Tianjin University student Zheng Xueli, a Ph.D. student from the School of Materials Science and Engineering, has published an article entitled “Homogeneously dispersed, multimetal oxygen-evolving catalysts” in Science journal. Zheng Xueli participated in a dual program between Tianjin University and the University of Toronto, in Canada. During she received joint training from the School of Materials and Engineering of Tianjin University and the University of Toronto, she with the research team in Canada developed a room-temperature synthesis to produce gelled oxy-hydroxide materials with an atomically homogeneous metal distribution. The research achievement was published in Science and Zheng Xueli equally contributed as a first author.
Efficient, cost-effective and long-lived electrolysers are a crucial missing piece along the path to fuels synthesized with renewable electricity. Earth-abundant first-row (3d) transition-metal-based catalysts have been developed for the oxygen- evolution reaction (OER); however, they operate at over potentials significantly above thermodynamic requirements. Density functional theory suggested that non-3d high-valency metals such as tungsten could modulate 3d metal oxides, providing near-optimal adsorption energies for OER intermediates.
The research team examined whether multimetal oxide OER catalysts could be improved by systematically modulating their 3d electronic structure. Prior results suggest that the introduction of additional metals has a limited impact on the behavior of the 3d metals, likely because their undesired separation into two non-interacting metal oxide phases. They also performed DFT+U calculations of the energetics of all intermediates (*OH, *O, *OOH) and extracted over potentials for the set of unary and Fe and W doped surfaces mentioned above (see computational methodology in Supplementary Material).
DFT+U calculated OER activities of pure and W-doped CoFe oxy-hydroxides and W oxides. The optimum is obtained for WFe-doped β-CoOOH. The insets show the optimized structures and location of dopants and active sites at potential limiting step. For DFT+U methodology and detailed information about these systems please refer to Supplementary Material.
Furthermore, the team found that the OER activity of the unary pure CoOOH (01-12) surface can be improved via single-site doping with sub-surface Fe atoms. As theoretically predicted, this improvement can be attributed to a change in ΔGOH and also in ΔGO-ΔGOH at the Co-site, and can be rationalized by the difference in electron affinity between Co4+ (at the surface) and Fe3+ (subsurface) sites. These gelled FeCoW oxy-hydroxide exhibits the lowest over potential reported at 10 mA per square centimeter in alkaline electrolyte.
The OER polarization curve of catalysts loaded on two different substrates with 1 mV s−1 scan rate, without iR-correction: Au (111) electrode and chronopotentiometric curves obtained with the G-FeCoW oxyhydroxides on gold-plated Ni foam electrode with constant current densities of 30 mA cm−2, and the corresponding Faradaic efficiency from gas chromatography measurement of evolved O2.
Professor Jeffrey C. Grossman from MIT and Professor Gabor A. Somorjai from University of Berkeley, California, highly values this research. The achievement obtained a patent in Canada, it also received finically support from the China Scholarship Council and Fonds de recherché du Québec – Nature et technologies (FRQNT). The Nanotech, SLAC, and University of Toronto reported this research team and the achievement.
