Yolk–shell Pd@hollow@C-X (X = 1.5, 3.2, 4.5 and 6) catalysts with Pd as the core and porous carbon as the shell were prepared via the inverse microemulsion method. The carbon shell pore volume and core Pd size were controlled by varying the NH₃·H₂O amount. Results showed that with an increase in the NH₃·H₂O amount, the average particle size of Pd nanoparticles and shell pore volume decreased first and then increased, and when the NH₃·H₂O amount was 3.2 ml, the as-prepared Pd@hollow@C-3.2 catalyst had the smallest Pd particle size and largest shell pore volume as 5.54 ± 1.37 nm and 0.12 m³ g⁻¹, respectively. The smaller Pd particle size can provide more active sites for the adsorption and reaction of H₂ and O₂ reactants, and the larger shell pore volume is beneficial for their adsorption. This makes the Pd@hollow@C-3.2 catalyst possess the highest selectivity and productivity in the H₂O₂ synthesis, reaching 93% and 3197 mmol (g_Pd⁻¹ h⁻¹)⁻¹, respectively, at 1 bar.

中文翻译：

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Pd @ hollow @ CX的碳壳孔体积和核心Pd尺寸对H2O2合成的协同作用

蛋黄-壳钯@中空@ C- X（X = 1.5，3.2，4.5和6）用Pd催化剂为核心和多孔碳作为壳制备经由反相微方法。通过改变NH ₃ ·H ₂ O的量来控制碳壳的孔体积和核的Pd尺寸。结果表明，随着NH ₃ ·H ₂ O量的增加，Pd纳米粒子的平均粒径和壳孔体积先减小后增大，当NH ₃ ·H ₂ O量为3.2 ml时，-制备的Pd @ hollow @ C-3.2催化剂具有最小的Pd粒径和最大的壳孔体积，分别为5.54±1.37 nm和0.12 m ³g ^-1。较小的Pd粒径可为H ₂和O ₂反应物的吸附和反应提供更多的活性位，而较大的壳孔体积对其吸附是有利的。这使得Pd @ hollow @ C-3.2催化剂在H ₂ O ₂合成中具有最高的选择性和生产率，在1 bar下分别达到93％和3197 mmol（g _Pd ^-1 h ^-1）^-1。