An air-stable, reusable Ni@Ni(OH)2 nanocatalyst for CO2/bicarbonate hydrogenation to formate

Abstract

Production of formate via CO₂/bicarbonate hydrogenation using cheap metal-based heterogeneous catalysts is attractive. Herein, we report the organometallic synthesis of a foam-like Ni@Ni(OH)₂ composite nanomaterial which exhibited remarkable air stability and over 2 times higher catalytic activity than commercial RANEY® Ni catalyst in formate synthesis. Formate generation was achieved with an optimal rate of 6.0 mmol g_cat⁻¹ h⁻¹ at 100 °C, a significantly lower operation temperature compared to the 200–260 °C reported in the literature. Deep characterization evidenced that this nanomaterial was made of an amorphous Ni(OH)₂ phase covering metallic Ni sites; a core–shell structure which is crucial for the stability of the catalyst. The adsorption of bicarbonates onto the Ni@Ni(OH)₂ catalyst was found to be a kinetically relevant step in the reaction, and the Ni–Ni(OH)₂ interface was found to be beneficial for both CO₂ and H₂ activation thanks to a cooperative effect. Our findings emphasize the underestimated potential of Ni-based catalysts in CO₂ hydrogenation to formate, indicating a viable strategy to develop stable, cheap metal catalysts for greener catalytic applications.