Regulating nitrogenous adsorption and desorption on Pd clusters by the acetylene linkages of hydrogen substituted graphdiyne for efficient electrocatalytic ammonia synthesis

Precious metal Pd has the intrinsic superiority in adsorbing N₂ molecule and wrecking the high cleavage barrier of the N≡N bond, however, its over-strong adsorption ability is unfavorable to the desorption of the produced NH₃ during the electrochemical N₂ reduction (NRR), which weighs heavily against the NH₃ productivity. Here we demonstrate that the high electron-density of acetylene linkages of hydrogen substituted graphdiyne can regulate the nitrogen adsorption and NH₃ desorption on the active Pd sites (Pd/HsGDY), resulting in impressive electrocatalytic NRR performance. The optimized Pd/HsGDY features an ultrahigh Faraday efficiency of 44.45% and an NH₃ yield of 115.93 mg g⁻¹ h⁻¹ (or 11.59 µg cm⁻² h⁻¹). Density functional theory calculations reveal that the acetylene linkages in HsGDY can tune the d band center of active Pd atoms by downward shifting it from the Fermi level. This favors the hydrogenation of nitrogen on HsGDY-tuned Pd sites and benefits the desorption of produced NH₃ from the catalyst surface to recover active sites induced by heat dissipation during the exothermic hydrogenation processes, resulting in a selectively facilitated electrosynthesis of NH₃.