In-Situ-Grown Cu Dendrites Plasmonically Enhance Electrocatalytic Hydrogen Evolution on Facet-Engineered Cu₂ O

Herein, facet-engineered Cu₂ O nanostructures are synthesized by wet chemical methods for electrocatalytic HER, and it is found that the octahedral Cu₂ O nanostructures with exposed crystal planes of (111) (O-Cu₂ O) has the best hydrogen evolution performance. Operando Raman spectroscopy and ex-situ characterization techniques showed that Cu₂ O is reduced during HER, in which Cu dendrites are grown on the surface of the Cu₂ O nanostructures, resulting in the better HER performance of O-Cu₂ O after HER (O-Cu₂ O-A) compared with that of the as-prepared O-Cu₂ O. Under illumination, the onset potential of O-Cu₂ O-A is ca. 52 mV positive than that of O-Cu₂ O, which is induced by the plasmon-activated electrochemical system consisting of Cu₂ O and the in-situ generated Cu dendrites. Incident photon-to-current efficiency (IPCE) measurements and the simulated UV-Vis spectrum demonstrate the hot electron injection (HEI) from Cu dendrites to Cu₂ O. Ab initio nonadiabatic molecular dynamics (NAMD) simulations revealed the transfer of photogenerated electrons (27 fs) from Cu dendrites to Cu₂ O nanostructures is faster than electron relaxation (170 fs), enhancing its surface plasmons activity, and the HEI of Cu dendrites increases the charge density of Cu₂ O. These make the energy level of the catalyst be closer to that of H⁺ /H₂ , evidenced by the plasmon-enhanced HER electrocatalytic activity.