四川大学《Small》：石墨烯气凝胶微球，用于析氢反应高性能电极

摘要：氢气进化反应（HER）的效率与电催化剂的微观结构和电极的宏观结构密切相关。本文，四川大学夏和生教授、贺丽蓉特聘副研究员等在《Small》期刊发表名为“3D Printing of Graphene Aerogel Microspheres to Archi

1成果简介

氢气进化反应（HER）的效率与电催化剂的微观结构和电极的宏观结构密切相关。本文，四川大学夏和生教授、贺丽蓉特聘副研究员等在《Small》期刊发表名为“3D Printing of Graphene Aerogel Microspheres to Architect High-Performance Electrodes for Hydrogen Evolution Reaction”的论文，研究通过电喷雾、原位交联、冷冻干燥和热解等工艺制备了负载有分散良好的超细镍/钴纳米颗粒催化剂的石墨烯气凝胶微球，然后利用直接油墨写入（DIW）技术打印出氢进化反应电极。所获得的石墨烯基气凝胶微球具有独特的卷心菜状介孔结构，可使反应物随时进入活性位点，优化微球内部的传质和质子扩散。DIW 三维打印实现了对周期性晶格宏观几何形状的有序控制，从而促进了气泡从电极表面的快速演化和释放。制备的三维电极在 10 mA cm-2 时的过电位低至 341 mV，比直接用二维石墨烯三维打印电极降低了 31.5%；塔菲尔斜率低至 119.1 mV dec-1，比直接浇铸气凝胶微球制备的电极低 40%。此外，气凝胶微球三维打印电极还具有良好的 HER 稳定性。这项工作为通过三维打印石墨烯气凝胶微球构建高性能 HER 电极提供了一种很好的方法。

2图文导读

图1、通过直接墨水写入（DIW）技术制作嵌入石墨烯基气凝胶微球的三维打印电极。

图2、The SEM images of the outer morphology (a) and inner structure (b) of GOAMs-2Ni1Co; The dependence of apparent viscosity on shear rate for GOAMs-2Ni1Co/C-CNC ink (c); Storage and loss modulus as a function of shear stress for GOAMs-2Ni1Co/C-CNC ink (d); The fitted rheology results of the ink (e) without and (f) with the addition of C-CNC by utilizing the Herschel–Bulkley (HB) model; The digital photo of 3D printed electrode loaded with GOAMs-2Ni1Co/C-CNC(g); The digital photo (h) and the SEM image of 3D printed electrode surface of GOAMs-2Ni1Co/C-CNC(i).

图3、The linear sweep voltammetry (LSV) curves (a), Tafel plots (b) of rGOAMs-xNiyCo reduced at 800 °C before 1000 CV cycles; The change of η10 and Tafel slope of the rGOAMs-xNiyCo reduced at 800 °C before and after 1000 CV cycles (c); The LSV curves (d) of rGOAMs- xNiyCo reduced at 800 °C and their Tafel plots (e) after 1000 CV cycles; The electrochemical surface area (ECSA) (f) of rGOAMs-xNiyCo reduced at 800 °C; XRD pattern (g), XPS narrow scan and the respective peak fitted results of Co (h) and Ni (i) of rGOAMs- xNiyCo.

图4、The LSV curves (a) and Tafel plots (b) of rGOAMs-2Ni1Co reduced at different temperatures before 1000 CV cycles; The change of η10 and Tafel slope of the rGOAMs-2Ni1Co reduced at different temperatures before and after 1000 CV cycles (c); The LSV curves (d) of rGOAMs-2Ni1Co reduced at different temperatures and their Tafel plots (e) after 1000 CV cycles; The ECSA (f) of rGOAMs-2Ni1Co reduced at different temperatures before 1000 CV cycles; The XRD pattern (g), XPS narrow scan and the peak fitted results of Co (h) and Ni (i) of rGOAMs-2Ni1Co reduced at different temperatures.

图5、The TEM images of 3DP rGOAMs-2Ni1Co at different magnification (a)-(b) and the diameters distribution of Ni/Co NPs (c); The mapping image (d) and elemental overlaying mapping result of Ni and Co (e) and their respective mapping results (f)-(g).

图6、(a) The schematic illustration of the water splitting process of the 3D printed electrode of rGOAMs-2Ni1Co in three-electrode system; The LSV curves (b), Tafel plots (c) and their EIS plots (d) of the 3DP rGOAMs-2Ni1Co, bulk electrode with rGOAMs-2Ni1Co via directly casting marked as casted rGOAMs-2Ni1Co, 3D printed electrode with pulverized bulk graphene oxide aerogel with the same composition of rGOAMs-2Ni1Co marked as 3DP rGO-2Ni1Co, and the 3D printed sample with GO and sodium alginate bulk aerogel without Ni/Co marked as 3DP-rGO; (e) The chronopotentiometry curve of the 3DP rGOAMs-2Ni1Co at a constant current density of 10 mA cm−2; (f) The relative comparison of η10 and Tafel slope of the 3DP rGOAMs-2Ni1Co with the literature reported carbon-based carrier loaded with Ni or Co nanoparticles as HER catalysts. (g) The bubble evolution process on the surface of casted rGOAMs-2Ni1Co and 3DP rGOAMs-2Ni1Co at a current density of 10 mA cm−2; The schematic of the difference of pores distribution between rGOAMs-2Ni1Co (h) and 3DP rGOAMs-2Ni1Co (i).

3小结

通过直接墨水三维打印石墨烯气凝胶微球和镍/钴纳米颗粒，制备出了具有周期性晶格宏观几何形状的 HER 电极。为了获得更好的 HER 性能，对 Ni/Co 的比例和热还原温度进行了优化。通过引入羧基化纤维素纳米晶体，成功实现了气凝胶微球的 DIW 三维打印。气凝胶微球的DIW三维打印电极在10 mA cm-2条件下具有约341 mV的低过电位，与二维石墨烯片组成的三维打印电极相比降低了31.5%；具有119.1 mV dec-1的优异Tafel斜率，比未进行三维打印的直接铸造的三维石墨烯微球电极低≈0.4倍。这种气凝胶微球的分层系统提供了理想的通道，使活性位点和最佳传质成为可能，从而促进了质子在电极内的扩散，而三维打印架构的周期性大孔则有利于电极表面的快速气泡演化和发射。此外，该电极在工作超过 24 小时后仍显示出良好的 HER 稳定性，表明其在实际应用中具有巨大潜力。这项工作从电催化剂进步和结构设计的角度为构建高性能 HER 电极提供了一种简便的方法，将引起能源转换领域的极大关注。

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