Atomically precise Ni clusters inducing active NiN2 sites with uniform-large vacancies towards efficient CO2-to-CO conversion

CO2 electroreduction to CO promises to give an efficient strategy for CO2 fixation and transformation. However, current reported active sites fail to deliver sufficient activity with high CO Faradic efficiency (FEco) over a wide range of potential. Here, we show a general synthetic protocol to fabricate a batch of highly pure and active NiN2 catalysts with precise engineering of the uniform-large (UL) vacancy around the active sites, which is accomplished through the 'pre-deposition + pyrolysis' of various atomically precise Ni clusters (Nin) and in-situ etching of the support by the 'nano bomb' (sulfur-ligand in the clusters). The NiN2 sites with UL vacancies could achieve a high turnover frequency (TOF) of 350000 h-1 with ~100% FEco in a wide potential range of 1500 mV. In-situ infrared spectra and theoretical calculations reveal that a highly pure NiN2 site with UL vacancy contributes to this remarkable catalytic performance compared to the counterparts. This general synthetic strategy enables us to simultaneously engineer active sites and surrounding vacancies with the employment of atomically precise metal clusters, thereby enhancing catalytic performance for other specific reactions.