Luo Zhaoyan, Zhou Tingyi, Guan Yi, Zhang Lei, Zhang Qianling, He Chuanxin, Sun Xueliang, Ren Xiangzhong
College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, 518060, P. R. China.
Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON, N6A 5B9, Canada.
Small. 2023 Nov;19(48):e2304750. doi: 10.1002/smll.202304750. Epub 2023 Aug 3.
Replacing high-cost and scarce platinum (Pt) with transition metal and nitrogen co-doped carbon (M/N/C, M = Fe, Co, Mn, and so on) catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells has largely been impeded by the unsatisfactory ORR activity of M/N/C due to the low site utilization and inferior intrinsic activity of the M─N active center. Here, these limits are overcome by using a sacrificial bimetallic pyrolysis strategy to synthesize Fe─N─C catalyst by implanting the Cd ions in the backbone of ZIF-8, leading to exposure of inaccessible FeN edge sites (that is, increasing active site density (SD)) and high fast mass transport at the catalyst layer of cathode. As a result, the final obtained Fe(Cd)─N─C catalyst has an active site density of 33.01 µmol g (with 33.01% site utilization) over 5.8 times higher than that of Fe─N─C catalyst. Specially, the optimal catalyst delivers a high ORR performance with a half-wave potential of 0.837 (vs RHE) in a 0.1 m HClO electrolyte, which surpasses most of Fe-based catalysts.
用过渡金属与氮共掺杂的碳（M/N/C，M = 铁、钴、锰等）催化剂替代质子交换膜燃料电池中氧还原反应（ORR）所用的高成本且稀缺的铂（Pt），很大程度上受到了M/N/C的ORR活性不尽人意的阻碍，这是由于M─N活性中心的位点利用率低以及本征活性较差。在此，通过采用牺牲性双金属热解策略，将镉离子植入ZIF-8的骨架中来合成Fe─N─C催化剂，克服了这些限制，从而使难以接近的FeN边缘位点得以暴露（即增加活性位点密度（SD）），并在阴极催化剂层实现了快速的质量传输。结果，最终得到的Fe(Cd)─N─C催化剂的活性位点密度为33.01 µmol g（位点利用率为33.01%），比Fe─N─C催化剂高出5.8倍以上。特别地，在0.1 m HClO电解质中，最佳催化剂具有0.837（相对于可逆氢电极）的半波电位，展现出高ORR性能，超过了大多数铁基催化剂。
