Impregnating Rhodium(0) Sites through Zeolite-Y Templation in a Hybrid Rh–Ni Catalyst for Alcohol Electro-Oxidation with Low CO Poisoning

Two hybrid electrocatalysts formulated as Rh/RhOx-Ni(OH)2-rGO and Rh/RhOx-Ni(OH)2-Y/rGO were synthesized using zeolite-Y and reduced graphene oxide (rGO) as solid support and hard templating agents. The hybrid composites served as effective electrocatalysts for the electrochemical oxidation of both methanol and ethanol. X-ray photoelectron spectroscopic analysis predicted for the creation of metallic rhodium, Rh(0), sites that helped in reducing the CO poisoning during electrocatalytic decomposition of the C1 and C2 alcohols. The zeolite-Y-embedded electrocatalyst, Rh/RhOx-Ni(OH)2-Y/rGO, showed high CO tolerance in comparison to Rh/RhOx-Ni(OH)2-rGO and Pt/C. This was further evident from the CO stripping experiment. The zeolite-Y matrix was found to have significant impact in enhancing the current density and durability of the electrocatalysts in both methanol and ethanol oxidation reaction (MOR and EOR) by stabilizing the low valent Rh species. The maximum current density in the case of MOR was found to be 5.6 A/mg, while that in the case of EOR was found to be 7.1 A/mg. The zeolite-Y-supported electrocatalyst exhibited stability up to 1000 cycles, which was retained for 13.8 h during MOR/EOR without any significant loss in the current density. The creation of mesoporous channels in zeolite-Y after its post-modification helped in high mass transfer and allowed to follow a diffusion-controlled mechanism. The linear relationship between current density and the square root of the scan rate also suggested a diffusion-controlled process. The catalysts also exhibited good methanol and ethanol tolerance with the maximum concentration up to 4 and 3 M, respectively.