Design,Synthesis and Application of Phosphorus and Phosphorus-based Electrocatalysts

Author:Zhang Li Li

Supervisor:wang hai hui

Database:Doctor

Degree Year:2019

Download:56

Pages:150

Size:13645K

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Electrocatalytic energy storage and conversion technology is an important means to ensure the efficient and sustainable utilization of clean and renewable energy.In this paper,various electrochemical reactions in the energy storage and conversion device centered on the H2O,CO2 and N2 cycles are systematically reviewed,and,the design and research progress of electrocatalysts are introduced.In view of the two major problems of low activity and low stability of electrocatalysts in various cyclic applications,two strategies of increasing the number of active sites and improving the intrinsic catalytic performance of each activity site were designed.Specifically,a series of nanomaterials based on nonmetallic element P were synthesized,and their electracatalytic performance were studied.1.Inspired by the principle of“like dissolves like”,it is demonstrated that a member of the nitrogen family,phosphorus,can be used as an efficient nonmetallic active center for electrochemical nitrogen reduction.In order to release the intrinsic catalytic activity of phosphorus as much as possible,black phosphorus(BP)was used as the precursor of the catalyst,and the well-exfoliated few-layer black phosphorus nanosheets(FL-BP NSs)was prepared by a facile liquid exfoliation method,then abundant active sites were exposed to promote the adsorption and activation of nitrogen.The FL-BP NSs electrocatalyst can achieve a high ammonia yield of 31.37μg h-1 mg-1cat.and a maximum faradaic efficiency of 5.07%under ambient conditions.Density functional theory calculations revealed that the active orbital and electrons of zigzag and diff-zigzag type edges of FL-BP NSs enable selective electrocatalysis of N2 to NH3 via an alternating hydrogenation pathway.2.The nonmetallic-incorporated porous PtP alloy nanotube arrays(PtP NTAs)composed of interconnected nanocrystals were successfully synthesized via a facile electrodeposition method.Compared with the pure Pt nanotube arrays and the commercial Pt/C,the PtP NTAs exhibit a significantly enhanced electrocatalytic activity and stability for the ORR in an acidic medium.Particularly,the catalyst showed almost no degradation in ORR activity and only lost about 9%in ECSA after 10000 potential cycles.3.1D self-supported porous PtAuP alloy nanotube arrays(ANTAs)were synthesized via a facile electro-codeposition approach and present enhanced activity and improved resistance to CO poisoning through inhibiting CO formation(non-CO pathway)during the methanol oxidation reaction in acidic medium.This well-controlled Pt-/transition metal-/nonmetal ternary nanostructure exhibited a specific electroactivity twice as great as that of PtAu alloy nanotube arrays and Pt/C.At the same time,PtAuP ANTAs showed a higher ratio of forward peak current density(If)to backward peak current density(Ib)(2.34)than PtAu ANTAs(1.27)and Pt/C(0.78).The prominent If/Ib value of PtAuP ANTAs indicated that most of the intermediate species are electro-oxidized to carbon dioxide in the forward scan,which highlights the high electroactivity for methanol electro-oxidation.4.The P-Pd-CeO2 and PdO/Pd-CeO2 hollow spheres(HS)were prepared by template method for electrocatalyzing FAO reaction.The introduction of P can effectively reduce the oxidation potential of FAO on the P-Pd-CeO2 HS catalyst(peak potential at 0.152 V vs.SCE),which promote the complete oxidation of formic acid,then reduce the generation of intermediate toxic species.And,the presence of CeO2 not only can benefite the dispersion of P-Pd or PdO/Pd nanoparticles,but also promote the oxidation of toxic species adsorbed on the surface of Pd by OHads species adsorbed on the oxygen vacance of CeO2.Then,with enriched fresh active surface,the PdO/Pd-CeO2 HS reached a high FAO activity of 1620.0 mA mgpd-1,and the electrode can effectively avoid the loss of active metal Pd in the electrocycle.