Koh Jinseok, Choi Eunho, Sakaki Kouji, Kim Daeho, Han Seung Min, Kim Sangtae, Cho Eun Seon
Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.
Department of Nuclear Engineering, Hanyang University, Seoul 04763, Republic of Korea.
Nanoscale. 2021 Oct 21;13(40):16942-16951. doi: 10.1039/d1nr04335h.
Decades of research on solute-induced phase transformation of metal hydride systems have shown the possibility to enhance hydrogen storage properties through novel material design such as nanoconfinement engineering. Nevertheless, the fundamentals of mechanical stress effect on confined Pd nanoparticles remain yet to be elucidated due to the difficulty in linking with hydrogen sorption thermodynamics. Here, a thermodynamic tuning of Pd nanocubes associated with hydrogen sorption as a result of encapsulation by reduced graphene oxide (rGO) layers is demonstrated. Pd nanocubes are constrained by rGO to such a degree that the chemical potential and the pressure hysteresis of the system during hydrogen sorption drastically change while showing a size dependence. A thorough thermodynamic analysis elucidates the role of constraints on hydrogen uptake and release; despite the nanoscale regime, the thermodynamic parameters (enthalpy and entropy) during phase transition considerably increase, a phenomenon not seen before in unconstrained Pd nanoparticle systems.
数十年来，关于金属氢化物体系中溶质诱导相变的研究表明，通过纳米限域工程等新型材料设计来提高储氢性能是有可能的。然而，由于难以将其与氢吸附热力学联系起来，机械应力对受限钯纳米颗粒影响的基本原理仍有待阐明。在此，展示了通过还原氧化石墨烯（rGO）层封装实现与氢吸附相关的钯纳米立方体的热力学调谐。钯纳米立方体受到rGO的约束程度使得在氢吸附过程中系统的化学势和压力滞后显著变化，同时呈现出尺寸依赖性。全面的热力学分析阐明了约束对氢吸收和释放的作用；尽管处于纳米尺度范围，但相变过程中的热力学参数（焓和熵）大幅增加，这一现象在无约束的钯纳米颗粒体系中未曾见过。
