The electrochemical carbon dioxide reduction reaction (CO2RR) to produce high value-added fuels provides a sustainable path to alleviate the energy crisis and achieve global carbon neutrality. Liquid products have a higher volumetric energy density compared to gas-phase products, as well as they are easier to store and dispense. In particular, formic acid or formic acid (HCOOH) is widely used as an important raw material in medicine, preservatives, electrolytic metallurgy and leather production.
To date, none of the reported electrocatalysts have failed to meet the commercial requirements for Faraday efficiency (Fe) of more than 90% for CO2RR and long-term operation of at least 100 hours. In addition, in a typical H-type or flow-cell reaction setup, the resulting liquid product is often mixed with a soluble electrolyte, requiring additional energy for the downstream separation process. Therefore, there is an urgent need to develop efficient electrocatalysts and insoluble electrolyte systems to obtain high-purity liquid fuel products.
Recently,Zhou Xiaoyuan, Chongqing UniversityGan LiyongwithHan GuangStrongly coupled AG sn-sno2 nanowires were designed and synthesized by self-template conversion and electrochemical reduction strategies. Thanks to the optimized electronic structure, superior conductivity and abundant reactive sites, the obtained AG sn-SNO2 NSS exhibits excellent CO2RR performance, the current density of the CO2 moiety reaches the ampere level (2000 mA cm-2), and the selectivity for the generation of HCOOH by CO2 electroreduction is close to 90%, which is far better than that of the previously reported catalysts.
At the same time, the catalyst was continuously operated for 200 hours at a current density of 200 mA cm-2 without significant activity decay, showing excellent stability.
In-situ spectroscopy and theoretical calculations show that the coupling effect of Ag nanoparticles induces electron enrichment at the Sn site on the surface of sn-sno2, which promotes the formation of key *OCHO intermediates, reduces the energy barrier of *OCHO to *HCOOH conversion, and promotes the rapid progress of the reaction.
Notably, to address the downstream separation cost, the researchers introduced a porous solid electrolyte (PSE) layer into a membrane electrode assembly reactor (MEA) with AG SN-SN2 NSS as the cathode catalyst, which is capable of continuous operation for 200 hours and reduces CO2 to about 012 M of pure HCOOH solution. In general, this work has important guiding significance for the further development of advanced electrocatalysts and innovative device systems to promote the practical application of CO2 reduction to liquid fuels.
strongly coupled ag/sn–sno2 nanosheets toward co2 electroreduction to pure hcooh solutions at ampere-level current. nano-micro letters, 2023. doi: 10.1007/s40820-023-01264-6