Enabling technologies for the continuous electrically driven conversion of CO₂ and water to multi-carbon products at high current densities

Abstract

We report a soft-templating method for the synthesis of high surface area nickel phosphide catalyst (Ni2P). Ni2P exhibits a 40–50% CO2 reduction products selectivity over H2 formation at current densities ranging from 50–300 mA cm−2 in a flow cell.

Remodelling the chlor-alkali electrolysis process to co-generate useful reduction products from CO2

“…It produces a sponge-like morphology consisting of porous sheets several microns in dimension and with holes of diameter ranging from 50 to 200 nm distributed uniformly with no obvious aggregation. The surface/volume ratio of Ni 2 P prepared by this method 40 is approximately 260-fold greater than that obtained using the high temperature solid-state synthesis method. 21 Powder X-ray diffraction measurements (Fig.…”

“…To understand why these products form, consider that five nickel phosphide binary compounds (Ni x P y ) all convert CO 2 into the same C 1 , C 3 and C 4 products by an identical mechanism that is distinct from copper-based catalysts. Calvinho et al 21 proposed an 11-step mechanism that has been supported by additional experimental 20,40 and computational 20,51 evidence. The potential determining step is CO 2 insertion into a surface hydride bond to form an adsorbed formate species, *HCOO − .…”

“…At 0.8 mA cm −2 the maximum selectivity is for methylglyoxal at 78%, with 2,3-furandiol being the second major product, in agreement with a prior report using an identical catalyst and surface area. 40 Although formic acid is produced at all potentials, its faradaic efficiency never exceeds 5% for any of the three currents. Table 1 (ref.…”

“…Dhiman et al reported electrosynthesis of methylglyoxal at a faradaic efficiency up to 47% at a total current density ranging from 50 to 300 mA cm −2 using a single-phase Ni 2 P catalyst prepared with ultra-high surface area morphology and applied to a gas diffusion electrode. 40 These design criteria and use of a flow cell eliminated the fall-off of CO 2 RR yield to H 2 even at this higher current density. Here, we use their performance data to determine the initial techno-economic feasibility (TEF) of an integrated system combining electroreduction of CO 2 to methylglyoxal (at 50% FE) and chloride oxidation to Cl 2 (at 100% FE).…”

“…We adopted a detergent templating procedure to increase the surface area of the Ni 2 P catalyst compared to the standard solid-state synthesis. 40 First, cetyltrimethylammonium bromide (CTAB) and sodium mono-dodecyl phosphate were stirred (700 rpm) in 200 mL solution of water and cyclohexane (ratio: 1 : 1) for 15 min at room temperature. Then 10 mL 1-hexanol was added to the mixture dropwise and the mixture was further stirred for 30 min.…”