ni and Y2O3 interaction at high citric acid addition is of prime importance for the formation of methane, benefiting from the more abundant basic sites and metallic Ni to enable CO2 activation and hydrogenation of key intermediates by effective H-2 dissociation respectively. This work provides a new design strategy for developing highly efficient composite CO2 methanation catalysts by control of the metal particle size and charge transfer via metal/support interface.