The high cost and limited supply of platinum for Pt-based catalysts in proton exchange membrane fuel cells (PEMFCs) have driven intensive research into the use of non-noble metal catalysts in recent years. As the most promising non-noble metal catalysts for PEMFC oxygen reduction reactions (ORR), metal/N/C class of catalysts has been extensively explored. Earlier efforts (1964–2004) were mainly focused on the exploration of various synthesis routes and the investigation of active site mechanisms. During recent years (2005–2010), great progress in the development of these types of non-noble metal catalysts in real PEMFC environments has been achieved both in terms of catalytic activity and stability. From 2011 to present, several new synthetic approaches have been explored to produce highly dense catalytically active sites decorated within micropores using rationally designed zeolite imidazolate frameworks (ZIFs) and porous organic polymers (POPs). Currently, the most active non-noble metal catalysts are derived using this method and are able to deliver a kinetic volumetric current density of 450 A/cm³ at 0.8 V under fuel cell operating conditions. These results are superior to the US DOE 2020 target of 300 A/cm³. In terms of fuel cell maximum power density, the best non-noble metal catalysts for cathodes can achieve results as high as 0.98 W/cm² and 0.41 W/cm² with feeds of pure O₂ and air respectively. In terms of stability, some non-noble metal catalysts have remained stable for over 1000 h with only minor degradation under PEMFC conditions. Nonetheless, activity and stability still remain major challenges for non-noble metal catalysts when compared to Pt-based ones in PEMFCs. Improvements in the structure of both catalysts and catalyst layers are urgently needed to realize the activity targets established for automobile fuel cell applications as well as the US DOE Hydrogen and Fuel Cell (H&FC) program. In the long term and the sustainable commercialization of fuel cells, replacing Pt-based catalysts with non-noble metal catalysts is, in the present authors' opinion, the most sustainable solution. Therefore, further intensive research into fundamental studies is critical to uncovering the workings of active site mechanisms. Once controllable design and synthesize of non-noble metal catalysts with high active site densities and utilization can be achieved, the goal of cost-effective, non-noble metal catalysts in automobile fuel cells can become reality.

近年来，质子交换膜燃料电池（PEMFC）中基于Pt的催化剂的铂金价格昂贵且供应有限，这促使人们对使用非贵金属催化剂进行了深入研究。作为用于PEMFC氧还原反应（ORR）的最有前途的非贵金属催化剂，金属/ N / C类催化剂已得到广泛研究。早期的工作（1964-2004年）主要集中在探索各种合成途径和研究活性位点机制上。近年来（2005-2010年），在催化活性和稳定性方面，在实际的PEMFC环境中开发这类非贵金属催化剂均取得了巨大进展。从2011年至今，已经探索出几种新的合成方法，以使用合理设计的沸石咪唑酸盐骨架（ZIF）和多孔有机聚合物（POP）在微孔内产生高密度催化活性位点。目前，使用这种方法可以衍生出活性最高的非贵金属催化剂，并且能够提供450 A / cm的动态体积电流密度在燃料电池工作条件下为0.8 V时为³。这些结果优于美国能源部2020年设定的300 A / cm ^3的目标。在燃料电池的最大功率密度而言，对于阴极最好的非贵金属催化剂可以达到的效果高达0.98瓦/厘米²和0.41瓦/厘米²与纯氧的进料₂和空气。就稳定性而言，某些非贵金属催化剂在PEMFC条件下可保持稳定超过1000小时，而降解程度很小。尽管如此，与PEMFC中基于Pt的催化剂相比，活性和稳定性仍然是非贵金属催化剂面临的主要挑战。迫切需要改进催化剂和催化剂层的结构，以实现针对汽车燃料电池应用以及美国DOE氢和燃料电池（H＆FC）计划确立的活性目标。在燃料电池的长期和可持续商业化中，在本作者看来，用非贵金属催化剂替代基于Pt的催化剂是最可持续的解决方案。所以，对基础研究的进一步深入研究对于揭示主动位点机制的工作至关重要。一旦可以实现具有高活性位点密度和利用率的非贵金属催化剂的可控设计和合成，汽车燃料电池中具有成本效益的非贵金属催化剂的目标就可以实现。