The electroreduction of nitrate (NO3−) pollutants to ammonia (NH3) offers an alternative approach for both wastewater treatment and NH3 synthesis. Numerous electrocatalysts have been reported for the electroreduction of NO3− to NH3, but most of them demonstrate poor performance at ultralow NO3− concentrations. In this study, a Cu‐based catalyst for electroreduction of NO3− at ultralow concentrations is developed by encapsulating Cu nanoparticles in a porous carbon framework (Cu@C). At −0.3 V vs reversible hydrogen electrode (RHE), Cu@C achieves Faradaic efficiency for NH3 of 72.0% with 1 × 10−3 m NO3−, which is 3.6 times higher than that of Cu nanoparticles. Notably, at −0.9 V vs RHE, the yield rate of NH3 for Cu@C is 469.5 µg h−1 cm−2, which is the highest value reported for electrocatalysts with 1 × 10−3 m NO3−. An investigation of the mechanism reveals that NO3− can be concentrated owing to the enrichment effect of the porous carbon framework in Cu@C, thereby facilitating the mass transfer of NO3− for efficient electroreduction into NH3 at ultralow concentrations.
Tuning the local confinement of reaction intermediates is of pivotal significance to promote C−C coupling for enhancing the selectivity for multicarbon (C 2+ ) products toward CO 2 electroreduction. Herein, we have gained insights into the confinement effect of local CO concentration for enhanced C−C coupling over core− shell Ag@Cu catalysts by tuning the pore diameters within porous Cu shells. During CO 2 electroreduction, the core−shell Ag@Cu catalysts with an average pore diameter of 4.9 nm within the Cu shells
Mass transfer plays an important role in controlling the surface coverage of reactants and the kinetics of surface reactions, thus significantly adjusting the catalytic performance. Herein, we reported that H 2 O diffusion was modulated by controlling the thicknesses of the carbon black (CB) layer between the gas diffusion electrode (GDE) of Cu and the electrolyte. As a consequence, the product distribution over the GDE of Cu was effectively regulated during CO 2 electroreduction. Interestingly, a volcano-type relationship between the thickness of the CB layer and the faradaic efficiency (FE) for multicarbon (C 2+ ) products was observed over the GDE of Cu. Especially, when the applied total current density was set as 800 mA cm −2 , the FE for the C 2+ products over the GDE of Cu coated by a CB layer with a thickness of 6.6 μm reached 63.2%, which was 2.8 times higher than that (16.8%) over the GDE of Cu without a CB layer.
Electroreduction of CO2 into carbonaceous fuels or industrial chemicals using renewable energy sources is an ideal way to promote global carbon recycling. Thus, it is of great importance to develop highly selective, efficient, and stable catalysts. Herein, we prepared cobalt single atoms (Co SAs) coordinated with phthalocyanine (Co SAs‐Pc). The anchoring of phthalocyanine with Co sites enabled electron transfer from Co sites to CO2 effectively via the π‐conjugated system, resulting in high catalytic performance of CO2 electroreduction into CO. During the process of CO2 electroreduction, the Faradaic efficiency (FE) of Co SAs‐Pc for CO was as high as 94.8 %. Meanwhile, the partial current density of Co SAs‐Pc for CO was −11.3 mA cm−2 at −0.8 V versus the reversible hydrogen electrode (vs RHE), 18.83 and 2.86 times greater than those of Co SAs (−0.60 mA cm−2) and commercial Co phthalocyanine (−3.95 mA cm−2), respectively. In an H‐cell system operating at −0.8 V vs RHE over 10 h, the current density and FE for CO of Co SAs‐Pc dropped by 3.2 % and 2.5 %. A mechanistic study revealed that the promoted catalytic performance of Co SAs‐Pc could be attributed to the accelerated reaction kinetics and facilitated CO2 activation.
The electroreduction of nitrate (NO3−) to valuable ammonia (NH3) is a green and appealing alternative to the Haber‐Bosch process. Nevertheless, this process suffers from low performance for NH3 due to the sluggish multi‐electron/proton‐involved steps. In this work, a CuPd nanoalloy catalyst was developed toward NO3− electroreduction at ambient conditions. By modulating the atomic ratio of Cu to Pd, the hydrogenation steps of NH3 synthesis during NO3− electroreduction can be effectively controlled. At −0.7 V versus reversible hydrogen electrode (vs. RHE), the optimized CuPd electrocatalysts achieved a Faradaic efficiency for NH3 of 95.5 %, which was 1.3 and 1.8 times higher than that of Cu and Pd, respectively. Notably, at −0.9 V vs. RHE, the CuPd electrocatalysts showed a high yield rate of 36.2 mg h−1 cm−2 for NH3 with a corresponding partial current density of −430.6 mA cm−2. Mechanism investigation revealed the enhanced performance originated from the synergistic catalytic cooperation between Cu and Pd sites. The H‐atoms adsorbed on the Pd sites prefer to transfer to adjacent nitrogen intermediates adsorbed on the Cu sites, thereby promoting the hydrogenation of intermediates and the formation of NH3.
The Cover Feature illustrates the catalytic process of CO2 electroreduction over phthalocyanine (Pc) coordinated Co sites. Co sites were firstly linked by oxygen species on carbon black, enabling fast electrons transfer. The anchoring of Pc with Co sites further promoted the catalytic activity of CO2 electroreduction into CO. More information can be found in the Communication by J. Zeng, X. Luo and co‐workers.
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