Citation: | Pengbo Wang, Yibo Wang, Zhaoping Shi, Hongxiang Wu, Jiahao Yang, Jing Ni, Junjie Ge, Changpeng Liu, Wei Xing. Ruthenium-based metal oxide for acidic oxygen evolution reaction: advances and challenges[J]. Energy Lab, 2023, 1(3): 220018. doi: 10.54227/elab.20220018 |
Utilizing proton exchange membrane water electrolyzers (PEMWE) to produce hydrogen is a promising way to provide clean energy, reduce carbon emissions and improve the utilization rate of renewable energy. The slow kinetics of oxygen evolution reaction (OER) at the anode is considered to be the crucial obstacle to its conversion efficiency. Due to the strong acidic and oxidizing environment of OER reaction, it is essential to develop electrocatalyst with high activity and high stability to reduce the high kinetic barrier of OER and improve the reaction rate. Among them, Ru-based catalysts have outstanding catalytic activity and relatively low price, which has aroused great interest in its practical application. Many Ru-based catalysts with superior performance have been developed in recent years. In this review, we mainly focus on the development of Ru-based catalysts towards OER, with OER mechanisms discussed first, followed by discussion in the factors affecting the catalytic performance, and then introduce current research progress of Ru-based catalysts under acidic conditions. We finally conclude the prospect of the development direction of Ru-based catalysts in the future, hopefully guiding further development of Ru-based catalysts towards real world operation.
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a Simplified schematic of the AEM mechanism. b Simplified schematic of the LOM mechanism. c Simplified schematic of the OPM mechanism.[45] Copyright 2021, Spring Nature. d The mechanism for OER and dissolution on Ru and RuO2 electrodes.[28] Copyright 2022, Elsevier. e Divanis, S et al. proposed a different AEM mechanism diagram from the traditional AEM.[46] Copyright 2021, Royal Society of Chemistry.
a Illustration of the Synthesis of Co-doped RuO2 Nanorods. b Proposed LOM and AEM mechanisms. Thermodynamic, L1 is energetically more favorable than A2. (A1 and L1 represent the first reaction step of AEM mechanism and LOM mechanism respectively) c The charge energy difference of A1 and L1 to illustrate the lower electron depletion on OvI than Ru2, which is attributed to the higher activity of OvI in OER process. d The free energy diagrams of the two mechanisms of LOM and AEM. The rate-determining barriers together with that versus RHE are denoted.[56] Copyright 2020, Elsevier.
a Structures for key intermediates of OPM and AEM reaction pathways. b The free energy (ΔG) diagrams of AEM and OPM at 1.23 V versus RHE. States O1–O9 and A1–A9 present the different elementary states in the OPM and AEM pathways, respectively. States O1 (*2OH) and O2 (* 2OH′) differ in the positions of two OH groups. States O9/A9 are the same as the states O1/A1. TS stands for the transition state. Colours in the figure: green balls are Ru; violet balls are Mn; red balls are O; white balls are H.[45] Copyright 2021, Spring Nature.
Strategies for improving the OER performance of Ru-based catalysts.
a High-resolution spectra of XPS of Mn-RuO2 and Nano RuO2 for Ru 3p. b High-resolution spectra of XPS of Mn-RuO2 for Mn 2p. c Ru K-edge XANES spectra for Mn-RuO2, Ru foil, and commercial RuO2 (inset) the amplifying rising edge of the XANES spectra. d Relation between Ru oxidation state and absorption energy. e OER polarization curves of Mn-RuO2, Nano RuO2 and commercial RuO2. f Cdl values estimated through linear fitting of the scan rate.[71] Copyright 2020, American Chemical Society.
a High Resolution Transmission Electron Microscopy (HR-TEM) images of RuO2-250, and the inset in (a) is the corresponding Selected Area Electron Diffraction (SAED) of RuO2-250. b Electrochemical OER polarization curve. c Linear sweep voltammetry (LSVs) before and after 1000th Cyclic Voltammetry (CV) cycling of different RuO2 samples in 0.5 M H2SO4.[72] Copyright 2021, Elsevier. d Electron localization function analysis mapped for the first atomic layer in D-RuO2/TiO2 slab. e Partial electronic density of states of Ru d orbital in RuO2, RuO2/TiO2 and D-RuO2/TiO2. f Density of states of Ti in TiO2, RuO2/TiO2 and D-RuO2/TiO2. [77] Copyright 2022, Elsevier.
a Schematic diagram of synthesis process of a/c-RuO2. b The polarization curves of a/c-RuO2 and commercial RuO2 in 0.1 M HClO4. c Tafel plots of a/c-RuO2 and commercial RuO2. d Wavelet-Transform Extended X-ray Absorption Fine Structure (WT-EXAFS) spectrum of a/c-RuO2. e Chronopotentiometric measurement results for a/c-RuO2 and commercial RuO2 at 10 mA cm−2 in 0.1 M HClO4. f Calculated negative overpotential (-ηOER) plotted against descriptor of ΔG(O*)-ΔG(*OH) for different catalysts.[83] Copyright 2021, John Wiley and sons.
a High Angle Angular Dark Field-Scanning Transmission Electron Microscopy (HAADF-STEM) image of Ru1–Pt3Cu. b Atomically resolved elemental mapping of Ru1–Pt3Cu. c XANES spectra of Ru1-Pt3Cu. d Fourier Transform- Extended X-ray Absorption Fine Structure (FT–EXAFS) spectra of the Ru K edge.[92] Copyright 2019, Spring Nature. e Rietveld refinement on the Power X-ray Diffraction (PXRD) (Mo-Kα1) data of NaRuO2; the crystal structure of NaRuO2 is also shown in the inset. f Atomic Force Microscope (AFM) image and height profile taken along the white line of the exfoliated nanosheets. g Transmission Electron Microscope (TEM) image and (in inset) the experimental (left) and simulated (right) Selected Area Electron Diffraction (SAED) patterns of a nanosheet along the [001] zone axis.[93] Copyright 2019, John Wiley and sons.
a Partial Density of State (PDOS) of the RuO2 and Li0.52RuO2. b Ex situ X-ray Diffraction (XRD) patterns of the pristine RuO2 and the LixRuO2. c Charge density distribution at the (110) crystal plane of LixRuO2, with n = 0 (left) and 16 (right).[79] Copyright 2022, Spring Nature. d Polarization curves of CaCu3Ru4O12 and the commercial RuO2 measured in O2-saturated 0.5 M H2SO4 solution. e Chronopotentiometric measurements of CaCu3Ru4O12 and the commercial RuO2 at 10 mA cm−2geo. f Calculated free energy diagrams of CaCu3Ru4O12. The optimized structures of HO*, O*, and HOO* adsorptions on the surfaces are shown in the insets.[103] Copyright 2019, Spring Nature.