Janus Structure Ir–Ir3Ce@IrO2 Nanocrystals as Excellent Bifunctionality Catalysts for Acidic Overall Water Splitting
Description
Enhancing the catalytic performance of iridium (Ir)-based catalysts for water electrolysis under acidic conditions presents a significant challenge. This difficulty primarily arises from the substantial energy barriers associated with the four-electron-proton coupled oxygen evolution reaction (OER) at the anode and the two-electron transfer hydrogen evolution reaction (HER) at the cathode. This study successfully synthesized a novel type of Ir–Ir3Ce@IrO2 nanoparticles supported on defective carbon materials (DCMs; Ir–Ir3Ce@IrO2/DCMs) using freeze-drying and conversion methods. Notably, the catalyst core features a unique Janus structure comprising metal and alloy components. This catalyst demonstrates exceptional acidic OER activity, overall water-splitting catalytic performance, and high stability. Experimental results indicate that the Ir–Ir3Ce@IrO2/DCMs electrocatalyst delivers ultralow overpotentials of 210 mV at 10 mA cm−2 for OER in 0.5 M H2SO4. Both structural characteristics and theoretical calculations suggest that Ir–Ir3Ce@IrO2/DCMs facilitate charge redistribution owing to various factors, including the alloying of precious metals and rare earth alloys, the Janus, structure, and heterogeneous interfaces. The Ir–Ir3Ce@IrO2/DCMs || Ir–Ir3Ce@IrO2/DCMs electrolyzer can operate in acidic electrolytes for >40 h. This study presents a viable strategy to address the issues of instability and low efficiency associated with Ir-based OER electrocatalysts for acidic overall water splitting.
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Structural Characterization: The phase of the electrocatalyst is identified using X-ray diffraction (XRD) of the German-Bruker D8 Advance with a sweep speed of 10 °/min and a range of 5-90 °. The microstructure of the electrocatalyst was examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) on the German-ZEISS-Sigma HD and Japanese-JEOL-JEM 2100F instruments, respectively. Its Raman scattering spectra were recorded at 523 nm excitation light source using Japanese -Horiba-LABRAM HR Evolution. Use the German-Bruker-EmxPlus for detecting electron paramagnetic resonance spectroscopy (EPR) to test for unpaired electron and carbon defects. N2 adsorption analysis was performed using US-Micromeritics-ASAP 2420 at 77 K, and surface area was calculated using Barrett-Emmett-Teller (BET).X-ray absorption spectroscopy (XAS) at the edges of Ir L3 and Ce L3 was performed on the BL14W1 beamline of the Shanghai Synchrotron Radiation Facility, using Ir foils and IrO2, as well as CeCl3 and CeO2 as reference standards. The analysis of XAS spectra is performed by the ATHENA program. The surface electronic structure of the electrocatalyst was detected using X-ray photoelectron spectroscopy (XPS) on the US ThermoFisher ESCALAB Xi+ instrument, using US-Agilent-Agilent 7700/7800(MS) Test its inductively coupled plasma spectrometry/mass spectrometry (ICP-AES/MS) to analyze the concentration of various elements in the catalyst. The in-situ ATR-SEIRAS measurement was carried out on Bruker 70V Fourier-transform infrared (FTIR) spectrometer. Electrochemical Measurement: Electrochemical characterization of the synthesized electrocatalysts was performed ina standard three-electrode system using the CHI 900D (Chenhua, Shanghai, China) electrochemical workstation. 0.5 M H2SO4 solution is used as an acidic electrolyte. The setup includes saturated Ag/AgCl as a reference electrode, platinum mesh as a counterelectrode, and an electrocatalyst (loaded 0.32 mg cm−2) on carbon paper with Nafion adhesive as a working electrode. The activity and durability of OER and HER were evaluated by linear sweep voltammetry (LSV) at 5 mV s−1, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) at 100 kHz to 0.1 Hz, and potentiometric parameters (CP). The measured potential refers to RHE and corrects the potential loss of the electrolyte resistance with 80% iR-drop compensation. An H-type electrolytic cell was assembled in 0.5 M H2SO4 electrolyte to evaluate the acid water decomposition performance. Dual-function Ir-Ir3Ce@IrO2/DCMs The electrocatalyst (0.32 mg cm−2) supported on carbon paper is used as the anode and cathode of the electrolyzer. For comparison, an electrolytic cell with IrO2 || Pt/C electrode under the same load was prepared. Polarization curves and chronopotentiometry were recorded.