Enhanced dry reforming of methane over NixCoy-HAP catalysts: Insights into the effect of Co species on carbon deposition and RWGS

Co and Ni are widely used to prepare bimetallic catalysts for dry reforming of methane (DRM) due to their comparable electronic configurations. In this study, a series of NixCoy-HAP catalysts were prepared, and by combining the characterization with XRD, H2-TPR, XPS, and TEM, the influence of Co incorporation on the redox properties, catalytic activity, catalytic stability, carbon deposition resistance and side reactions of the catalysts was evaluated. The results showed that both Ni and Co are homogeneously dispersed in the HAP structure by ion-exchange. The addition of Co enhances the reducibility of NixCoy-HAP and significantly improves the catalytic activity in the initial stage. Ni5Co1-HAP exhibits best catalytic stability in a 100-h long-term reaction accompanied by the deactivation of CH4 and CO2 with only 0.09% h−1 and 0.10% h−1, respectively. Characterization of the spent catalysts demonstrates that the decrease in activity of high Co content catalysts (Ni1Co5-HAP and Ni1Co10-HAP) is not due to carbon deposition, but rather that the addition of Co facilitates the RWGS side reaction. Process characterization of the catalysts in the CH4 one-component reaction indicates that an increase in the concentrates of one promotes a faster reduction of the other metal due to the strong electronic coupling of Ni and Co. These insights revealed here can pave the way for the preparation of Ni–Co bimetallic catalysts with high catalytic activity, robust resistance to carbon deposition and inhibition of a RWGS side reaction.