Contents lists available at ScienceDirect Journal of CO 2 Utilization journal homepage: www.elsevier.com/locate/jcou AuAg/ZnO nanocatalyst for CO 2 valorization and H 2 and CO electrochemical production Maria Sarno a,b, *, Eleonora Ponticorvo b , Stefano Piotto c , Anna Maria Nardiello c , Salvatore De Pasquale a,b , Nicola Funicello a a Department of Physics "E.R. Caianiello", University of Salerno, via Giovanni Paolo II, 132 – 84084, Fisciano, SA, Italy b Nano_Mates (Research Centre for Nanomaterials and Nanotechnology at the University of Salerno), University of Salerno, via Giovanni Paolo II, 132 – 84084, Fisciano, SA, Italy c Department of Pharmacy, University of Salerno, via Giovanni Paolo II, 132 – 84084, Fisciano, SA, Italy ARTICLE INFO Keywords: Carbon dioxide reduction Nanomaterials Syngas AuAg/ZnO DFT calculation ABSTRACT A controllable composition and morphology AuAg/ZnO catalyst, prepared by an easily scalable method, was, for the first time, explored for the electrocatalytic reduction of CO 2 . It was found that the composition of the bimetallic alloy contributes to the overall CO 2 reduction performance. In particular, as also demonstrated by density functional theory calculations, CO production increases, decreasing the Au content in the catalyst alloy. The experimental investigation reveals that the products are H 2 and CO, which production rate increases in the presence of ZnO, up to a Faradic efficiency of 94.7 % at 0.4 V. On the other hand, controlling the oleic acid covering it is possible to modulate the surface properties allowing to obtain, at 0.6 V, H 2 /CO ratios equal to 1.1 and 1.9 for nanocatalysts thermally treated for 2 and 5 h, respectively. 1. Introduction Carbon dioxide, which is the main greenhouse gas, represents today one of the major reasons of global temperature increase. One of the possible ways to reduce CO 2 emission is to capture and eventually va- lorize it [1–8]. In this scenario, the main challenge is to develop new solutions with low environmental impacts. On the other hand, CO 2 , through a chemical way and use of non-fossil energy, can be trans- formed into chemicals, pharmaceuticals, or biofuels, e.g., syngas for mediated productions. Electricity supplied from renewable energy sources allows for a sustainable CO 2 electrocatalytic reduction, i.e., transformation in fuels and chemicals [1–6]. So far research has focused its effort on the identification of suitable electrocatalysts and optimized process conditions for the selective synthesis of specific molecules, i.e., selective reduction of CO 2 vs. CO, CH 3 OH, etc... [9,10]. More recently, morphology control, catalyst composition, support effect, and adjustment of precisely exposed crys- tallographic facets [11] were identified as the key parameters to im- prove activity and selectivity [12]. On the other hand, cheap, selective, durable electrocatalysts, obtained by massive production approaches and able to overcome the main electrochemical limitations, e.g., a large number of possible intermediates formed [13–16], are still to be de- veloped. Although the catalytic activity of different metals has been demonstrated [2,4,17–19], finding selective, durable and cheap elec- trocatalysts operating at, as low as possible, overpotentials are still challenging and obliged to look for alternative solutions based on the combined use of different species. Bimetallic electrocatalysts have been established as a good cheaper way to reduce the number of produced species versus mainly HCOOH or CO compounds [10,12,13,20–24]. This is because the electronic structures of each component are mod- ified and altered by the alloy formation [19]. On the other hand, the observation that hydrogen evolution reac- tion (HER) is an inevitable rival reaction of the reduction of CO 2 in aqueous media, suggests attempting for a competitive approach, in search for the simultaneous CO 2 conversion and hydrogen production. The achievement of this goal requires the design of a catalyst capable, by virtue of multi-functionalities and multi-constituents, to produce controlled compositions: from CO to syngas with specific ratios. As far as literature is concerned, there are only a small number of papers re- porting the controlled production of H 2 and CO during the electro- chemical reduction of CO 2 [25,26]. With the purpose of moving effec- tively in this direction, there is a need to design new catalysts capable of fulfilling the requirements of the process through multiple functions. It is, in general, difficult, to predict the behavior of a new nanocatalyst. This is mainly because of the nanostructured catalyst nature and var- iances between different catalysts produced in different ways. On the https://doi.org/10.1016/j.jcou.2020.101179 Received 9 January 2020; Received in revised form 12 April 2020; Accepted 16 April 2020 ⁎ Corresponding author at: Department of Physics "E.R. Caianiello", University of Salerno, via Giovanni Paolo II, 132 – 84084, Fisciano, SA, Italy. E-mail address: msarno@unisa.it (M. Sarno). Journal of CO₂ Utilization 39 (2020) 101179 2212-9820/ © 2020 Elsevier Ltd. All rights reserved. T