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

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