Surfactant-Assisted Phase-Selective Synthesis of New Cobalt MOFs and Their Efficient Electrocatalytic Hydrogen Evolution Reaction

Xianhui Bu, Ya-Pan Wu, Wei Zhou, Jun Zhao, Wen-Wen Dong, Ya-Qian Lan, Dong-Sheng Li, Chenghua Sun

Reported here are two new polymorphic Co-MOFs (CTGU-5 and -6) that can be selectively crystallized into the pure 2D or 3D net using an anionic or neutral surfactant, respectively. Each polymorph contains a H2O molecule, but differs dramatically in its bonding to the framework, which in turn affects the crystal structure and electrocatalytic performance for hydrogen evolution reaction (HER). Both experimental and computational studies find that 2D CTGU-5 with the coordinate water and more open access to the cobalt site possesses higher electrocatalytic activity than CTGU-6 with the lattice water. Remarkably, the integration with co-catalysts such as acetylene black (AB) leads to a composite material, AB&CTGU-5 (1:4) with extraordinarily efficient HER catalytic properties among reported MOFs. It exhibits superior HER properties including a very positive onset potential of 18mV, low Tafel slope of 45mV·dec-1, higher exchange current density of 8.6×10-4A·cm-2, and long-term stability.