Rezaee Sharifeh, Shahrokhian Saeed
Department of Chemistry, Sharif University of Technology, Tehran 11155-9516, Iran.
Nanoscale. 2020 Aug 14;12(30):16123-16135. doi: 10.1039/d0nr04616g. Epub 2020 Jul 23.
Over the last few years, substantial efforts have been made to develop earth-abundant bi-functional catalysts for urea oxidation and energy-saving electrolytic hydrogen production due to their low cost and the potential to replace traditional noble-metal-based catalysts. Nevertheless, finding a straightforward and effective route to prepare efficient catalysts with unique structural features and optimal supports still is a big challenge. Among the various candidates, metal-organic framework (MOF)-derived materials show great advantages as new kinds of active non-precious catalysts. On the other hand, the controllable integration of MOFs and carbon-based nanomaterials leads to further enhancement in terms of the stability and electrical conductivity of catalysts. In this communication, we develop an MOF-carbon-based composite to synthesize a transition metal phosphide (TMP) catalyst for the electrocatalytic oxidation of urea. First, poly(pyrrole-co-aniline) (PPCA) hollow nanospheres were fabricated via the in situ emulsion polymerization of a mixture of aniline and pyrrole in the presence of Triton X-100. Then, the simple carbonization treatment of these PPCA hollow spheres led to the carbonized hollow carbon nanospheres (HCNs) with ultrahigh surface areas and uniform nano-morphologies. After that, bimetallic MM'/MOFs (M/M' = Ni, Co) were uniformly grown around the HCNs via a simple hydrothermal reaction (NiCo/MOF@HCNs). During the synthesis process, by adjusting Ni/Co ratios, the MOF morphology can be engineered so that by reducing the Ni/Co ratio, the flower-like structures change into urchin-like structures. Finally, this NiCo/MOF@HCNs precursor with different Ni/Co ratios during the in situ carbonization/phosphorization was chemically converted into Ni-Co mixed-metal phosphides (NiCoP/C@HCNs). Finally, the electrocatalytic activity of the prepared catalysts was tested for the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER).
在过去几年中，人们付出了巨大努力来开发用于尿素氧化和节能电解制氢的地球丰富型双功能催化剂，因为它们成本低且有潜力替代传统的贵金属基催化剂。然而，找到一条直接有效的途径来制备具有独特结构特征和最佳载体的高效催化剂仍然是一个巨大的挑战。在各种候选材料中，金属有机框架（MOF）衍生材料作为新型活性非贵金属催化剂显示出巨大优势。另一方面，MOF与碳基纳米材料的可控整合导致催化剂在稳定性和电导率方面进一步提高。在本通讯中，我们开发了一种MOF-碳基复合材料，以合成用于尿素电催化氧化的过渡金属磷化物（TMP）催化剂。首先，通过在Triton X-100存在下苯胺和吡咯混合物的原位乳液聚合制备了聚（吡咯-共-苯胺）（PPCA）空心纳米球。然后，对这些PPCA空心球进行简单的碳化处理，得到具有超高表面积和均匀纳米形态的碳化空心碳纳米球（HCNs）。之后，通过简单的水热反应在HCNs周围均匀生长双金属MM'/MOFs（M/M' = Ni，Co）（NiCo/MOF@HCNs）。在合成过程中，通过调整Ni/Co比例，可以设计MOF的形态，使得通过降低Ni/Co比例，花状结构转变为海胆状结构。最后，将这种在原位碳化/磷化过程中具有不同Ni/Co比例的NiCo/MOF@HCNs前驱体化学转化为Ni-Co混合金属磷化物（NiCoP/C@HCNs）。最后，测试了所制备催化剂对尿素氧化反应（UOR）和析氢反应（HER）的电催化活性。
