Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman Ni-embedded TiO 2 -ZnTiO 3 reducible perovskite composite with synergistic effect of metal/support towards enhanced H 2 production via phenol steam reforming Khaled Saeed Baamran, Muhammad Tahir ⁎ Chemical Reaction Engineering Group (GREG), Department of Chemical Engineering, School of Chemical and Energy Engineering, Faculty of Engineering, Universiti Tecknologi Malaysia, 81310, UTM, Johor Bahru, Johor, Malaysia ARTICLE INFO Keywords: Phenol steam reforming Hydrogen production ZnTiO 3 cubic perovskite Metal-support interaction Anatase/rutile facets of TiO 2 Reducible NiO/TiO 2 ABSTRACT Highly reducible Ni-dispersed TiO 2 -ZnTiO 3 perovskite nanocomposite with different anatase/rutile contents of TiO 2 for enhanced phenol steam reforming (PSR) towards selective H 2 production has been investigated. In-situ growth of TiO 2 nanoparticles (NPs) over ZnTiO 3 cubic perovskite was obtained through hydrothermal assisted impregnation method. TiO 2 -ZnTiO 3 composite performance was entirely dependent on the Zn/Ti molar ratios. With Zn/Ti molar ratio of 2, 19.80% TiO 2 rutile phase in TiO 2 -ZnTiO 3 composite was obtained, giving highest catalytic activity for H 2 production. Using 10% Ni supported TiO 2 -ZnTiO 3 , phenol conversion and H 2 yield of 89.10% and 75.60%, respectively were attained, while it was only 44.60% and 63.32% with 10% Ni/TiO 2 NPs. This was obviously due to strong metal-support interaction with higher Ni-dispersion. More importantly, CO yield with Ni/TiO 2 was 9.68%, decreased to 6.49% using 10% Ni/TiO 2 -ZnTiO 3 perovskite composite, resulting in lower CO/CO 2 ratio and trivial coke formation. Besides, Ni/TiO 2 -ZnTiO 3 composite gave stability for more than 50 h without obvious deactivation, while it was only 6 h over Ni/TiO 2 NPs. The effect of operating para- meters reveals that reaction temperature 700 °C, catalyst loading 0.3 g and phenol/water ratio 5/95 wt% gave the highest catalyst activity. Besides, activity was also enhanced with increasing GHSV (mL.g -1 .h -1 ), which confirms external mass transfer limitation. In conclusion, strong metal-supports interactions in Ni/TiO 2 -ZnTiO 3 composite provide higher Ni-dispersion for stimulating catalytic activity and can be considered as a promising material for hydrogen production applications. 1. Introduction The continuous depletion of fossil fuels reserves and environmental issues with increasing energy demand and greenhouse gases emission (GHGs) have stimulated researches towards renewable and clean en- ergy sources [1]. Hydrogen (H 2 ) as a clean fuel is promising to replace fossil fuels due to its high energy efficiency, zero GHGs emission and can be produced from renewable sources [2]. Among the different technologies, reforming is an attractive approach for H 2 production using abundantly available waste feed stock. Phenol is a prospective biomass derived feedstock generated from petroleum refineries as a waste material or tar byproducts [3,4]. It is also a primary compound of the bio-oil pyrolysis in the modern bio-refining industry, producing in parallel with large amounts of water, and causing rust and corrosion in the pipelines [5–7]. Therefore, it is promising to develop on-site and efficient chemical processes for H 2 production from a mixture of phenol/water via steam reforming technology. Steam reforming of phenol is an efficient route because the waste heat from the pyrolysis and gasification process can be used as input energy in reforming process to preheat the feed mixture [8–11]. However, in phenol steam reforming (PSR), a major challenge is the endothermic nature of reaction which has network of several side re- actions such as water gas shift (WGS) and phenol decomposition, pro- ducing carbon dioxide, carbon monoxide and most important and detrimental; coke [12–14]. To overcome this impediment, several cat- alytic systems for PSR reaction including noble/precious metals and non-noble/transition metals have been investigated. For example, Polychronopoulou et al. [15], investigated phenol steam reforming reaction over Rh-supported Mg-Ce-Zr-X-O-based mixed metals (X = La, Sr, Ba, Ca and Zn) and reported that Rh/Mg-Ce-Zr-La-O at 655 °C ex- hibited H 2 yield of ~95% with lowest CO/CO 2 ratio. Similarly, Domna et al. [11,16], reported that Rh/Ce 0.13 Zr 0.83 La 0.04 O 2 catalyst showed https://doi.org/10.1016/j.enconman.2019.112064 Received 22 June 2019; Received in revised form 9 September 2019; Accepted 10 September 2019 ⁎ Corresponding author. E-mail address: mtahir@cheme.utm.my (M. Tahir). Energy Conversion and Management 200 (2019) 112064 0196-8904/ © 2019 Elsevier Ltd. All rights reserved. T