Enhancing CO2 reduction with formamide-Ni@TiO2 catalyst.

Formamide condensation with Ni can generate the NC structure, widely recognized as an efficient catalyst for electrocatalytic CO2 reduction reaction (CO2RR). To improve the utilization efficiency of Ni atoms, we introduced metal oxides as substrates to modulate the growth of a formamide-Ni (FA-Ni) condensate. FA-Ni@TiO2 demonstrated 2.8 times higher partial CO current density and Ni turnover frequency than FA-Ni, which were also higher than those of other FA-Ni@metal oxides, including ZrO2, Al2O3, Fe2O3, and ZnO. The improved performance of CO2RR can be attributed to the Ni content exposed on FA-Ni@TiO2 being twice that of the raw FA-Ni condensate. The Fourier transform infrared results suggested that formamide was adsorbed on TiO2 via the -CHO group, exposing -NH2 for potential interaction with Ni. As a result, Ni atoms were predispersed on the TiO2 surface. By contrast, the dispersion of Ni atoms was not enhanced by other metal oxides, such as Al2O3, Fe2O3, and ZnO, owing to the robust acidity of their surface sites. These metal oxides adsorbed formamide via -NH2, leading to the absence of extra -NH2 available for binding to Ni atoms. This study provides new insights into the development of appropriate substrates for single-atom catalysts.