Decouple Intrinsic Activity and Mass Transfer Optimization to Achieve Ultra-High Hydrogen Evolution Reaction Performance at High Current Density
Xuejiang Zhang, Yongsheng Wang, Mengting Chen, Xingdong Wang, Jiajing Pei, Rui Sui, Lipeng Zhang, Yufeng Zhang, Wei Zhu, Zhongbin ZhuangAbstract
Improving the hydrogen evolution reaction (HER) performances of the Pt catalysts is important for reducing the cost of proton exchange membrane water electrolyzers. Understanding the origin of the overpotential when Pt/C catalyzes the HER is significant for designing high-performance HER catalysts. Here, we identify that mass transfer dominates the HER overpotential on Pt/C rather than intrinsic activity. When the Pt/C loading is greater than 50 µgPt cm–2, the HER performance does not increase with further improvement in its intrinsic activity. Mass transfer controls the HER performance, and this limitation can be overcome by using a nanorod array substrate decoupled from HER active sites. Pt nanoparticles supported on a CoP nanorod array (Pt/CoP-NRA) with ultra-low Pt loadings are synthesized and illustrate ultra-high HER performance. At an overpotential of 120 mV, the Pt/CoP-NRA shows a mass activity of 24.4 mA μgPt–1, which is 5.4 times as high as that of Pt/C. The Pt/CoP-NRA exhibits a negligible degradation in a 1000 h chronoamperometric test at the level of 500 mA cm–2. A mechanism study demonstrates that the nanoarray substrates accelerate the detachment of the generated bubbles by reducing the adhesive force and thereby enabling smaller bubbles to be removed from the electrode surface, resulting in enhanced mass transfer.