Design and construction of robust nickel-based MOFs for promoting HER catalytic activity

Abstract

The proposal of the dual-carbon target has attracted widespread attention to explore hydrogen evolution reaction (HER) electrocatalysts to promote the development of clean energy. Here, we propose a strategy to form hierarchically porous electrocatalytic hydrogen evolution catalysts (MOFs I−II) by calcining prefabricated Ni-metal–organic frameworks (MOFs 1 − 2) under N2 atmosphere. Among them, three-dimensional (3D) porous MOFs 1 − 2 have been synthesized by solvothermal method based on scissor-shaped tetracarboxylic acid, named {[Ni2(L)(1,3-bit)(H2O)3](C2H3N)}n (MOF 1) and [Ni4(tib)(L)2(H2O)3(μ2-O)]n (MOF 2). Single crystal diffraction analysis shows that MOF 1 is 3,4,7-connected 3-nodes 3D framework composed of two kinds 2D planes, while MOF 2 is 2,4,7-connected 3-nodes 3D supramolecular structure constructed from 1D chains and 2D planes. As expected, SEM and BET analysis show that calcination produced a unique hierarchical micro-mesoporous structure, while the specific surface area increases by 2.3–3.8 times. The optimized MOF II exposes more active sites, accelerates electrolyte ion diffusion, and has lower electron transfer resistance, allowing it to exhibit excellent electrocatalytic HER performance in an alkaline environment. Notably, MOF II has a Tafel slope of 81 mV·dec−1 (10 mA·cm−2) with a lower overpotential (225 mV). Compared with the pristine MOF 2, the performance of MOF II is significantly improved and it can operate stably for a long time. The possible electrocatalytic HER mechanism has been investigated by density functional theory (DFT). The results are expected to provide inspiration for the rational design and development of stable and efficient MOF-based HER electrocatalysts.