Laser-induced annealing of metal–organic frameworks on conductive substrates for electrochemical water splitting

Abstract

The conventional thermal transformation of metal–organic frameworks (MOFs) for electrocatalysis requires high temperature, an inert atmosphere, and long duration that result in severe aggregation of metal particles and non-uniform porous structures. Herein, a precise and inexpensive laser-induced annealing (LIA) strategy, which eliminates particle aggregation and rapidly generates uniform structures with a high exposure of active sites, is introduced to carbonize MOFs on conductive substrates under ambient conditions within a few minutes. By systematically considering 8 substrates and 12 MOFs, a series of LIA-MOF/substrate devices with controllable sizes and good flexibility are successfully obtained. These LIA-MOF/substrate devices can directly serve as working electrodes. Remarkably, LIA-MIL-101(Fe) on nickel foam exhibits an ultralow overpotential of 225 mV at a current density of 50 mA cm−2 and excellent stability over 50 h for facilitating the oxygen evolution reaction, outperforming most recently reported transition-metal-based electrocatalysts and commercial RuO2. Physical characterizations and theoretical calculations evidence that the high activity of LIA-MIL-101(Fe) arises from the favorable adsorption of intermediates at its Ni-doped Fe3O4 overlayer that is formed during the laser treatment. Moreover, the LIA-MOF/substrate devices are assembled for overall water splitting. The proposed LIA strategy demonstrates a cost-effective route for manufacturing scalable energy storage and conversion devices.