Heterointerface of all-alkynyl-protected Au₂₈ nanoclusters anchored on NiFe-LDHs boosts oxygen evolution reaction: a case to unravel ligand effect

Ultrasmall Au nanoclusters have been proven to effectively enhance the catalytic performance of NiFe layered double hydroxides (NiFe-LDHs) toward oxygen evolution reaction (OER), yet the surface ligand effect of the Au nanoclusters still remains elusive. Herein, a systematic study is reported to examine the OER performance of NiFe-LDHs supported atom-precise all alkynyl-protected [Au₂₈(^tBuC≡C)₁₇]⁻ nanoclusters (Au₂₈-Alkynyl in short) and thiolate-protected Au₂₈(TBBT)₂₀ (TBBT = 4-tert-butylbenzenethiol) counterparts (Au₂₈-Thiolate in short). The Au₂₈-Alkynyl cluster has characteristic absorbance feature, and its composition is verified by mass spectrometry. It possesses a drastically different structure from the reported mixed ligand protected Au₂₈ nanoclusters. Interestingly, the NiFe-LDHs loaded with Au₂₈-Alkynyl exhibited a superior OER performance than the sample loaded with Au₂₈-Thiolate under the same conditions, evidenced by a smaller overpotential of 205 mV at the current density of 10 mA·cm⁻² and a lower Tafel slope value of 41.0 mV·dec⁻¹ in 1 mol·L⁻¹ KOH. Such excellent performance is attributed to the interfaces created between the NiFe-LDHs and the Au nanoclusters, as density functional theory calculations reveal that more significant charge transfer occurs in Au₂₈-Alkynyl/NiFe-LDHs catalyst, and more importantly, the energy barrier of the potential-determining step in the OER process for Au₂₈-Alkynyl/NiFe-LDHs is much lower than that of Au₂₈-Thiolate/NiFe-LDHs hence favors the electrocatalytic reaction.