Diminishing the usage of Pt without sacrificing its activity still remains a challenge in proton-exchange membrane fuel cells (PEMFCs). Here, we report a gas-promoted dealloying process to prepare a closely packed hybrid electrocatalyst containing Pt-based alloy nanocrystals (NCs) and dense isolated Ni sites. Driven by ammonia and heat, the initial Pt_1.5Ni NC undergoes a dealloying process to form a stable Pt-skin Pt_1.5Ni_1−x alloy due to the continuous detachment of Ni atoms from it. Subsequently, these Ni atoms would be trapped by the adjacent defects on the carbon substrates, resulting in abundant Ni sites distributed closely around the dealloyed Pt_1.5Ni_1−x NC. For a multielectron transferred oxygen reduction reaction (ORR), the hybrid ensures the reduction of the two electrons at Ni single sites, and the corresponding intermediate (OOH*) rapidly migrates to the neighboring Pt-based NC to finish the subsequent electron transfer. This efficient relay catalytic process could greatly reduce the usage of Pt. The resulting catalyst exhibits excellent ORR activity with a mass activity (MA) of 4.10 A mg_Pt⁻¹, exceeding that of commercial Pt/C by a factor of ∼15. More importantly, in practical H₂/O₂ fuel cell tests, a peak power density of 1.72 W cm⁻² and a current density of 0.55 A cm⁻² at 0.80 V can be achieved, both of which exceed DOE 2025 targets.

中文翻译：

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紧密堆积的 Pt1.5Ni1−x/Ni–N–C 杂化物用于氧气还原的接力催化

在不牺牲 Pt 活性的情况下减少 Pt 的使用仍然是质子交换膜燃料电池 (PEMFC) 中的一个挑战。在这里，我们报告了一种气体促进的脱合金工艺，以制备一种包含 Pt 基合金纳米晶体 (NCs) 和致密孤立 Ni 位点的紧密堆积的混合电催化剂。在氨和热的驱动下，初始的 Pt _1.5 Ni NC 经过脱合金过程形成稳定的 Pt 皮 Pt _1.5 Ni _{1− x}合金，这是由于 Ni 原子从其中连续脱离。随后，这些 Ni 原子将被碳基底上的相邻缺陷捕获，导致大量 Ni 位点紧密分布在脱合金 Pt _1.5 Ni _{1− x周围}数控。对于多电子转移氧还原反应 (ORR)，杂化确保了 Ni 单位点的两个电子被还原，相应的中间体 (OOH*) 迅速迁移到邻近的 Pt 基 NC 以完成后续的电子转移。这种高效的中继催化过程可以大大减少铂的使用。所得催化剂表现出优异的 ORR 活性，质量活性 (MA) 为 4.10 A mg _Pt ^-1，超过商业 Pt/C 约 15 倍。更重要的是，在实际的H ₂ /O ₂燃料电池测试中，在0.80 V下可实现1.72 W cm ^-2的峰值功率密度和0.55 A cm ^{-2的电流密度，均超过DOE 2025目标。}