Remarkably enhanced catalytic activity by the synergistic effect of palladium single atoms and palladium-cobalt phosphide nanoparticles

Abstract

For the realization of commercially viable ethanol fuel cells, despite much safer than hydrogen gas, it is necessary to develop stable high-performance catalysts for ethanol electro-oxidation reaction (EOR). Unfortunately, current EOR catalysts are far from the expectation and suffer from fast activity degradation. Here we report palladium cobalt phosphide (Pd-Co2P) nanoparticles (NPs) with Pd single atoms (PdSAs) anchored on graphene oxide (GO) (denoted as Pd-Co2P-PdSAs@GO). Its EOR mass activity (10,520 mA/mgPd) is remarkably larger than any reported carbon-based precious metal catalysts including the benchmark Pd/C catalyst. To achieve high activity and stability, we systematically designed the catalyst with optimized elements ratio (Pd, Co/Ni/Fe, and P) and pyrolysis temperature together with electrochemical activation. The synergistic effect of charge-transfer between Pd and Co2P coexisting on the PdSAs@GO surface to shift the Pd d-band center promotes the bimetallic catalyst activity. The strong binding of PdSAs@GO with metals and the phosphide ligand stabilized NPs provide longterm durability. In-situ Raman analysis reveals that Co2P plays major roles in eliminating poisoning CO at neighboring Pd sites and retaining the catalytic activity even after 20 h.