Synthesis And Electrochemical Properties Of Heteroatom-Modified Copper Single Atom Catalysts

In order to solve the fossil energy crisis and environmental pollution problems,great attentions have been attracted to develop clean and renewable energy sources,among which fuel cells and metal-air cells are the most widely studied.In these devices,oxygen reduction reactions(ORR)are involved,which is the core reactions on the cathode of energy conversion devices.Pt-based materialsare widely used as commercial ORR catalysts,but their high cost and poor stability have prevented their widespread commercial application.Therefore,the development of new efficient,stable and inexpensive catalysts to replace Pt/C has become one of the important research directions nowadays.In this paper,two types of heteroatomdoped copper monatomic catalysts were designed and successfully synthesized using the synthesis method of spontaneous polymerization of pyrrole monomer and one-piece doping of copper tetrasulfonate phthalocyanine.The main elements are as follows.(1)Copper ions triggered the polymerization of pyrrole monomers to form a coppernitrogen-carbon precursor.Then,the completely mixed precursors were added to the tube furnace together with phytic acid for pyrolysis to obtain heteroatomic nitrogen-phosphorus co-doped copper monatomic catalysts.The temperature of pyrolysis was varied to obtain CuN/P-C-X series catalysts.A variety of experimental characterizations were used to analyze the active sites of the catalysts and to investigate the effect of temperature on the elemental content of the catalysts as well as the N elemental species.Cu-N/P-C-700 has the best ORR activity with a half-wave potential of 0.87 V(vs.RHE),which is superior to commercial Pt/C and Cu-N-C-700 catalysts.The electrochemical stability of Cu-N/P-C-700 in ORR and the practical application performance in Zn-Air batteries are also significantly better than Pt/C,indicating that Cu-N/P-C-700 is a bifunctional catalyst with good electrochemical performance.Density functional theory calculations demonstrate that the introduction of heteroatomic phosphorus has a significant structural improvement and electrochemical performance enhancement on Cu-N-C-700 catalysts.(2)Copper tetrasulfonate phthalocyanine as a copper and sulfur source was doped into a metal zeolite imidazole ester structure,and then the doping ratio of copper tetrasulfonate phthalocyanine to metal zinc salt was changed.Finally,the Cu NSC-Ts-X catalysts were produced by pyrolysis at high temperature.Cu NSC-Lcy-X and Cu NSC-Pc S-X catalysts were prepared using additional copper sources and sulfur sources.The active sites in the catalyst were explored and verified using various characterization methods such as XRD,TEM and XPS.Cu NSC-Ts-40 possessed the best ORR performance,with Cu NSC-Ts-40 reaching an onset potential and half-wave potential of 1.00 V and 0.87 V.Cu NSC-Ts-40 also exhibited good electrochemical performance in Zn-Air batteries tests.The introduction of heteroatomic sulfur has been demonstrated to have an enhancing effect on the ORR performance using density functional theory calculations.