Surface-modified MOFs for synthesizing hollow Fe-CoP polyhedrons encapsulating CoP particles to enhance the performance of OER

Cobalt-based transition metal phosphides (TMPs) exhibit huge potential as efficient OER electrocatalysts for commercial applications. Zeolitic imidazolate framework-67 (ZIF-67) has been served as an appealing precursor for the synthesis of cobalt-based TMPs owing to its distinctive structural advantages. However, the poor conductivity and structural variability of ZIF-67 affect the materials’ OER electrocatalytic performance. To enhance the structural stability and OER performance of ZIF-67 derived TMPs, in this work, a polyhedral TMP nanocomposite with porous hollow structure, featuring Fe-CoP on the outer shell and CoP nanoparticles within the cavity, was synthesized using ZIF-67 as template. The ZIF-67 served as both Co precursor and structure template, and the [Fe(CN) 6 ] 3− served as precursor of Fe dopant and structure stabilizer. The resulting TMP composite electrode (Fe-CoP) effectively retains the framework of ZIF-67, exhibiting prominently improved OER activity (η 10  = 297 mV) and exceptional stability (over 260 h). The Fe–C≡N–Co bonds positively influence the preservation of the sample’s morphology after phosphorization. Additionally, a ligand-substitution strategy is proposed for the formation of the designed structure. This strategy, regulating the morphology of 3D structured MOFs, offers a new understanding on stabilizing the geometric structure of MOFs and their derivatives as structure templates. Graphical abstract