Conversion of carbon dioxide (CO ) into valuable chemicals, especially liquid fuels, through electrochemical reduction driven by sustainable energy sources, is a promising way to get rid of dependence on fossil fuels, wherein developing of highly efficient catalyst is still of paramount importance. In this study, as a proof-of-concept experiment, first a facile while very effective protocol is proposed to synthesize amorphous Cu NPs. Unexpectedly, superior electrochemical performances, including high catalytic activity and selectivity of CO reduction to liquid fuels are achieved, that is, a total Faradaic efficiency of liquid fuels can sum up to the maximum value of 59% at -1.4 V, with formic acid (HCOOH) and ethanol (C H O) account for 37% and 22%, respectively, as well as a desirable long-term stability even up to 12 h. More importantly, this work opens a new avenue for improved electroreduction of CO based on amorphous metal catalysts.

Formic acid (HCOOH) is one of the most promising chemical fuels that can be produced through CO 2 electroreduction. However, most of the catalysts for CO 2 electroreduction to HCOOH in aqueous solution often suffer from low current density and limited production rate. Herein, we provide a bismuth/cerium oxide (Bi/CeO x) catalyst, which exhibits not only high current density (149 mA cm À2), but also unprecedented production rate (2600 mmol h À1 cm À2) with high Faradaic efficiency (FE, 92 %) for HCOOH generation in aqueous media. Furthermore, Bi/CeO x also shows favorable stability over 34 h. We hope this work could offer an attractive and promising strategy to develop efficient catalysts for CO 2 electroreduction with superior activity and desirable stability. Excessive CO 2 emission has brought about severe problems related to resources, environment, and climate. Thus, converting CO 2 into valuable chemical fuels attract more and more research attention. [1] Among the various conversion approaches, electrochemical reduction of CO 2 in aqueous media is more favorable because it can make better use of electricity generated from sustainable sources without producing any additional CO 2. [1-5] Nevertheless, low activity, selectivity and stability of catalysts are still the big challenges for CO 2 electroreduction. Therefore, developing efficient electrocatalysts for CO 2 reduction is highly desired. As one of the most attractive CO 2 reduction products, formic acid (HCOOH) is widely identified as a desirable hydrogen carrier. [6-10] Up to now, many metallic catalysts, including Cd, Hg, Pd, Pb, In, Sn and Bi are found to be effective to form HCOOH (or formate) through CO 2 electroreduction. [11-29] However, the activities are still very low even using the toxic or noble metals. As well as we know, the current density and production rate (in H-type reaction cell) by far are less than 80 mA cm À2 , and 1500 mmol h À1 cm À2 , respectively. [11-29] On the other side, high applied potentials and current density always lead to the low Faradaic efficiency (FE) due to the severe competitive hydrogen evolution reaction (HER). [25] Therefore, achieving a low-cost, eco

No abstract

have been dedicated to produce HCOOH (or HCOO − ) through ERC. Several metals, such as Pd, Pb, Hg, In, and Cd, exhibit good selectivity for HCOOH, while some of them are plagued by the shortcomings of scarcity, high cost or toxicity. [19][20][21][22] Besides, many catalysts exhibit low cathodic energy efficiency (EE), indicating the large energy consumption, because of the high overpotential and low Faradaic efficiency (FE) of products. [14] Therefore, developing the resource-abundant catalysts with high FE and low overpotential to increase EE is significant while still very challenging.Theoretically, Bi might be an intriguing catalyst for ERC as it is ecofriendly, costeffective, and inferior for H 2 evolution. There are several reports on the carbon monoxide (CO) production in ionic liquid electrolyte by using Bi-based materials. [23][24][25][26] However, ERC is more appealing in aqueous solution for practical application. Recently, some efforts have been dedicated to the HCOOH (or HCOO − ) production in aqueous solution over Bi-based catalysts. [27][28][29][30][31] Moreover, Bi shows a relatively positive electrode potential, which is conducive to obtain the high cathodic EE and long-term stability. Thus, it is desired to improve Bi-based catalysts with high selectivity and cathodic EE for HCOOH production in aqueous solution.Herein, the ultrafine Bi nanoparticles (NPs) anchored on reduced graphene oxide (Bi/rGO) is synthesized and employed for ERC in 0.1 m KHCO 3 electrolyte. As a result, the synthesized Bi/rGO endows the ERC with excellent performance under normal pressure and room temperature. It almost outperforms all recently reported electrocatalysts with the highest 98% FE and meanwhile a high cathodic EE of 71% for HCOOH at −0.8 V versus RHE (the voltages reported here are against RHE unless noted), which is also comparable with the most existing catalysts for the HCOOH production. Moreover, the obtained FE of HCOOH and current density show negligible deterioration over 12 h, illustrating the favorable stability of Bi/ rGO.Bi/rGO is synthesized through a facile reduction route by using a reducing agent of sodium borohydride. For comparison, pure Bi and Bi-PVP using the polyvinylpyrrolidone (PVP) as the dispersant are also prepared as well. As shown in Figure 1a, the diffraction peaks of all three samples can be assigned to metallic Bi (JCPDS: 44-1246). [32] Additionally, high-resolution X-ray photoelectron spectroscopy (XPS) spectra (Figure 1b) also manifest that only Bi metal exists in all samples. The Bi 4f signals at 156.8 and 162.1 eV for Bi-PVP and pure Bi are in the The electroreduction of carbon dioxide (CO 2 ) to value-added fuels is of great significance to meet the ever-increasing energy and environmental challenges. So far, desirable selectivity and Faradaic efficiency for CO 2 reduction can be obtained over most electrocatalysts. However, improving cathodic energy efficiency is still neglected in research. Herein, a facile reduction method is first presented to synthesize the ultrafine non-n...

No abstract