Twinning Enhances Efficiencies of Metallic Catalysts toward Electrolytic Water Splitting

Twinning is demonstrated to be an effective way of enhancing efficiencies of metallic catalysts toward electrolytic water splitting. Dendritic Cu possessing dense coherent nanotwin (NT) boundaries (NTCu-5nm) is successfully prepared with an organic-assisted electrodeposition at high pulse current densities. NT boundaries significantly improve electrocatalytic efficiencies and stability of NTCu-5nm over nanocrystalline Cu (NCCu), reducing overpotentials at 10 mA cm(-2) for the oxygen evolution reaction (OER) from 378 to 281 mV and from 235 to 88 mV for the hydrogen evolution reaction (HER), with a small chronoamperometric decay of 5% after 100 h continuous overall water splitting at an ultrahigh initial current density of 500 mA cm(-2), largely outperforming the large chronoamperometric decay of 27% for only 1 h operation of the NCCu//NCCu couple. The defective twin boundaries enable formation of active (CuO2-)-O-III at low overpotentials, thus enhancing OER performance. The synergistic geometric and electronic effects induced by the twin boundaries result in shifts in Gibbs free energies of hydrogen adsorption (Delta G(H)) toward the apex of a volcano plot of exchange current density versus Delta G(H), leading to the remarkable improvement in HER activity.

Automated summary

Twin boundaries significantly enhance the performance of copper-based catalysts, reducing overpotentials for electrolytic water splitting and improving stability. The formation of active (CuO2-)-O-III at low overpotentials enhances the efficiency of the oxygen evolution reaction, while geometric and electronic effects induced by the twin boundaries lead to a remarkable improvement in hydrogen evolution reaction activity.