Proton exchange membrane fuel cells (PEMFCs) are operated in a range of different environments including near-dry operating conditions. When a PEMFC operates under low relative humidity (RH) conditions, performance degradation rapidly occurs because of the decreased ionic conductivity of dehydrated membrane electrode assemblies (MEAs). As such, securing additional water inside the MEA is important for achieving a high-performance PEMFC under low RH operating conditions. Herein, amorphous carbon-encapsulated carbon nano-onions (AC-CNOs) were prepared by laser pyrolysis method. The hydrophilicity of AC-CNOs varied on the basis of particle size, which affected the amount of oxygen functional groups attached to the amorphous carbon. To confirm the water retention effect of the AC-CNOs, three different catalysts were incorporated into the MEA of the anode electrode, and a Pt@AC-CNO-3 with an average AC-CNO size of ∼164 nm exhibited a significantly improved performance under low RH condition. Moreover, to achieve a synergetic effect from both the anode and cathode, an additional AC-CNO layer was introduced on the cathode catalyst layer. The dual-side MEA with the hydrophilic catalyst layer at the anode and an additional carbon covering layer at the cathode showed significantly increased performance relative to the reference MEA, i.e., >80.2% under RH44%@90°C conditions.

质子交换膜燃料电池 (PEMFC) 在一系列不同的环境中运行，包括接近干燥的运行条件。当 PEMFC 在低相对湿度 (RH) 条件下运行时，由于脱水膜电极组件 (MEA) 的离子电导率降低，性能会迅速下降。因此，在 MEA 内确保额外的水对于在低 RH 操作条件下实现高性能 PEMFC 很重要。在此，采用激光热解法制备了无定形碳包覆的碳纳米洋葱（AC-CNOs）。AC-CNOs 的亲水性根据粒径而变化，这会影响附着在无定形碳上的氧官能团的数量。为了确认 AC-CNOs 的保水效果，在阳极电极的 MEA 中加入了三种不同的催化剂，平均 AC-CNO 尺寸约为 164 nm 的 Pt@AC-CNO-3 在低 RH 条件下表现出显着改善的性能。此外，为了实现阳极和阴极的协同效应，在阴极催化剂层上引入了额外的 AC-CNO 层。在阳极具有亲水性催化剂层且在阴极具有额外碳覆盖层的双面 MEA 相对于参考 MEA 表现出显着提高的性能，即在 RH44%@90°C 条件下 >80.2%。在阴极催化剂层上引入了额外的 AC-CNO 层。在阳极具有亲水性催化剂层且在阴极具有额外碳覆盖层的双面 MEA 相对于参考 MEA 表现出显着提高的性能，即在 RH44%@90°C 条件下 >80.2%。在阴极催化剂层上引入了额外的 AC-CNO 层。在阳极具有亲水性催化剂层且在阴极具有额外碳覆盖层的双面 MEA 相对于参考 MEA 表现出显着提高的性能，即在 RH44%@90°C 条件下 >80.2%。