The CO 2 atmospheric concentration level hit the record at more than 400 ppm and is predicted to keep increasing as the dependence on fossil fuels is inevitable. The CO 2 electrocatalytic conversion becomes an alternative due to its environmental and energy-friendly properties and benign operation condition. Lately, bimetallic materials have drawn significant interest as electrocatalysts due to their distinct properties, which the parents' metal cannot mimic. Herein, the indium−bismuth nanosphere (In 16 Bi 84 NS) was fabricated via the facile liquid-polyol technique. The In 16 Bi 84 NS exhibits exceptional performance for CO 2 reduction to formate, with the faradaic efficiency (FE) approaching ∼100% and a corresponding partial current density of 14.1 mA cm −2 at −0.94 V [vs the reversible hydrogen electrode (RHE)]. Furthermore, the FE could be maintained above 90% in a wide potential window (−0.84 to −1.54 V vs the RHE). This superior performance is attributed to the tuned electronic properties induced by the synergistic interaction between In and Bi, enabling the intermediates to be stably adsorbed on the catalyst surface to generate more formate ions.

The electrochemical CO 2 reduction reaction (CO 2 RR) to form C 2+ products was investigated to obtain high selectivity in liquid CO 2 -fed systems having the limitation of low current density. Over the past decade, flow cells with gas diffusion electrodes (GDEs) have emerged to achieve high current densities close to the industrial-relevance scale by overcoming gas diffusion limitations. However, key parameters of GDE design, including binders, were not sufficiently identified to enhance selectivity and current density for C 2+ products. Nafion, FAA-3, and polypyrrole were used to explore the effects of binder type and content on GDE properties such as porosity (gas permeability), ion conductivity, and electron conductivity for the modulation of the CO 2 RR on the Cu 2 O catalyst. The Cu 2 O GDEs with high binder content showed poor selectivity for C 2+ products because of their low exposure to the catalyst surface and decreased gas permeability. The anion exchange ionomer, FAA-3, showed high selectivity for C 2+ products and electrode stability resulting from the C−C coupling increase and suppression of the hydrogen evolution reaction, which was induced by OH − conductivity. In contrast, the cation exchange ionomer, Nafion, exhibited low electrode stability due to the loss of gas products through the catholyte and due to its excessive wettability.

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Single-atom catalysts (SACs) are being widely developed for the CO2 reduction reaction (CO2RR) because of their remarkable activity and selectivity. However, insufficient CO2RR performance and the poor long-term stability of the SACs remain obstacles to process scale-up. Herein, we explore Ni SACs (Ni-N/NCNT) under practical conditions using a zero-gap CO2 electrolyzer for CO production. We demonstrate that the CO2RR performance of the Ni-N/NCNT results from the suitable Ni–N–C, which enhanced electron transfer and increased CO2 adsorption. Furthermore, we propose a strategy for improving the CO2RR performance and long-term stability by focusing on the membrane electrode assembly (MEA) structure. A maximum Faradaic efficiency of 96.73% (at 2.1 V) and partial current density of 219.49 mA cm–2 (at 2.4 V) for CO production were obtained on the MEA with the Ni-N/NCNT catalyst and the Sustainion (Sust.) membrane. In addition, MEA with Sust. exhibited long-term stability at −100 mA cm–2 for over 60 h.