Boundary in electrocatalytic hydrogen evolution reaction: From single metal to binary intermetallic compounds

Ti 2 Cu, TiCu and TiCu 4 were synthesized and their electrocatalytic activities for hydrogen evolution reaction (HER) were investigated. The hydrogen overpotential observed at 10 mA/ cm 2 ( η 10 ) followed the order Ti 2 Cu ( η 10  = −215 mV) > TiCu ( η 10  = −182 mV) > TiCu 4 ( η 10  = −170 mV). The hydrogen adsorption energy (∆G Had ) on Cu site of TiCu 4 is exergonic and close to optimal position (i.e. ∆G Had  = 0). A synergistic effect was proposed to account for the excellent HER performance of these Ti Cu binary intermetallics compounds that could replace PGM and achieve Midas touch in the future.