Jie Wang,a Jing Liu,*a Boyang Zhang,a Jie Gao,a Guangbo Liu,a Xuejing Cui,a Jinxun Liu,*b Luhua Jiang*a
a College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao, Shandong 266042, China
b Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
Abstract
An active and stable bi-functional catalyst for hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) is highly desirable for the clean energy conversion devices, such as anion exchange membrane fuel cells (AEMFCs) and magnesium (Mg)-sea-water batteries. Herein, DFT analysis predicates that the amine-ligand modulation manipulates the d-band center of ruthenium (Ru) downshift from the Fermi level, resulting in optimized hydrogen and hydroxide bonding energies (HBE, OHBE), and thus lowering the limiting energy of HOR/HER. We elaborately fabricate NH2-ligand modulated Ru nanoclusters (Ru/PEI-XC), taking advantage of the abundant -NH2 groups of polyethylene imine (PEI). The optimal Ru/PEI-XC catalyst exhibits a superior HOR activity of 423.3 A/g metal at an overpotential (ƞ) of 50 mV and a specific exchange current density of 687.1 μA/cmmetal, which is about 1.7 and 3.6 folds of the commercial Pt/C catalyst. Ru/PEI-XC presents overwhelming advantage for the HER in a wide pH range, especially in alkaline electrolyte (ƞ = 13 mV at -10 mA/cm), which is 20 mV lower than Pt/C. Both the potentiostatic and accelerated degradation tests manifest an excellent long-term stability of Ru/PEI-XC in catalyzing HORand HER. Furthermore, Ru/PEI-XC as the anode of an AEMFC delivers a peak power density of 1.4 W/mgPGM, comparable with its Pt/C-based counterpart. A proof-of-concept rechargeable Mg-sea-water battery could also be driven by the Ru/PEI-XC cathode, delivers a maximum discharging power density of 18.9 mW/cm, with low charging voltage and good cycling properties. This study reveals that ligand modulation is an effective strategy to manipulate the d-band center of metals and tune the reactivity, which paves an avenue for designing advanced hydrogen electrocatalysts.
DOI: 10.1039/D1TA06995K
