CuZnAl-Oxide Nanopyramidal Mesoporous Materials for the Electrocatalytic CO2 Reduction to Syngas: Tuning of H2/CO Ratio

Abstract

Inspired by the knowledge of the thermocatalytic CO2 reduction process, novel nanocrystalline CuZnAl-oxide based catalysts with pyramidal mesoporous structures are here proposed for the CO2 electrochemical reduction under ambient conditions. The XPS analyses revealed that the co-presence of ZnO and Al2O3 into the Cu-based catalyst stabilize the CuO crystalline structure and introduce basic sites on the ternary as-synthesized catalyst. In contrast, the as-prepared CuZn- and Cu-based materials contain a higher amount of superficial Cu0 and Cu1+ species. The CuZnAl-catalyst exhibited enhanced catalytic performance for the CO and H2 production, reaching a Faradaic efficiency (FE) towards syngas of almost 95% at −0.89 V vs. RHE and a remarkable current density of up to 90 mA cm−2 for the CO2 reduction at −2.4 V vs. RHE. The physico-chemical characterizations confirmed that the pyramidal mesoporous structure of this material, which is constituted by a high pore volume and small CuO crystals, plays a fundamental role in its low diffusional mass-transfer resistance. The CO-productivity on the CuZnAl-catalyst increased at more negative applied potentials, leading to the production of syngas with a tunable H2/CO ratio (from 2 to 7), depending on the applied potential. These results pave the way to substitute state-of-the-art noble metals (e.g., Ag, Au) with this abundant and cost-effective catalyst to produce syngas. Moreover, the post-reaction analyses demonstrated the stabilization of Cu2O species, avoiding its complete reduction to Cu0 under the CO2 electroreduction conditions.

Evaluating the efficacy of nanosized CuZnAl and CuZnZr mixed oxides for electrocatalytic CO2 reduction

“…The literature reports clearly indicate that copper-based catalysts with different sizes produce different products. 53 The hydrocarbons and oxygenates were the main products with Cu nanoparticles larger than 15 nm, whereas CO and H 2 were the major products when small-size Cu particles (<3–6 nm) were used as catalysts. The electrocatalytic performance of the synthesized catalysts was affected by the size of CuO and ZnO crystallites, as the nanosized Cu-based catalysts showed better performance compared to the catalysts, which contained large-size Cu clusters (Table S4†).…”

“…The electrocatalytic performance of the synthesized catalysts was affected by the size of CuO and ZnO crystallites, as the nanosized Cu-based catalysts showed better performance compared to the catalysts, which contained large-size Cu clusters (Table S4†). The nanosized CuZn-based catalysts exhibited a pronounced increase in the mesoporous nature, metallic surface area, active site dispersion, and selectivity, 46,53 which contribute to the superior electrocatalytic activity. In the present study, the difference in the CuO and ZnO crystallite size of the as-synthesized catalysts (Table S2†) could explain the electrocatalytic activity and different selectivity of the synthesized catalysts.…”

“…size Cu clusters (Table S4 †). The nanosized CuZn-based catalysts exhibited a pronounced increase in the mesoporous nature, metallic surface area, active site dispersion, and selectivity, 46,53 which contribute to the superior electrocatalytic activity. In the present study, the difference in the CuO and ZnO crystallite size of the as-synthesized catalysts (Table S2 †) could explain the electrocatalytic activity and different selectivity of the synthesized catalysts.…”

H 2 -rich syngas production by sorption enhanced steam gasification of palm empty fruit bunch

“…When CaO was not added, the H 2 /CO ratio was only 2.41 but then increased to 7.45 with the maximum addition of CaO. According to Guzman et al [60], syngas with H 2 /CO ratio > 2 are suitable for fuel, Fischer-Tropsch synthesis, and methanol. Figure 7 shows that CO 2 absorption by CaO increased significantly as Ca/C increased from 0.5 to 1 and continued to increase at a consistent pace when Ca/C grew from 1.5 to 2.…”

Structures, Electronic Properties, and Gas Permeability of 3D Pillared Silicon Carbide Nanostructures

“…In recent years, air pollution has become a serious public health concern in many countries around the world. Reduction and utilization of emitted gases/volatile organic compounds (VOCs) have had an increasing interest to prevent and solve the worst impacts on the natural environment, including global warming, climate change, and human health effects [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. One of the important keys to high efficient gas reduction and utilization is to capture or separate a target gas molecule from gas/VOCs mixtures such as separation of N 2 in ammonia plants [ 21 , 22 ], CO 2 separation in coal-fired power plants [ 23 , 24 ], removal of VOCs from O 2 /N 2 streams [ 25 ], or separation of toxic chemicals from H 2 O [ 26 , 27 ].…”