Cadmium-based metal-organic frameworks for high-performance electrochemical CO2 reduction to CO over wide potential range

Highly Active and Stable Cu-Cd Bimetallic Oxides for Enhanced Electrochemical CO2 Reduction

Electrochemical reduction of carbon dioxide (CO2) can produce value-added chemicals such as carbon monoxide (CO) and multicarbon (C2+). However, the complex reaction pathways of CO2 electro-reduction reaction (CO2RR) greatly limit the product selectivity and conversion efficiency. Herein, the Cu-Cd bimetallic oxides catalyst was designed and applied for the CO2RR. The optimized 4.73 %Cd-CuO exhibits remarkable electrocatalytic CO2RR activity for selective CO production in H-cell using 0.5 M 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6)/MeCN as electrolyte. The Faradaic efficiency of CO (FE(CO)) can be maintained above 90 % over a wide potential range of -2.0 to -2.4 V vs. Ag/Ag+. Particularly, the catalyst achieves an impressive FE(CO) of 96.3 % with a current density of 60.7 mA cm-2 at -2.2 V vs. Ag/Ag+. Furthermore, scaling up the 4.73 %Cd-CuO catalyst into a flow cell can reach 56.64 % FE of C2+ products (ethylene, ethanol and n-propanol) with a current density as high as 600 mA cm-2 steadily. The excellent CO2RR performance of the as-synthesized 4.73 %Cd-CuO can be mainly attributed to the introduction of CdO to improve the ability of CuO to activate CO2, the electronic interactions between Cu and Cd can boost the activation and conversion the key intermediates of CO2RR and ensure the continuous stability of the 4.73 %Cd-CuO in electrolysis process.

Cd/Cd(OH)2 Nanosheets Enhancing the Electrocatalytic Activity of CO2 Reduction to CO

Electric-driven conversion of carbon dioxide (CO2 ) to carbon monoxide (CO) under mild reaction conditions offers a promising approach to mitigate the greenhouse effect and the energy crisis. Surface engineering is believed to be one of the prospective methods for enhancing the electrocatalytic activity of CO2 reduction. Herein, hydroxyl (OH) groups were successfully introduced to cadmium nanosheets to form cadmium and cadmium hydroxide nanocomposites (i. e. Cd/Cd(OH)2 nanosheets) via a facile two-step method. The as-prepared Cd/Cd(OH)2 /CP (CP indicates carbon paper) electrode displays excellent electrocatalytic activity for CO2 reduction to produce CO. The Faradaic efficiency of CO reaches 98.3 % and the current density achieves 23.8 mA cm-2 at -2.0 V vs. Ag/Ag+ in a CO2 -saturated 30 wt% 1-butyl-3-methylimidazole hexafluorophosphate ([Bmim]PF6 )-65 wt% acetonitrile (CH3 CN)-5 wt% water (H2 O) electrolyte. And the CO partial current density can reach up to 71.6 mA cm-2 with the CO Faradaic efficiency of more than 85 % at -2.3 V vs. Ag/Ag+ , which stands out against Cd/CP, Cd(OH)2 /CP, and Cd/CdO/CP electrodes. The excellent electrocatalytic performance of the Cd/Cd(OH)2 /CP electrode can be attributed to its unique structural properties, suitable OH groups, perfect interaction with electrolyte, abundant active sites and fast electron transfer rate.

Selective electrochemical reduction of CO2 on compositionally variant bimetallic Cu-Zn electrocatalysts derived from scrap brass alloys

The electrocatalytic reduction of carbon dioxide (CO₂RR) into value-added fuels is a promising initiative to overcome the adverse effects of CO₂ on climate change. Most electrocatalysts studied, however, overlook the harmful mining practices used to extract these catalysts in pursuit of achieving high-performance. Repurposing scrap metals to use as alternative electrocatalysts would thus hold high privilege even at the compromise of high performance. In this work, we demonstrated the repurposing of scrap brass alloys with different Zn content for the conversion of CO₂ into carbon monoxide and formate. The scrap alloys were activated towards CO₂RR via simple annealing in air and made more selective towards CO production through galvanic replacement with Ag. Upon galvanic replacement with Ag, the scrap brass-based electrocatalysts showed enhanced current density for CO production with better selectivity towards the formation of CO. The density functional theory (DFT) calculations were used to elucidate the potential mechanism and selectivity of the scrap brass catalysts towards CO₂RR. The d-band center in the different brass samples with different Zn content was elucidated.