Meeting the growing global energy demand in a sustainable and environmentally responsible way is a major challenge of our time. Although the use of fossil fuels has greatly promoted the development and progress of mankind, it has also caused serious environmental pollution and global warming, led by large carbon dioxide emissions.
Converting CO2 into chemical products and fuels with high added value is a promising way to solve the problems of environmental pollution and energy shortages. Nowadays, the discovery and development of catalysts and the influence of electrolytes and electrolytic additives on catalytic performance are major topics.
There are three main types of reported CO2 reduction reaction (CO2RR) electrocatalysts: the first type of catalyst uses formate as the main product, such as HG, PB, SN, IN, etc.;The second type of catalyst mainly produces CO, such as AU, AG, CO, ZN, etc.;The last class of catalysts (copper and its derivatives) has proven to be special CO2RR catalysts, which can generate large amounts of alcohols and hydrocarbons.
It is generally accepted that the key to obtaining different products lies in the interaction between the intermediate and the catalyst. Based on this,Wang Gongwei, Zhuang Linhe, Wuhan UniversityLi Zhen of Shantou University (Gonggong Communication) et alNXC shells are coated on the surface of AG nanoparticles (NPS) (core-shell structure, ag@nxc) to promote the formation of CH4 and CH2CH2.
To determine the role of the NXC shell in the CO2RR process, the AG NPS, ag@nxc-1, ag@nxc-2 and ag@nxc-3 catalysts were tested. The adsorption desorption of CO2 on the ag NPS and ag@nxc catalysts was significantly different (at 273 K).
The adsorption capacity of CO2 is much higher than that of pure AG NPS after coating the NXC shell at the same pressure, and the CO2 desorption curve indicates that the pressure required for desorption is much lower than that of adsorption. The large adsorption capacity and the pressure hysteresis during desorption indicate a strong interaction between the adsorbate and the adsorbent. That is, due to the interaction of CO2 and N in the NXC shell, CO2 molecules can be selectively adsorbed by the NXC shell for aggregation.
ag@nxc the difference in the adsorption capacity of the catalyst is related to the thickness of the NXC shell, in order to find out the reason for the enhancement of HER after coating the NXC shell on the surface of AG NPS, the effect of the NXC shell on the HER kinetics under nitrogen atmosphere was studied by using the Tafel slope. For Tafel slope: AG NPS > ag@nxc-1 > ag@nxc-2 ag@nxc-3, from 437 to 344 mV DEC-1.
This indicates that the NXC shell enhances HER dynamics within a certain thickness range. This is consistent with previous reports that the presence of N can activate H2O to promote HER performance, while the Tafel slope of HER on the ag@nxc-3 catalyst increases from 346 to 423 mV DEC-1 at higher application potentials.
It can be inferred that this is due to the fact that the thicker NXC shell slows down mass transfer. These results further confirm the above hypothesis that the NXC shell can activate CO2 and H2O molecules to promote the formation of hydrocarbon products.
The NXC shell is evenly distributed on the surface of the AG nucleus with a thickness of about 21 ~ 7.8 nm。After modifying the NXC shell, the performance of hydrocarbon generation was significantly improved, and the Faraday efficiency of CH4 and CH2CH2 on the optimized ag@nxc catalyst reached 43., respectively8 and 84% or more.
Experiments show that this improvement in performance is not related to the change of the electronic properties of AG NPS, but to the synergistic effect of NXC shell and AG NPS core layer. The multifunctional nature of NXC shells in the CO2RR process has been confirmed by attenuated total reflective surface-enhanced infrared absorption spectroscopy.
Firstly, the residence time of CO intermediates can be prolonged, the desorption process can be slowed down, and C-C coupling can be promotedSecond, it can also activate H2O molecules through the interaction of H2O with the NXC shell. Compared with Ag NPS, the H2O adsorption intensity on the ag@nxc catalyst was significantly increased, with a peak blue shift of about 30 cm-1, indicating that the stronger interaction could activate H2O and provide sufficient adsorption H for further reduction of carbonaceous intermediates.
This work provides a strategy for the conversion of CO2 into hydrocarbon products on non-Cu-based catalysts.
amorphous nxc coating promotes electrochemical co2 deep reduction to hydrocarbons over ag nanocatalysts,acs catalysis, doi: 10.1021/acscatal.2c04580.