Promoting ZIF-8-Derived Fe–N–C Oxygen Reduction Catalysts via Zr Doping in Proton Exchange Membrane Fuel Cells: Durability and Activity Enhancements
Promoting ZIF-8-Derived Fe–N–C Oxygen Reduction Catalysts via Zr Doping in Proton Exchange Membrane Fuel Cells: Durability and Activity Enhancements
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DOI：
10.1021/acscatal.2c06118
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发表时间：
2023-03
期刊：
影响因子：
12.9
通讯作者：
Bin Chi;Longhai Zhang;Xiaoxuan Yang;Yachao Zeng;Yijie Deng;Mingrui Liu;Junlang Huo;Chaozhong Li-Chaozhong
中科院分区：
文献类型：
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作者：
Bin Chi;Longhai Zhang;Xiaoxuan Yang;Yachao Zeng;Yijie Deng;Mingrui Liu;Junlang Huo;Chaozhong Li-Chaozhong
原子分散的铁位点和氮共掺杂碳催化剂（Fe-N-C）在质子交换膜燃料电池酸中替代 Pt 进行氧还原反应（ORR）方面表现出良好的性能。然而，Fe-N-C催化剂的耐久性不足严重阻碍了其实际应用。在此，我们报告将 Zr 和 Fe 双金属位点共掺杂到 ZIF-8 衍生的介孔碳中，显着提高了 ORR 的耐用性。特别是，ORR阴极催化剂的膜电极组件在恒定电流密度下连续运行20小时后仅损失25%的电压。经过长达100小时的长时间测试，Zr掺杂的Fe-N-C催化剂保留了40%的初始性能，优于未掺杂Zr的催化剂，仅20小时后活性损失超过70%。阴极还表现出显着改善的 ORR 活性，在氢气/空气条件下实现了 0.72 W cm-2 的最大功率密度。大量的实验表征和密度泛函理论计算表明，催化活性和稳定性的提高是由于Zr基活性位点的形成，其耐酸性比单个Fe位点更强。此外，Zr的掺杂可以抑制H2O2和其他自由基的形成，从而减轻活性位点的退化。可能的 Fe/Zr 双金属活性位点，即 N2(N)-Fe-N2-Zr-N2(O2)，相对于传统的 FeNx 位点，可能具有增强的内在 ORR 活性。
The atomically dispersed iron site and nitrogen co-doped carbon catalysts (Fe–N–C) have demonstrated promising performance in replacing Pt toward the oxygen reduction reaction (ORR) in acids for proton exchange membrane fuel cells. However, the insufficient durability of Fe–N–C catalysts prohibitively hinders their practical applications. Herein, we report that the co-doping of Zr and Fe dual metal sites into a ZIF-8-derived mesoporous carbon exhibited significantly improved durability for the ORR. Especially, a membrane electrode assembly from the ORR cathode catalyst only lost 25% voltage after 20 h of continuous operation at a constant current density. After an extended test of up to 100 h, the Zr-doped Fe–N–C catalyst retained 40% of its initial performance, superior to the catalyst without Zr doping with more than 70% activity loss after only 20 h. The cathode also showed significantly improved ORR activity, achieving a maximum power density of 0.72 W cm–2under H2/air conditions. Extensive experimental characterization and density functional theory calculations suggested that the promoted catalytic activity and stability are due to the formation of Zr-based active sites with enhanced acidic tolerance than the individual Fe sites. Also, the doping of Zr could suppress the formation of H2O2and other free radicals, thus mitigating active site degradation. The possible Fe/Zr dual-metal active sites, i.e., N2(N)–Fe–N2–Zr–N2(O2), likely have enhanced intrinsic ORR activity relative to conventional FeNxsites.