Atomically Isolated\nPd Sites Promote Electrochemical\nCO Reduction to Acetate through a Protonation-Regulated Mechanism

Electrochemical CO reduction reaction\n(CORR) offers a\npromising\napproach for sustainable acetate production, the promotion of which\nrequires the control of multiple protonation steps. This paper describes\nthe synthesis of atomically isolated Pd sites onto Cu nanoflakes to\nregulate the protonation of key intermediates. The Pd sites with moderate\nwater activation capability are found to enhance the protonation of\n*CO at the neighboring Cu site to *COH, which is confirmed to be the\nrate-determining step through kinetic isotope effect studies. The\nformation of *COH–*CO is therefore promoted. Additionally,\nthe Pd sites would preferentially protonate the C–OH group\nin *COH–*CO due to the spatial approximability and electronic\nmodulation effects, generating *CCO for the selective formation of\nacetate. An acetate Faradaic efficiency of 59.5% is achieved at −0.78\nV vs reversible hydrogen electrode (RHE), with a maximum partial current\ndensity of 286 mA cm<sup>–2</sup> at −0.86 V vs RHE.\nThe optimized catalyst also exhibits long-term stability for 500 h\nat 100 mA cm<sup>–2</sup> in a membrane electrode assembly.\nThis work reveals a new promoting mechanism for selective CORR with\nsimultaneous tuning of the structural and electronic properties of\nthe proton-supplying sites.