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In this paper, Bi2O3 electrocatalysts for the electroreduction of CO2 to formate were synthesized with different morphologies, including nanoparticles and thin nanorods. Comparatively, Bi2O3 nanoparticles have higher catalytic activity than Bi2O3 thin nanorods. The Faradaic efficiency of formate formation at a moderate potential of −1.2 vs. RHE in aqueous solution could reach 91 %. In addition, a maximum current density for formate production of up to 22 mA cm−2 was achieved, which is almost 3 times higher than that of Bi2O3 thin nanorods. In particular, the catalytic activity of the Bi2O3 nanoparticle catalyst was almost stable over a 23‐hour period of electrolysis, exhibiting its application prospect in the electroreduction of CO2 to formate. Upcycling: nanoparticles and thin nanorods of Bi2O3 as catalysts for the electroreduction of CO2 to formate are synthesized. The Bi2O3 nanoparticles show higher catalytic activity than the thin nanorods. A Faradaic efficiency of 91 % at a moderate potential of −1.2 vs. RHE is found in aqueous solution. A maximum current density of up to 22 mA cm−2 is achieved, with a stable activity over a 23‐hour period of electrolysis. [ABSTRACT FROM AUTHOR]

Electrocatalytic CO2 reduction reaction (CRR) is a promising way to convert carbon dioxide (CO2) into value‐added hydrocarbons to alleviate the ever‐increasing environmental problem and accelerate the realization of carbon cycling. Cost‐effective and stable electrocatalytic materials with low overpotential, superior selectivity, excellent activity and great stability are critically important to achieve such a target. Cu‐based electrocatalysts are promising candidates for electrochemical CRR due to their versatile abilities of converting CO2 into various products. This review analyzes and summarizes the current progress in utilization of Cu‐based catalytic materials for electrochemical CRR. Monometallic, bimetallic, trimetallic, and multimetallic Cu‐based electrocatalysts with variable elemental compositions and tunable morphologies, including Cu nanowires, Cu nanocubes (NCs), Cu porous structures, Cu‐based alloys, Cu‐oxide/hydrogen oxide, Cu single atoms, and 2D substrate‐supported Cu electrocatalysts for CRR, are surveyed. Substantial advances in overcoming the existing bottlenecks of eletrocatalysts and effectively improving CRR performance of Cu‐based electrocatalysts for future applications are systematically discussed. Challenges and perspectives of Cu‐based electrocatalytic materials for CRR are also offered, which may shed light on further development of Cu‐based electrocatalysts with superior performance. It is anticipated that this review will provide a valuable insight into the rational design and synthesis of highly efficient Cu‐based electrocatalysts for large‐scale CRR utilization. [ABSTRACT FROM AUTHOR]

Copper (Cu)-based materials for efficient CO2 conversion to adjustable syngas are reported. We employ an energy-efficient microwave-assisted route to synthesize copper/copper oxides with different structures and morphologies. The initial oxidation state of the copper on the surface significantly influences the performance of the materials in the CO2 reduction reaction (CO2RR). On the as-prepared material surface, a high content of Cu2O improves the selectivity toward CO and consequently the catalyzed CO2RR produce a syngas with a low H2/CO ratio, while the CuO performs poorly. In particular, Cu2O particles with a cubic shape show the highest selectivity for the CO formation. The superior catalytic activity of the Cu2O cubes for the CO2RR is attributed to the surface roughening under potential, which offers abundant electrochemically active sites and facilitates mass transport. [ABSTRACT FROM AUTHOR]

Abstract: CO2 electrochemical reduction offers a potential technique to decrease the CO2 emission levels, but it has been hindered by the poor performance of electrocatalysts. In this work, the electrochemical reduction of CO2 has been studied by using a needle‐like porous indium electrode, which was electrodeposited in aqueous electrolytes containing Cl− using the hydrogen bubble dynamic template. This novel electrode displayed improved electrocatalytic activity, enhanced conversion efficiencies, and a lower onset potential −0.76 V vs. RHE), which was 0.3 V less than the indium foil electrode. Moreover, it exhibited enhanced faradaic efficiencies of 86 % for formate at −0.86 V vs. RHE and with a current density of 5.8 mA cm−2. This excellent catalytic activity is the result of a large electrochemical surface area and needle‐like dendrite structures in the presence of Cl− salts. Utilization of the novel nanostructured electrocatalysts and understanding of the role of salts can contribute to further improvements in CO2 reduction. [ABSTRACT FROM AUTHOR]

Among many alternatives, CO2 electroreduction (CO2ER) is an emerging technology to alleviate its level in the atmosphere and simultaneously to produce essential products containing high energy density using various electrocatalysts. Cu‐based mono‐ and bimetallics are electrocatalysts of concerns in this work due to the material's abundance and versatility. Intrinsic factors affecting the CO2ER are first analyzed, whereby understanding and characterizing the surface features of electrocatalysts are addressed. An X‐ray absorption spectroscopy‐based methodology is discussed to determine electronic and structural properties of electrocatalyst surface which allows the prediction of reaction mechanism and establishing the correlation with reduction products. The selectivity and faradaic efficiency of products highly depend on the quality of surface modification. Preparation and modification of electrocatalyst surfaces through various techniques are critical to increase the number of activity sites and the corresponding site activity. Mechanisms of CO2ER are complicate and thus are discussed in accordance with main products of interests. The authors try to concisely compile the most interesting, recent, and reasonable ideas that are agreeable to experimental results. Finally, this review provides an outlook for designing better Cu and Cu‐based bimetallic catalysts to obtain selective products through CO2ER. This review identifies the gaps in CO2ER and forward new insights via detailed electronic and structural characterizations of Cu‐based bimetallic and monometallic electrocatalysts. Intrinsic factors affecting CO2ER and the reduction mechanism are discussed, as well as characterization techniques for Cu–M bimetallics or alloys. Due to the range of versatile products, selectivity of the electrocatalysts is also reviewed. [ABSTRACT FROM AUTHOR]