Bifunctional low-Pt content nanocatalysts supported on carbons functionalized with a Cu-organometallic compound: Tailoring of d-band center with high catalytic activity for electrochemical oxygen reactions

Abstract

In this study, Vulcan XC-72 (C) and sewage sludge-derived biocarbon (SSB) are functionalized with mesitylcopper (Cu-mes) and implemented to produce the low-Pt content and thus low-cost (5 wt %) Pt/CCu-mes10, Pt/CCu-mes20, Pt/SSBCu-mes10, and Pt/SSBCu-mes20 nanocatalysts. This approach facilitates the generation of various functional groups along with the CuO and Cu2O phases. The nanocatalysts show the formation of the PtCu3 alloy, with the two first having an atomic fraction of Cu alloyed (XCu) of 55 and 67%, respectively. Pt/CCu-mes10 shows a comparable catalytic activity for the oxygen reduction reaction (ORR) before and after an accelerated degradation test (ADT) to 20 wt % Pt/C and 5 wt % Pt/C. It also shows the highest performance for the oxygen evolution reaction (OER), with remarkable electrochemical stability. The outstanding performance of Pt/CCu-mes10 is attributed to the presence of Cu-phases, its high degree of alloying and its d-band center which favorably promotes the adsorption of O-species and their further reaction. Specifically, the PtCu3 alloy promotes the kinetics of the reactions by modulating the electronic properties of Pt and creating dual active sites. Meanwhile, Pt/SSB demonstrates an encouraging performance for the reactions before ADT, with electrochemical parameters similar to those of 20 wt % Pt/C. However, its stability is poor, with low catalytic activity after ADT. Therefore, it is found that there is a significant effect of the electrochemical behavior of the carbon support on the performance and stability of the nanocatalysts. The potential application of Pt/CCu-mes10 in water splitting devices is identified.