Boosting the direct conversion of NH₄HCO₃ electrolyte to syngas on Ag/Zn zeolitic imidazolate framework derived nitrogen-carbon skeleton

Abstract

The electrochemical reduction of NH₄HCO₃ to syngas can bypass the high energy consumption of high-purity CO₂ release and compression after the ammonia-based CO₂ capture process. This technology has broad prospects in industrial applications and carbon neutrality. A zeolitic imidazolate framework-8 precursor was introduced with different Ag contents via colloid chemical synthesis. This material was carbonized at 1000 °C to obtain AgZn zeolitic imidazolate framework derived nitrogen carbon catalysts, which were used for the first time for boosting the direct conversion of NH₄HCO₃ electrolyte to syngas. The AgZn zeolitic imidazolate framework derived nitrogen carbon catalyst with a Ag/Zn ratio of 0.5:1 achieved the highest CO Faradaic efficiency of 52.0% with a current density of 1.15 mA·cm^–2 at –0.5 V, a H₂/CO ratio of 1–2 (–0.5 to –0.7 V), and a stable catalytic activity of more than 6 h. Its activity is comparable to that of the CO₂-saturated NH₄HCO₃ electrolyte. The highly discrete Ag-N_x and Zn-N_x nodes may have combined catalytic effects in the catalysts synthesized by appropriate Ag doping and sufficient carbonization. These nodes could increase active sites of catalysts, which is conducive to the transport and adsorption of reactant CO₂ and the stability of *COOH intermediate, thus can improve the selectivity and catalytic activity of CO.

Graphical abstract

Keywords

Ag catalyst / zeolitic imidazolate framework / CO₂ electroreduction / ammonium bicarbonate electrolyte / syngas

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Higher Education Press