Applied Catalysis B: Environmental 202 (2017) 314–325 Contents lists available at ScienceDirect Applied Catalysis B: Environmental j ourna l h omepa ge: www.elsevier.com/locate/apcatb Facile decoration of carbon fibers with Ag nanoparticles for adsorption and photocatalytic reduction of CO 2 Jie Ding a,b , Yunfei Bu a,c , Man Ou a,c , Yang Yu a,c , Qin Zhong a,c,∗ , Maohong Fan b,∗∗ a School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, PR China b Department of Chemical and Petroleum Engineering, University of Wyoming, Laramie, WY 82071, USA c Nanjing AIREP Environmental Protection Technology Co., Ltd., Nanjing, Jiangsu 210091, PR China a r t i c l e i n f o Article history: Received 10 February 2016 Received in revised form 17 August 2016 Accepted 20 September 2016 Available online 20 September 2016 Keywords: CO2 Photocatalysis Ag nanoparticles Carbon fibers Gas-solid systems a b s t r a c t Carbon fibers (CFs) decorated with Ag nanoparticles (Ag NPs), hereafter denoted as Ag NPs/CFs, have been successfully synthesized via a simple solution dipping combined with an ultrasonic treatment. CFs are decorated by spherical Ag NPs with 20–50 nm diameters mainly consisted of the Ag nanocrystals, which is reduced from Ag + by both CFs and polyviylpyrrolidone (PVP). The aggregation of Ag NPs on the surface of CFs via Ostwald ripening and from the solution are the primarily responsible for the formation of spherical Ag NPs. The as-prepared Ag NPs/CFs Exhibits 4-time higher of photocatalytic activity than the pure Ag NPs, meanwhile enhancing the selectivity to convert CO 2 into CH 3 OH. A possible visible light photocatalytic mechanism for the better performance and selectivity of Ag NPs/CFs is discussed. The significant enhancement of the CO 2 photocatalytic reduction is primarily attributed to the increase of CO 2 adsorption and the efficient electron transfer to CO 2 as well as the active site splitting of CO 2 reduction and H 2 O decomposition. © 2016 Published by Elsevier B.V. 1. Introduction Due to the excessive dependence on fossil resources, global warming and increasing CO 2 emission in the atmosphere are the severe problems faced worldwide. Conversion of CO 2 into clean fuels and energy-rich chemicals could be one of the most efficient solutions to these problems [1,2]. Toward this goal, biomimetic artificial photosynthesis has recently gained much attention as a promising technology for reduction of CO 2 to energy-rich chemicals using solar energy. In this process, the hydrocarbons are produced from photoreduction of CO 2 using H 2 O and solar energy [3,4]. In 1979, Inoue et al. firstly illustrated the photocataytic reduction of CO 2 to form organic compounds by using a photosensitive semicon- ductor [5]. Afterwards, various photocatalytic systems involving transition-metal or metal complexes have been explored toward the photocatalytic CO 2 reduction, but most of them were efficient only with the presences of organic solvents or water-organic sol- vents as sacrificial reductant [6,7]. The photocatalytic systems using ∗ Corresponding author at: School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, PR China. ∗∗ Corresponding author. E-mail addresses: zq304@mail.njust.edu.cn (Q. Zhong), mfan@uwyo.edu (M. Fan). H 2 O as the reductant for CO 2 reduction still need to be developed. Extensively researchers started with the semiconductors such as TiO 2 or TiO 2 -based heterogeneous photocatalysts due to their low cost and high chemical stability [8]. However, the flat-band poten- tial of electrons in the conduction band of these semicondutors is lower than that required for CO 2 photoreduction, thus result- ing in low efficiency [9]. Therefore, metal catalysts like Au, Ag and Pt series type photocatalysts for CO 2 reduction have gradually attracted attention not only due to their efficiently surface Plasmon resonance under visible light but also stably photocatalytic activity in the whole solar spectral region [10,11]. Unfortunately, most of these catalysts still exhibit low catalytic activity or selectivity for CO 2 reduction because of the easy recombination of their Plasmon- induced electron-hole pairs generated by the electron excitations from HOMO to LOMO [12,13]. Previous studies have reported that the acceleration of electron transfer to CO 2 benefited the separation of electron-hole pairs [14–16]. Therefore, large amounts of efforts have been made to improve the electron transfer in recent years. For example, Lim et al. embedded S or As into the Ag based catalysts to improve the free electron transfer and minimize the overpoten- tial, resulting in the significant promotion of CO 2 photoreduction [14]. Yang et al. prepared the Ag/Pt clusters loaded on TiO 2 (101) or Ag clusters loaded on Ga 2 O 3 to improve the enhancement of CO 2 photoreduction through the facilitation of the electron trans- fer from catalysts to CO 2 [15]. Cheng et al. utilized Pt to modify http://dx.doi.org/10.1016/j.apcatb.2016.09.038 0926-3373/© 2016 Published by Elsevier B.V.