Spatially confined electrochemical conversion of metal-organic frameworks into metal-sulfides and their in situ electrocatalytic investigation via scanning electrochemical microscopy.

There is an on-going search for new earth-abundant electrocatalytic materials, suitable for replacing noble-metals as efficient accelerators of energy-conversion reactions. In this regard, over the last few years, metal-organic framework (MOF)-converted materials have demonstrated promising electrocatalytic properties. Nevertheless, the discovery of new catalytic materials requires development of methods combining high-throughput synthesis and electrochemical-activity screening. To do so, here we couple the synthetical and the analytical virtues of scanning electrochemical microscopy (SECM). Namely, we first utilized an SECM tip electrode to induce spatially confined (μm-scale) electrochemical conversion of cobalt-based ZIF-67 MOFs into patterns of cobalt sulfide with a tuned chemical composition. In turn, the same SECM setup was used to map the H2 evolution activity of the as-formed cobalt sulfide. Hence, the presented method should have great implications for future screening of new electrocatalytic materials for a variety of energy-related applications.