Synergistic Electrocatalytic Syngas Production from Carbon Dioxide by Bi‐Metallic Atomically Dispersed Catalysts

Abstract

The production of syngas by traditional processes such as steam methane reforming is energetically intensive and produces a large amount of CO2 emissions. In contrast, the electrochemical CO2 reduction reaction (CO2RR) enables the carbon neutral production of syngas at ambient conditions. Among non‐precious metal catalysts, metal‐nitrogen‐carbon electrocatalysts are inexpensive and highly selective towards syngas production. This study examined the selectivity of mono‐ and bi‐metallic (M−N−C, M=Fe, Mo or FeMo) electrocatalysts towards syngas production. The ratio of the CO : H2 in the syngas was tuned by modifying the ratio of the metallic precursors in the bi‐metallic FeMo−N−C catalysts, tailoring the catalysts’ selectivity towards the CO2RR or the hydrogen evolution reaction (HER). The catalyst synthesis temperature(s) were considered as they influence the catalyst morphology and activity. Further, the dependence of the ratio of CO : H2 in the syngas as a function of the potential was explored for the different bi‐metallic catalysts. This work showed that by tailoring both the ratio of Fe : Mo in the bi‐metallic catalyst and optimizing the reductive potential, a CO : H2 ratio between 0.25 to 5 was achievable. This study demonstrated a novel approach in which the ratio of the product syngas composition could be tailored in a single reaction, without the need for further downstream processing to reach a desired composition.

Electrochemical trends of a hybrid platinum and metal–nitrogen–carbon catalyst library for the oxygen reduction reaction

“…[24][25][26] The SSM has been regularly practiced for first row transition metals and utilized for the ORR, carbon dioxide reduction, and reduction of nitrogen species. 27,28 Recently, we extended the SSM to include 4d, 5d and f-metals and synthesized a set of 13 M-N-C catalysts (M = Cr, Mn, Fe, Co, Ni, Cu, Mo, Ru, Rh, Pd, La, Ce and W) for the reduction of nitrogen oxides. 29 Here, we have utilized this set of M-N-C's, and introduced a Pt-N-C sample, comprising a library of 14 M-N-C materials and a metal free N-C catalyst.…”

Atomically Dispersed Metal–Nitrogen–Carbon Catalysts for Electrochemical Nitrogen Transformations to Ammonia and Beyond

“…Atomically dispersed metal–nitrogen–carbon (M–N–C) catalysts have been widely explored and reported for the past several decades, beginning with macrocycles in the 1960s , and first gaining attention as potential platinum group metal (PGM) free catalysts for the oxygen reduction reaction (ORR) in fuel cells. − Aimed at reducing the required metal loading due to the significantly enhanced utilization of atomically dispersed metals compared to their nanoparticle counter parts, where even 2–3 nm particles utilize less than 50% of the atoms, buried under the surface . With extensive research efforts, the tailorability of atomically dispersed catalysts, where the metal center and coordinating ligands can be optimized, the use of M–N–C catalysts has extended to the electrochemical CO 2 reduction reaction (CO 2 RR), N 2 RR, NO 3 /NO 2 RR, and even C–N bond formation. ,− Further research efforts have employed the use of multimetallic sites in a single bi- or trimetallic M–N–C, to selectively target reactant molecules or create cascade catalysis pathways for efficient electrochemical transformations. − A main disadvantage of M–N–C catalysts in N-transformation reactions arises due to the limiting weight percent of metal (usually sub 5 wt %) that can be utilized before nanoclusters or particles are formed, which can limit the total quantity of active sites available, often limiting reaction current densities. Recently, the applicability of M–N–C materials have been extended beyond a primary catalyst, but employed as an active support, where metallic nanoparticles are reduced onto an M–N–C, creating a hybrid nanoparticle/M–N–C catalyst. − The atomically dispersed M–N x sites not only add to the plurality of active sites increasing performance but also electronically alter the state of the nanoparticles, tailoring intermediate adsorption energies and increasing nanoparticle stability.…”

Elucidating electrochemical nitrate and nitrite reduction over atomically-dispersed transition metal sites

“…Atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts have been extensively studied in neighboring electrocatalytic reactions (carbon dioxide reduction-CO 2 RR 27 – 29 , oxygen reduction-ORR 30 , 31 ), demonstrating excellent catalytic activities and unique reaction pathways. Recently, atomically dispersed Fe-N-C catalysts were shown to be very selective for the NO 3 RR to NH 3 32 , 33 , owing to their maximized atomic utilization and favorable NO 3 − adsorption over H + .…”