Improving the carbon resistance of reforming Ni catalysts by alloying with Rh

The most widely used industrial method for H2 production is hydrocarbon steam reforming over Ni-based catalysts. However, under the low O:C ratios optimal for overall efficiency, Ni catalysts deactivate due to carbon deposition. Carbon deposition occurs via either hydrocarbon decomposition (CnH2n+2 → nC + (n+1)H2) or CO disproportionation (2CO → CO2 + C) reactions. The addition of the second metal to the Ni surface can increase carbon tolerance by introducing variations of carbon chemistry over the catalyst surface. In the present study, supported Ni and Rh/Ni catalysts were synthesized and tested for hydrocarbon steam reforming. Carbon analysis on the spent catalysts illustrates that the carbon deposition is significantly reduced in the presence of Rh. In order to provide insights into the mechanistic changes introduced by Rh, carbon diffusion and oxidation processes over Ni and Rh/Ni alloy surfaces were simulated by DFT calculations.