Abstract
The hydrogen evolution reaction (HER) as part of water splitting is a fundamental electrocatalytic process and plays a crucial role in hydrogen-based energy conversion. Although platinum and its group metals rank among the most active electrocatalysts for the HER, the slow reaction kinetics under alkaline media conditions has hindered their application in alkaline water electrolyzers. Therefore, much effort has been devoted to exploring highly active electrocatalysts for the alkaline HER. Transition-metal hydroxides/oxides are efficient for the prior water-dissociation step of alkaline HER, and therefore, combining these materials with Pt may be promising candidates for alkaline HER catalysts. Here, we demonstrate that Pt nanoparticles supported on interconnected NiFe oxide particles can serve as enhanced catalysts for alkaline HER.The NiFe oxide was synthesized by the flame pyrolysis method.1,2 The Pt nanoparticles were loaded on the NiFe oxide by a modified colloidal method.3,4 The as-prepared Pt/NiFe oxide sample was reduced in 5% H2 (N2 balance) at 100 oC for 1h. The Pt loading was determined to be 28.3 wt% by inductively coupled plasma-optical emission spectroscopy (ICP-OES). The scanning transmission electron microscopy (STEM) image was shown in Figure 1 ((a) secondary electron (SE) image and (b) transmission electron (TE) image). It can be seen that Pt nanoparticles (some interconnected to form rod/wire-like structures) are dispersed on the NiFe oxide support. Figure 1c shows the HER polarization curves of Pt/NiFe oxide compared with a commercial catalyst Pt/C (TEC10E50E, TKK). The HER specific activity (j s) and mass activity (MA) were summarized in Figure 1d. The HER activity is shown to be greatly enhanced on the Pt/NiFe oxide catalyst, with the specific activity and mass activity (@-0.1 V) being approximately 3.9 and 2.4 times higher than that of Pt/C, respectively. The high mass activity of Pt/NiFe oxide would make it possible to lower the Pt usage, and thus cost, when implemented as a cathode in a practical alkaline water electrolyzer. In addition, the Pt/NiFe oxide catalyst was further heat-treated at high temperatures to obtain different nanostructures and elucidate the structure-activity relationship, achieving optimal HER activity at a moderate hydrogen binding energy. These results are expected to aid in the design of highly efficient HER catalysts for hydrogen production by alkaline water electrolysis. Acknowledgement This work was partially supported by the JSPS KAKENHI (23H02059) and the projects from the New Energy and Industrial Technology Development Organization (NEDO) of Japan. References K. Kakinuma, M. Uchida, T. Kamino, H. Uchida, and M. Watanabe, Electrochim. Acta, 56, 2881 (2011).G. Shi, T. Tano, D. A. Tryk, M. Yamaguchi, A. Iiyama, M. Uchida, K. Iida, C. Arata, S. Watanabe, and K. Kakinuma, ACS Catal., 12, 14209 (2022).G. Shi, T. Tano, D. A. Tryk, A. Iiyama, M. Uchida, and K. Kakinuma, ACS Catal., 11, 5222 (2021).G. Shi, T. Tano, D. A. Tryk, T. Uchiyama, A. Iiyama, M. Uchida, K. Terao, M. Yamaguchi, K. Tamoto, Y. Uchimoto, and K. Kakinuma, ACS Catal., 13, 12299 (2023). Figure 1
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