The mesostructured NiO/Ni composites boost the electrochemical energy storage performance of NiO to its theoretical limit, which results from the synergism of high accessibility to electrolyte, short solid-state ion diffusion length and high conductivity owing to the unique mesostructure.

carbon sources through different technical routes, [1] which either have negative environmental impacts or deliver a poor atomic economy while being energy intensive. [2] For instance, the life-cycle greenhouse gas emission for producing a liter of bioethanol is ≈1.6 kg CO 2 equivalent. [3] For fuel ethanol with a global production of ≈104 billion liters per year, [4] the annual CO 2 emission is more than 170 million metric tons, corresponding to 0.5% of the global annual overall carbon emission. [5] New technologies are thus in demand to balance the target of environmental protection and economic development. Electrochemical CO 2 reduction (ECR) driven by renewable energies is a competitive candidate, as it converts CO 2 into liquid products like formate and alcohols with nearly net-zero CO 2 emissions. [6] Nonetheless, the Faradaic efficiency (FE) for CO 2-to-alcohol production generally remains low, typically less than 50%. [7] For instance, Gewirth and co-workers presented a nanoporous Cu-Ag alloy for the enhancement of ECR activity, with an FE toward ethanol of ≈25%. [8] Bell and co-workers reported a Cu-Ag alloy with stain effect, and the total FE of alcohol production was less than 15%. [9] Recently, Sargent and co-workers reported an enhancement of ethanol selectivity in a flow cell system by tuning binding site diversity in an Ag/ Cu catalyst, while the FE for ethanol was still less than 50%. [10] The challenge in developing effective strategies of tuning the energetics of reaction pathways limits the CO 2-to-alcohol selectivity. Based on the theoretical and experimental studies, [11] ethylene (C 2 H 4) generally dominates the C 2+ product distribution, with a theoretical prediction of an alcohol/ethylene ratio of 35:65. [12] However, Calle-Vallejo and Koper reported that ethanol presents a lower free energy position compared to ethylene in the entire reaction route of carbon monoxide (CO) electroreduction to C 2 products. [13] The poor alcohol selectivity has been attributed to the unfavorable adsorption of key intermediates in the ethanol pathway on copper, [13] such as CH 3 CHO* and CH 3 CH 2 O* proved by Chorkendorff and co-workers. [14] Thus, it is rational to hypothesize that an enhanced alcohol selectivity may arise from modulating the adsorption of key intermediates like CH 3 CH 2 O* in the ECR pathways. In addition, it is also well known that Ag component can suppress hydrogen Copper-based catalysts electrochemically convert CO 2 into multicarbon molecules. However, the selectivity toward alcohol products has remained relatively low, due to the lack of catalysts favoring the adsorption of key intermediates in the alcohol pathways. Herein, a Cu 3 Ag 1 electrocatalyst is developed using galvanic replacement of an electrodeposited Cu matrix. The Cu 3 Ag 1 electrocatalyst enables a 63% Faradaic efficiency for CO 2-to-alcohol production and an alcohol partial current density of −25 mA cm −2 at −0.95 V versus reversible hydrogen electrode, corresponding to a 126-fold enhancement in selectivity and 25-...

The continuous increase of CO2 concentration in the atmosphere has been imposing an imminent threat for global climate change and environmental hazards. In recent years, the electrochemical or photochemical conversion of CO2 into value‐added chemicals or fuels has received significant attention, as it may enable an attractive means to mitigate the atmospheric CO2 concentration and complete the imbalanced carbon‐neutral energy cycle, as well as create renewable energy resources for human use. Among the different electrocatalysts being studied, Cu‐based materials have been demonstrated as the only category of candidates that allows the conversion of CO2 into a variety of reducing products, including carbon monoxide, hydrocarbons, and alcohols. Herein, the reaction pathways for different Cu‐based catalysts for C1 and C2+ products are introduced. Then, different parameters in tuning Cu‐based electrocatalysts are summarized and discussed, including the morphologies, compositions, crystal facets, and oxide derivation. In addition, various types of parameters for CO2 electroreduction are also described, particularly the option of electrolytes such as aqueous, ionic liquids, and organic solutions. Finally, the current challenges are discussed and the potential strategies to facilitate the future development of CO2 electroreduction are summarized.

a key factor to evaluate the practicality of electrolysis systems with carbon footprint assessments, [7,8] the electrochemical CO 2to-ethanol production efficiency generally remains unsatisfactory, with Faradaic efficiency of ethanol production (FE ethanol ) typically below 50% and partial current densities (J ethanol ) < 200 mA cm −2 . [9,10] The generally low ethanol selectivity has been suggested due to the unfavorable adsorption of several key intermediates (i.e., *CHCHOH, *CH 2 CHOH, *CH 3 CHOH) in the ethanol formation pathway on Cu surfaces. [11,12] Heteroatomic doping is a potential means to tune the intermediate adsorption capability to improve the ethanol selectivity, which has been reported for Cu−Ag or Cu−Au systems. [13][14][15][16] For instance, Sargent and coworkers reported a bimetallic Cu−Ag catalyst with increased binding site diversity, allowing to reduce the ethylene pathway and achieve a FE ethanol as 41%. [13] A Cu−Au system was reported to increase the *CO coverage, resulting in a selectivity of producing ethanol as 48%. [14] On the other hand, considering the capital investment of the electrolysis technology, [5,6] it is also critical to search for cheap and sustainable catalyst candidates. For instance, replacing Ag with Sn can substantially reduce the catalyst cost. [17] It has also been reported that the surface coverage of *CO plays a critical role in converting CO 2 into ethanol. [18,19] Theoretical calculations of the *CO adsorption capability on Cu−Sn alloy surface have been investigated. For instance, Gokhale and coworkers reported that the existence of Sn atoms in a CuSn alloy led to the compression of Cu atoms and facilitated a higher surface coverage of *CO on Cu sites. [20] Recent studies also confirmed the favored CO-pathway on the Cu-Sn alloys with lower Sn amount (e.g., Cu 3 Sn). [21,22] On the other hand, the concept of entropy has already been introduced for analyses of binary alloys. [23] For example, Takeguchi et al. proposed an entropy-based adsorption theory that alloys with random distributions (defined by coordination state in their work with PtRu alloys) can weaken the adsorption of *CO. [24] Thus, highentropy state CuSn alloys like Cu 6 Sn 5 are possibly not suitable for *CO adsorption, [21] while a low-entropy state CuSn alloy may provide an enhanced capability for *CO adsorption and subsequent enhanced ethanol selectivity.In this work, we developed a low-entropy Cu 3 Sn electrocatalyst with substantially enhanced adsorption of *CO and *CHCHOH as key intermediates for ethanol production, featuring as efficient electrochemical CO 2 reduction to ethanol.Electrochemical carbon dioxide reduction to ethanol suggests a potential strategy to reduce the CO 2 level and generate valuable liquid fuels, while the development of low-cost catalysts with high activity and selectivity remains a major challenge. In this work, a bimetallic, low-entropy state Cu 3 Sn catalyst featuring efficient electrocatalytic CO 2 reduction to ethanol is developed. This low-entropy state Cu 3 Sn ...

A SnO2 nanoparticle-decorated hollow carbon spherical structure with interfacial Sn–O–C linkages was fabricated as an efficient CO2 reduction reaction electrocatalyst.

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Transition metal oxides (TMOs) are promising electrode materials for advanced electrochemical energy storage (EES) due to their high theoretical capacities, but they usually exhibit quite poor practical performance. There is a pressing need to boost their EES performance by electrode engineering directed with a well-defined structure–performance relationship. Herein, we report an efficient approach to improve the specific capacitance and high-rate capability of spinel nickel cobaltite by constructing three-dimensional (3D) hierarchical porous mesostructures. The optimal Ni1.4Co1.6O4 mesostructures assembled from ultrathin nanosheets exhibit high capacitance (2282 F g–1 at 1 A g–1), excellent high-rate capability (1234 F g–1 at 50 A g–1) and good cycling performance, which are significantly superior to the Co3O4 mesostructure counterparts, Ni1.4Co1.6O4 mesostructures assembled from nanowires, and randomly packed Ni1.4Co1.6O4 nanosheets. The excellent performance is attributed to the stable hierarchical porous architecture which enables a large electroactive area and synergistically enhanced electrolyte access, solid-state ion diffusion, and electron transfer. This tactic of constructing a 3D mesostructured electrode with enhanced charge transport can be generalized to other TMOs for improving their EES performances.