Laser-Induced Annealing of Metal-Organic Frameworks on Conductive Substrates for Electrochemical Water Splitting

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.