Self-nitrogen-doped carbon spheres assisted CeO2 composites as a bifunctional adsorbent/photocatalyst for CO2 photoreduction

Abstract

It is rather essential to increase CO2 adsorption and improve separation efficiency of photoinduced carriers by solar-driven CO2 reduction. Herein, we proposed a facile approach to synthesize millimeter-sized polyacrylonitrile-based carbon spheres (PANACSs) as a bifunctional adsorbent and self-nitrogen-doped source under a mild condition, and then embeds the highly active CeO2 to construct a CeO2@PANACSs composite with strong adsorption capacity and high reduction activity. The involved XRD, XPS, SEM, N2 adsorption/desorption, CO2 adsorption, UV–vis DRS, EIS, PL and In situ FTIR spectra were characterized. Results suggested that the obtained PANACSs can act as a catalyst to drive the reduction of CO2 into CO under visible light irradiation. CeO2@PANACSs showed the highest performance of photocatalytic reduction of CO2 for 10 h (210.65 μmol·g−1), and the yield of CO evolution is approximately 1.83 times and 17.42 times higher than that of pristine CeO2 and PANACSs, respectively. We found that the existence of nitrogen-containing functional groups further promoted the adsorption and activation of CO2. Among them, pyridinic nitrogen and pyrrolic nitrogen can be used as adsorption and activation sites to accelerate the separation and transfer of e--h+. Furthermore, Ce4+ on the surface of CeO2 acts as an electron capture agent, which captures the electrons that are not transferred in time and reduces itself to Ce3+, and then the formed Ce3+ reduces the adsorbed CO2 to CO. Finally, the possible mechanism is proposed to depict the photocatalytic CO2 reduction over the CeO2@PANACSs. Our finding provides a noteworthy promising strategy to construct bifunctional composite photocatalysts for achieving the high-efficient CO2 adsorption and photoreduction to CO.