Highly effective doping in transition metal oxides is critical to fundamentally overcome low carrier conductivity due to small polaron formation and reach their ideal efficiency for energy conversion applications. However, the optimal doping concentration in polaronic oxides such as hematite has been extremely low, for example, less than a percent, which hinders the benefits of doping for practical applications. In this work, we investigate the underlying mechanism of low optimal doping concentration with group IV (Ti, Zr, and Hf) and XIV (Si, Ge, Sn, and Pb) dopants from first-principles calculations. We find that novel dopant-polaron clustering occurs even at very low dopant concentrations and resembles electric multipoles. These multipoles can be very stable at room temperature and are difficult to fully ionize compared to separate dopants, and thus they are detrimental to carrier concentration improvement. This allows us to uncover mysteries of the doping bottleneck in hematite and provide guidance for optimizing doping and carrier conductivity in polaronic oxides toward highly efficient energy conversion applications.
Metal oxides have been attracting extensive interest in the design and engineering of effective electrocatalysts owing to their unique electronic structure and natural abundance. However, the limited electrical conductivity and sluggish electron-transfer kinetics have hampered their widespread applications. These issues can be mitigated by structural engineering with the incorporation of select precious metal species. Herein, iron oxide nanostructures decorated with platinum species are prepared by the facile thermal annealing of a MIL-101 precursor along with the addition of a controlled amount of PtCl4 and exhibit apparent electrocatalytic activity toward the hydrogen evolution reaction in 0.5 M H2SO4. The best sample needs only an ultralow overpotential of −15 mV to reach the current density of 10 mA cm–2, along with a low Tafel slope of 25.4 mV dec–1, a performance markedly better than that of commercial 20 wt % Pt/C. This is ascribed to the synergistic interactions between the Pt and Fe2O3 scaffold that impact the material’s electrical conductivity and electron-transfer kinetics and the Cl residuals that regulate the adsorption free energy of H, as confirmed in computational studies based on density functional theory. Results from this study highlight the unique potential of metal oxide-based nanocomposites as high-performance, low-cost electrocatalysts for electrochemical energy technologies where the performance can be further regulated by anion residuals.
Hematite (α-Fe2O3) is a promising transition metal oxide for various energy conversion and storage applications due to advantages of low cost, high abundance, and good chemical stability. However, its low...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.