Synthesis of 1T WSe2 on an Oxygen-Containing Substrate Using a Single Precursor

The metallic property of metastable 1T′ WSe2 and its promising catalytic performance have attracted considerable interest. A hot injection method has been used to synthesize 1T′ WSe2 with a three-dimensional morphology; however, this method requires two or more precursors and long-chain ligands, which inhibit the catalytic performance. Here, we demonstrate the synthesis of 1T′ WSe2 on a substrate by a simple heating-up method using a single precursor, tetraethylammonium tetraselenotungstate [(Et4N)2WSe4]. The triethylamine produced after the reaction is an electron donor that yields negatively charged WSe2, which is stabilized by triethylammonium cations as intercalants between layers and induces 1T′ WSe2. The purity of 1T′ WSe2 is higher on oxygen-containing crystalline substrates than amorphous substrates because the strong adhesion between WSe2 and the substrate can produce sufficient triethylammonium (TEA) intercalation. Among the oxygen-containing crystal substrates, the substrate with a lower lattice mismatch with 1T′ WSe2 showed higher 1T′ purity due to the uniform TEA intercalation. Furthermore, 1T′ WSe2 on carbon cloth exhibited a more enhanced catalytic performance in the hydrogen evolution reaction (197 mV at 10 mA/cm2) than has been reported previously.