Zou Jijun research group of Tianjin University: development of iron-based electrocatalytic oer catalyst based on spin state regulation

Lead oxygen generation reaction (OER) is an important anode reaction which widely exists in electrocatalytic decomposition water, photocatalytic decomposition water, N 2 reduction, CO 2 reduction and rechargeable metal air battery Its ultra-high overpotential is an important factor restricting the energy conversion efficiency of the above processes Many non noble metal efficient catalysts, such as LDH, perovskite, spinel, anti spinel, rock salt, etc., of which the Group VIII Fe, Co, Ni are the most active With the rapid development and application of batteries and electronic devices, precious metal resources and Co, Ni, etc are drying up day by day It is predicted that by 2030, there will be a serious shortage of CO, Ni resources (nature, 2018, 559 (7715), 467) Therefore, it is of great significance to develop excellent iron-based oer catalysts Recently, the research group of Zou Jijun of Tianjin University reported a method to achieve excellent oer activity of iron-based catalyst through spin state regulation Based on the most abundant transition metal elements Ti and Fe in the earth's crust, the atom level dispersed loading of Fe (III) on the surface of ultra-thin titanium oxide was realized by the adsorption oxidation strategy, and the spin state regulation of Fe (III) was realized by the interaction between them Professor Zou Jijun is the corresponding author of the article, and doctoral students Shen Guoqiang and Zhang Rongrong are the co first authors of the article The relevant research was published on Angewandte Chemie International Edition (DOI: 10.1002/anie.201913080) Zou Jijun research group of Tianjin University is subordinate to the Department of chemical technology, the Key Laboratory of the Ministry of education of advanced fuels and chemical propellants, and the Key Laboratory of green synthesis and transformation education The main research directions are: (1) the design of high efficiency electrocatalyst; (2) the development of new photocatalyst materials; (3) the synthesis and application of high performance aerospace fuel At present, the team has 15 doctors and 20 masters Undertake a number of national defense science and engineering Commission and enterprise cooperation projects The research group has long been committed to the research of non noble metal efficient catalysts, and has made a series of achievements in metal defect photocatalyst, electrocatalyst, spin state controlled decomposition water catalyst, etc (j.am.chem.soc., 2015, 137, 2975; nano energy, 2014, 9, 71; nano energy, 2016, 28, 296; ACS catalyst, 2018, 8, 3803; Appl Catal B-Environ   2019 , 244 , 536; Adv Energy Mater   2019 , 9 ,1901505）。
Prof Zou Jijun, Chair Professor of School of chemical engineering, Tianjin University, doctoral supervisor, deputy director of Key Laboratory of Ministry of education of advanced fuels and chemical propellants, deputy editor of RSC advances, leader of science and technology innovation of "ten thousand talents plan", young Changjiang Scholar of Ministry of education, winner of national excellent youth, outstanding young talents of national defense science and technology "Ten thousand people plan" is a top talent for young people He has successively presided over more than 20 projects of national and provincial ministries and commissions, such as the National Natural Science Foundation of China, the science and Technology Commission of the Military Commission, the science and Technology Bureau of national defense, and the Ministry of equipment He has published more than 120 papers in J am Chem SOC, angel Chem Int ed., adv mater., ACS catalyst., AIChE J, chem Eng SCI., etc., and obtained 15 authorized invention patents in the United States and China Contact: JJ ou zou@tju.edu.cn Introduction to Associate Professor Pan Lun, Associate Professor Pan Lun, doctoral supervisor and "young backbone teacher of Beiyang scholars" of Tianjin University As the person in charge, he presided over National Natural Science Fund project, national major science and technology special subject, science and Technology Commission, equipment pre research of Ministry of education, Tianjin Natural Science Fund, enterprise entrusted project, etc as the backbone of the project, he participated in national major science and technology special project, National Natural Science Fund, China Pakistan joint fund, Tianjin Natural Science Fund key fund, etc.; 2 At J am Chem SOC., adv mater., nano energy, ACS Nano, adv energy mater., ACS catalyst., adv SCI., appl Catalyst B, etc SCI journals have published more than 50 papers, including 3 cover papers; the total number of citations is more than 3000, H factor is 32; 3 Two national invention patents have been authorized, one PCT patent has been applied, and two national patents have been applied; 4 Successively went to the United States, Canada, Pakistan and other places to attend international conferences for many times, and made invitation reports Leading research achievements: the development of iron-based electrocatalytic oer catalyst based on spin state regulation Fe is an important element in the traditional non noble metal oer catalyst Fe Co Ni oxide / hydroxide The introduction of Fe (III) can significantly improve the oer activity of Ni (OH) 2 and CO (OH) 2, but the mechanism of the increase of catalyst activity, even whether Ni / Co or Fe (III) is the active site of the reaction, has been controversial Due to the special electronic structure of 3D 5-half-full-d orbital, Fe (III) in Fe (III) based oxides and hydroxides usually shows an intrinsic high spin state, and its e g orbital electronic filling degree is ~ 2.0, resulting in poor oer activity (Science, 2011, 334 (6061): 1383) However, in the Fe Co Ni mixed system, Fe (III), as a low content doping element, usually exists in the system in the state of atom level dispersion Inspired by this, in the absence of CO and Ni, the author designed the catalyst with atom level dispersion Fe (III) as the catalytic active site, and realized the advantage of no CO and Ni over noble metals RuO 2 and IrO 2 in alkaline condition Synthesis of high efficiency catalyst
Figure 1  DFT calculations (a-c) Side view model for DFT calculation of Fe-TiO 2  (a), Fe 2 O 3  (b) and TiO 2  (c) models after structural optimization (d) TDOS and projected DOS, and the dashed lines represent the d -band centers of Ti 3d  and Fe 3d (e-f) Projected Fe 3d  (e) and Ti 3d  (f) DOS of selected atoms in The model (source: angelw Chem Int ed.) firstly, using density functional theory (DFT), the author studied the electronic structure properties of titanium oxide, iron oxide and titanium oxide supported atom level dispersion Fe (III) (FE TiO 2) from the theoretical point of view From the total DOS diagram, it can be seen that the introduction of Fe (III) can produce significant d-orbital hybridization, and introduce a new energy level near the Fermi energy level, effectively reducing the band gap width and ohmic resistance; secondly, there is a strong interaction between Fe-TiO2, and the d-band centers of Fe (III) and Ti (IV) in Fe-TiO2 are close to each other compared with the pure phase of iron oxide and titanium oxide From the DOS diagram of Fe (III), it can be seen that the electrons below the Fermi level of pure iron oxide are filled in the full high spin state, and Fe (III) in Fe-TiO 2 is obviously transformed into the low spin state, which indicates that the lower e g orbital filling degree is favorable for oer process
Figure 2  (a) Schematic illustration of synthesis (b) The high-resolution HAADF-STEM image with spherical aberration correction of Fe-UTN, insert bar is 2 nm (c-f), EDS-mapping images of Fe-UTN in Ti (c), O (d), Fe (e) and overlay (f), Based on the above theoretical research results, the author synthesized the Fe (I I I) - TiO 2 catalyst with high loading and atom level dispersion Referring to the value of hydrolysis KSP of different metal ions, the hard to hydrolyze Fe (II) metal brine solution was chosen as the precursor to control only surface adsorption without subsequent hydrolysis Meanwhile, the adsorbed Fe (II) on the surface could also be completely oxidized to Fe (III) during drying in air Through this strategy, Fe (III) catalysts were successfully prepared Titanium oxide supported iron oxide nanoparticles were obtained by using trivalent iron as precursor Fe (III) dispersed at atomic level was observed in HAADF-STEM obtained by spherical difference electron microscopy By high resolution EDS mapping, the distribution of Ti, O and Fe was highly coincident, thus confirming its uniform loading state It is obvious that the binding energy of Fe (III) moves to a higher level and that of Ti (IV) moves to a lower level, which is consistent with the d-band center shift in DFT calculation The complete superparamagnetic Fe (III) species, which is different from the common iron oxide, are also observed in the magnetic hysteresis curve and Mossbauer spectrum In particular, there are some species other than high spin Fe (III) in the Mu spectral fitting results, whose valence state is still trivalent Combined with the relevant literature, it is inferred that the low spin Fe (III) species Figure 3 (a-b) XANES spectra (a) and Fourier transformed Fe K-edge EXAFS spectra (b) (C-D) temperature dependence inverse sensitivities (c) and O 2-TPD (d) of synthesized materials The chemical structure and spin state of the catalyst were analyzed By fitting the coordination structure, it is not only proved that the atom level loading of Fe (III) and the bond length become shorter due to the change of spin state By fitting the zfc-fc data with Curie's law, the change of electronic filling degree of e g was analyzed quantitatively Furthermore, the adsorption capacity of different catalysts for oxygen-containing substances was characterized by O 2-TPD Through the mutual confirmation of e g electronic filling degree and DFT calculation, it was proved that adjusting the loading state to adjust the spin state was an important means to optimize the oer activity of Fe (III)
Figure 4  ( a ) Polarization curves, ( b ) Tafel slopes, (c) electrical impact spectroscopy and (d) time dependent current density current of synthesized catalyst on glass electron DFT calculation predicted that Fe (III) dispersed at atomic level has lower overpotential, smaller Tafel slope and lower electrochemical impedance In particular, Fe UTN shows better oer activity than the noble metals RuO2 and IrO2, and it is also the best oer catalyst without noble metals and cobalt nickel Conclusion: Zou Jijun group developed a simple strategy of adsorption oxidation for the synthesis of highly loaded atom level dispersed Fe (III) catalyst Through the strong interaction between the two, the spin state regulation of Fe (III) was realized, and then the preparation of excellent oer catalyst based on a large number of metal elements in the crust was realized This synthesis method has a good reference for the preparation of high loading monoatomic catalyst, and also has a good inspiration for the high efficiency electrocatalytic and photocatalytic oxygen production catalyst Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information website, chembeangoapp, chembeango official micro blog, CBG information wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the representative research groups in China, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.