In-Situ-Grown Cu Dendrites Plasmonically Enhance Electrocatalytic Hydrogen Evolution on Facet-Engineered Cu₂O

Herein, facet-engineered Cu2O nanostructures are synthesized by wet chemical methods for electrocatalytic HER, and it is found that the octahedral Cu2O nanostructures with exposed crystal planes of (111) (O-Cu2O) has the best hydrogen evolution performance. Operando Raman spectroscopy and ex-situ characterization techniques showed that Cu2O is reduced during HER, in which Cu dendrites are grown on the surface of the Cu2O nanostructures, resulting in the better HER performance of O-Cu2O after HER (O-Cu2O-A) compared with that of the as-prepared O-Cu2O. Under illumination, the onset potential of O-Cu2O-A is ca. 52 mV positive than that of O-Cu2O, which is induced by the plasmon-activated electrochemical system consisting of Cu2O 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 Cu2O. Ab initio nonadiabatic molecular dynamics (NAMD) simulations revealed the transfer of photogenerated electrons (27 fs) from Cu dendrites to Cu2O nanostructures is faster than electron relaxation (170 fs), enhancing its surface plasmons activity, and the HEI of Cu dendrites increases the charge density of Cu2O. These make the energy level of the catalyst be closer to that of H+/H-2, evidenced by the plasmon-enhanced HER electrocatalytic activity.