Microstructure Induced Thermodynamic and Kinetic Modulation to Enhance CO₂ Photothermal Reduction: A Case of Atomic-Scale Dispersed Co–N Species Anchored Co@C Hybrid

Abstract

The transformation of CO 2 into a single product is a critical scientific challenge because of the difficulty associated with targeted activation and conversion of CO 2 by heterogeneous catalysts. Herein, we present an atomic-scale dispersed Co−N species anchored Co@C hybrid structure (entitled as Co@ CoN&C) that regulates catalytic properties in thermodynamic and kinetic processes to achieve active and highly selective CO yield in the photothermal CO 2 reduction. An optimal sample delivers the maximum yield rate of 132 mmol g cat.−1 h −1 and remarkable CO selectivity (91.1%), while the undesirable methanation activity, compared with typical Co nanoparticles (NPs), was suppressed. The mechanism study suggests that the strong photon−matter interaction over graphitic-carbon and Co NPs can enhance the light-to-heat conversion efficiency and thus induce the high work temperature, which is thermodynamically beneficial for CO 2 activation and subsequently promoted the catalytic activity. Furthermore, the carbon layers improve the adsorption of CO 2 , and the surface atomically dispersed Co−N species weakens hydrogenation capability, which kinetically controls the reaction pathway and therefore attains the high selectivity for CO production. This study exemplifies that the microstructure design can modulate the thermodynamic and kinetic factors of photochemical reaction and thereby achieve potential solar-to-chemical energy conversion.

Fundamentals and applications of photo-thermal catalysis

“…In order to reduce the price of the catalysts, non-noble transition metals have also been studied as part of catalysts in photo-thermocatalytic reactions as a more economical option. Ning et al synthesized a hybrid carbon-based catalyst with embedded Co NPs together with dispersed Co-N species, denoted as Co@CoN & C. 194 The reactions were carried out at 55 kPa, using an equal amount of CO 2 and H 2 (1 : 1) and a Xe lamp in a batch reactor. Initially, the photoinduced thermal-effect was demonstrated as evidenced by the increase of temperature of the catalyst surface during the reaction, which reached 518 1C, while the plain Co NP system increased only up to 300 1C.…”

A Metal‐Segregation Approach to Generate CoMn Alloy for Enhanced Photothermal Conversion of Syngas to Light Olefins

“…The high‐resolution Co 2p spectrum for the Co 1 Mn x /(MnO) 2 − x catalyst reveals three clear doublets of Co 2p 3/2 and Co 2p 1/2 in Figure 3B. The peaks at 778.2/794.1 eV can be attributed to Co 0 , with another two binding energies of Co x + 2p 3/2 and Co x + 2p 1/2 peaks located at 780.4 and 796.3 eV, respectively [6a,20] . Therefore, Co species in the fresh Co 1 Mn x /(MnO) 2 − x catalysts are mainly in metallic state, whereas Mn species have both metallic and oxidized states.…”

“…[ 5 ] This method can realize photophysical light‐to‐heat conversion and then drives the chemical reaction on the catalyst surface without additional heating, but even exhibits superior activity compared with thermal catalysis. [ 6 ] Thus, photothermal catalysis has been considered as a green and sustainable way to utilize the most abundant solar energy to convert syngas into valuable chemicals. [ 7 ]…”

Plasmonic photothermal catalysis for solar-to-fuel conversion: current status and prospects

“…Ouyang and co-authors employed atomic-scale dispersed Co–N species anchored Co@C hybrid structure (Co@CoN&C) nanomaterials for CO 2 photothermal reduction, and a CO 2 conversion rate of 132 mmol g −1 h −1 with suppressed undesirable methanation was achieved in a batch-type reaction system under the irradiation of a 300 W Xe lamp. 91 However, under the same conditions, Co nanoparticles demonstrated a reaction rate of only 27 mmol g −1 h −1 . The temperature of the catalysts during the reaction was measured with an infrared thermometer, and a surface temperature of approximately 518 °C was detected over Co@CoN&C, higher than over Co nanoparticles (330 °C) under the same conditions.…”