Ammonia-Mediated CO₂ Capture and Direct Electroreduction to Formate

Abstract

Direct electrochemical conversion of CO 2 capture solutions (instead of gaseous CO 2 ) to valuable chemicals can circumvent the energy-intensive CO 2 regeneration and pressurization steps, but the performance of such processes is limited by the sluggish release of CO 2 and the use of energy-consuming bipolar membranes (BPMs). Herein, we discovered that an ammonium bicarbonate (NH 4 HCO 3 )-fed electrolyzer outperforms the state-of-the-art KHCO 3 electrolyzers largely because of its favorable thermal decomposition property, which allows for a 3-fold increase in the in situ CO 2 concentration, a maximum 23% increase in formate faradaic efficiency, and a 35% reduction in cell voltage by substituting BPM with an anion exchange membrane (AEM). We then demonstrated an integrated process by combining NH 4 HCO 3 electrolysis with CO 2 capture by on-site generated ammonia from the electroreduction of nitrate, which features a remarkable 99.8% utilization of of CO 2 capturing agent. Such a multipurpose process offers a sustainable route for the simultaneous removal of N wastes and streamlined CO 2 capturing and upgrading.

Weakened d–p orbital hybridization inin situreconstructed Ru/β-Co(OH)2heterointerfaces for accelerated ammonia electrosynthesis from nitrates

“…The obtained ammonia product can be extracted using other technologies (e.g., air stripping, capacitor deionization, and selective membrane filtration). [66][67][68] In this work, we used a coprecipitation method to convert the produced ammonia in the electrolyte into struvite (MgNH 4 PO 4 Á6H 2 O) powder (see ESI † for details), which is a typical slow releasing fertilizer that is widely used in agriculture. The XRD pattern demonstrates the ultrahigh purity of the obtained struvite (Fig.…”

Defect engineering of two-dimensional materials for advanced energy conversion and storage

“…[309][310][311][312] Generally, the CO 2 RR mainly contains three steps: the chemical adsorption of CO 2 on active sites, the electron and/or proton transfer to break C-O bonds and/or form C-H bonds, and the desorption of reduction products. [313][314][315] Among these processes, the second step is a proton-coupled multi-step reaction potentially containing varied electron transfer pathways. Affected by the binding state of intermediates, various reduction products can be synthesized, such as CO, HCOOH, CH 4 , HCHO, CH 3 OH, C 2 H 4 , C 2 H 5 OH, and n-C 3 H 7 OH.…”

Carbonation in Low-Temperature CO2 Electrolyzers: Causes, Consequences, and Solutions

“…These authors obtained an FE of 72% for CO at 50 mA/cm 2 by concentrating alkali cations near the electrode surface and (slightly) elevating the temperature. Liu et al 98 investigated CO 2 electrolysis to formate using reactive ammonia solutions. Ammonia and CO 2 were reacted to form ammonium bicarbonate, which was fed to the electrolyzer to convert in situ generated CO 2 to formate.…”