Room-Temperature Electrochemical Conversion of Metal-Organic Frameworks into Porous Amorphous Metal Sulfides with Tailored Composition and Hydrogen Evolution Activity

The conversion of metal-organic frameworks (MOFs) into inorganic nanomaterials is considered as an attractive means to produce highly efficient electrocatalysts for alternative-energy related applications. Yet, traditionally employed MOF-conversion conditions (e.g., pyrolysis) commonly involve multiple complex high-temperature reaction processes, which often make it challenging to control the composition, pore structure, and active-sites of the MOF-derived catalysts. Herein, a general, simple, room-temperature method is presented for a controlled electrochemical conversion of MOF (EC-MOF) films into porous, amorphous metal sulfides (a-MSx). Detailed X-ray photoelectron spectroscopy analysis and control over independent EC-MOF parameters (e.g., scan-rate and potential window) enable to gain insights on the MOF-conversion mechanisms, and in turn to fine-tune the porosity and composition of the obtained MSx. As a result, a highly active amorphous cobalt sulfide (a-CoSx) electrocatalyst can be designed for hydrogen evolution reaction in neutral pH. Furthermore, the adjustable nature of the EC-MOF method allows to draw conclusions about the correlation between the concentration of catalytically active species (S-2(2-) sites) and the hydrogen evolution properties of the a-CoSx. Given the method's generality and the diversity of available MOF structures, EC-MOF provides a compelling platform for a rational design of a wide variety of active electrocatalytic materials.