A chelate to break diffusion limits on Helmholtz plane for CO2 electroreduction to ethanol

The distribution of anions within the Helmholtz plane features a determined effect on the reaction selectivity of CO2 electroreduction reaction (CO2RR). However, the conventional anions diffusion approach from the bulk electrolyte to the electrode-electrolyte interface is hampered by diffusive mass transfer resistance and electrostatic repulsion, resulting in difficulties in fast anions enrichment within the Helmholtz plane. Herein, Cu chelates are systematically screened, and a citrate-coordinated Cu chelate featuring rapid interfacial wettability reversal and minimum reconstruction potential is developed to enrich the citrate anion (CA) in the Helmholtz plane instead of in bulk solution and break the anions diffusion limits to achieve an internal inside to on-surface diffusion beyond the traditional external outside to above-surface diffusion. The enriched CA at the reaction interface is able to modulate the reaction pathway and accelerate C2H5OH electrosynthesis, in which a Faradaic efficiency of 55.3% and partial current density of 297 mA cm−2 for C2H5OH are achieved. This system opens an avenue to refine interfacial microenvironment by designing metal chelates for high-efficiency electrocatalysis. Modulating the microenvironment of the Helmholtz plane, especially the anion transport, is crucial and challenging for CO2 electrocatalytic systems. Here, the authors report a metal chelate to break diffusion limits and enrich the anions in the Helmholtz plane, promoting ethanol electrosynthesis.