Abstract
Catalyst coated membrane (CCM) is the core component of proton exchange membrane water electrolyzers (PEMWEs) and confronts the challenge of unaffordable Ir loading of 2–4 mg cm−2, polarization loss and inferior stability closely correlated with low-activity disordered thick catalyst layers (CLs, 3–10 μm) frequently fabricated by catalyst ink painting. We report wet-chemical direct growth of semi-ordered PtIr nanoflowers array as CLs on both sides of membrane, leading to an integrated ultra-low PtIr CCM (IUCCM) with a single-side PtIr loading of 62.7 μg (1.8 μg Pt+60.9 μg Ir) cm−2 and a CL thickness of 429.1 ± 62.9 nm. Remarkably, the IUCCM exhibits 20.8 %, 34.8 % and 23.8 % attenuation of activation, ohmic and mass transfer polarization relative to a house-made CCM, respectively, and a current density of 2 A cm−2 at 1.77 V as well as the highest specific power of 21.5 kW gIr−1 at 1.6 V in the literature. The improvement of activation polarization is primarily arising from the electronic effect between Pt and Ir as evidenced by the d-band center downshift of 0.80 eV. The thin and semi-ordered CL largely accounts for the mitigation of mass transfer and ohmic polarization. Notably, the IUCCM displays a good long-term stability with a degradation rate of ca. 44.4 μV h−1 during 300 h of electrolysis at 0.5 A cm−2. The superior stability can be attributed to strong CL/membrane interfacial interaction with the CL rooted down into the membrane matrix analogous to teeth as well as structural robustness of PtIr CL.
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