Ce-doped CoP nanoparticles embedded in carbon nanotubes as an efficient and durable catalyst for hydrogen evolution

In this work, a cerium doped CoP nanoparticles (NPs) embedded in carbon nanotubes (CNTs) for efficient and durable hydrogen evolution was developed. The detailed preparation process was described as the followings. First, cerium was introduced into ZIF-67 to form Ce-doped ZIF-67 by a joint nucleation method. Then, the Ce-doped Co-CNTs was synthesized by carbonization of Ce-doped ZIF-67. During the process, the Co²⁺ was reduced to form Co NPs and the elegant nanostructure of CNTs was formed by the catalytic effect of Co NPs. Finally, by using Ce-doped Co-CNTs as the precursor, the target catalyst (Ce_0.05-doped CoP CNTs) was obtained through a chemical vapour deposition (CVD) process in the presence of NaH₂PO₂. Results of the transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the target catalyst maintained the original rhombic dodecahedron morphology of ZIF-67 and the CoP NPs were embedded in CNTs and distributed uniformly throughout the catalyst. In electrochemical measurements, the catalyst showed the best performance for HER in 0.5 M H₂SO₄ solution. The onset potential, Tafel slope, electron transfer resistance (R _ct) and double-layer capacitance (C _dl) of the target catalyst was 49 mV, 78 mV dec^-1, 19.2 Ω and 10.5 mF cm^-2, respectively. Meanwhile, the catalyst yielded a current density of 10 mA cm^-2 merely at an overpotential of 146 mV. Furthermore, it maintained 90% of the original current density in a chronoamperometry measurement and showed no obvious decay even after 2000 cycles scans in a long-term durability test.