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Abstract: Electrochemical carbon dioxide (CO2) reduction can produce valuable carbonaceous compounds that are in significant demand, due to its ability to decrease the accumulated atmospheric CO2 and improve the intermittent nature of renewable energy sources. Considering the sluggish kinetics of CO2 reduction reaction, the multielectron–proton transfer process, and the inevitable mixed reduction products, designing efficient and robust electrocatalysts that benefit from the structure–activity relationship is the focus to promote CO2 conversion. In this review, various metal‐based materials are first classified and discussed in terms of their structural and elemental compositions for catalytic behaviors. Afterward, the most intrinsic microstructural/electronic effects as well as the influence of compositional alteration on the catalyst activity, selectivity, and stability are summarized. Additionally, recent attempts to develop the assigned electrochemical cells are surveyed and described from a technological point of view. [ABSTRACT FROM AUTHOR]

Metallic actuators have received a wide range of attention in the past two decades because of their larger strains than piezoelectric ceramics and higher strength relative to conducting polymers. However, the metallic actuators composed of noble metals are limited to the high material cost for further development and practical applications. Here, nanoporous CuMnNi (np‐CMN) alloys are fabricated from a ternary Mn70Cu20Ni10 precursor through an electrochemical dealloying method, and their microstructures/compositions are further regulated through different electrochemical processes (multi‐step and two‐step). The np‐CMN alloys show good electrochemical actuation properties in 1 m NaOH solution, and the sample obtained from two‐step dealloying exhibits much better actuation performance than that from multi‐step dealloying. The maximum strain amplitude of np‐CMN could reach up to 0.46%, which is comparable to or even better than that of noble metal‐based actuators. Our work indicates that the low‐cost np‐CMN alloy could be a competitive material among electrochemical metallic actuators. [ABSTRACT FROM AUTHOR]

A surface reconstructing phenomenon is discovered on a defect‐rich ultrathin Pd nanosheet catalyst for aqueous CO2 electroreduction. The pristine nanosheets with dominant (111) facet sites are transformed into crumpled sheet‐like structures prevalent in electrocatalytically active (100) sites. The reconstruction increases the density of active sites and reduces the CO binding strength on Pd surfaces, remarkably promoting the CO2 reduction to CO. A high CO Faradaic efficiency of 93 % is achieved with a site‐specific activity of 6.6 mA cm−2 at a moderate overpotential of 590 mV on the reconstructed 50 nm Pd nanosheets. Experimental and theoretical studies suggest the CO intermediate as a key factor driving the structural transformation during CO2 reduction. This study highlights the dynamic nature of defective metal nanosheets under reaction conditions and suggests new opportunities in surface engineering of 2D metal nanostructures to tune their electrocatalytic performance. [ABSTRACT FROM AUTHOR]

A surface reconstructing phenomenon is discovered on a defect‐rich ultrathin Pd nanosheet catalyst for aqueous CO2 electroreduction. The pristine nanosheets with dominant (111) facet sites are transformed into crumpled sheet‐like structures prevalent in electrocatalytically active (100) sites. The reconstruction increases the density of active sites and reduces the CO binding strength on Pd surfaces, remarkably promoting the CO2 reduction to CO. A high CO Faradaic efficiency of 93 % is achieved with a site‐specific activity of 6.6 mA cm−2 at a moderate overpotential of 590 mV on the reconstructed 50 nm Pd nanosheets. Experimental and theoretical studies suggest the CO intermediate as a key factor driving the structural transformation during CO2 reduction. This study highlights the dynamic nature of defective metal nanosheets under reaction conditions and suggests new opportunities in surface engineering of 2D metal nanostructures to tune their electrocatalytic performance. [ABSTRACT FROM AUTHOR]

Polynary single‐atom structures can combine the advantages of homogeneous and heterogeneous catalysts while providing synergistic functions based on different molecules and their interfaces. However, the fabrication and identification of such an active‐site prototype remain elusive. Here we report isolated diatomic Ni‐Fe sites anchored on nitrogenated carbon as an efficient electrocatalyst for CO2 reduction. The catalyst exhibits high selectivity with CO Faradaic efficiency above 90 % over a wide potential range from −0.5 to −0.9 V (98 % at −0.7 V), and robust durability, retaining 99 % of its initial selectivity after 30 hours of electrolysis. Density functional theory studies reveal that the neighboring Ni‐Fe centers not only function in synergy to decrease the reaction barrier for the formation of COOH* and desorption of CO, but also undergo distinct structural evolution into a CO‐adsorbed moiety upon CO2 uptake. [ABSTRACT FROM AUTHOR]

Polynary single‐atom structures can combine the advantages of homogeneous and heterogeneous catalysts while providing synergistic functions based on different molecules and their interfaces. However, the fabrication and identification of such an active‐site prototype remain elusive. Here we report isolated diatomic Ni‐Fe sites anchored on nitrogenated carbon as an efficient electrocatalyst for CO2 reduction. The catalyst exhibits high selectivity with CO Faradaic efficiency above 90 % over a wide potential range from −0.5 to −0.9 V (98 % at −0.7 V), and robust durability, retaining 99 % of its initial selectivity after 30 hours of electrolysis. Density functional theory studies reveal that the neighboring Ni‐Fe centers not only function in synergy to decrease the reaction barrier for the formation of COOH* and desorption of CO, but also undergo distinct structural evolution into a CO‐adsorbed moiety upon CO2 uptake. [ABSTRACT FROM AUTHOR]

Transition metal nitrogen carbon based single‐atom catalysts (SACs) have exhibited superior activity and selectivity for CO2 electroreduction to CO. A favorable local nitrogen coordination environment is key to construct efficient metal‐N moieties. Here, a facile plasma‐assisted and nitrogen vacancy (NV) induced coordinative reconstruction strategy is reported for this purpose. Under continuous plasma striking, the preformed pentagon pyrrolic N‐defects around Ni sites can be transformed to a stable pyridinic N dominant Ni‐N2 coordination structure with promoted kinetics toward the CO2‐to‐CO conversion. Both the CO selectivity and productivity increase markedly after the reconstruction, reaching a high CO Faradaic efficiency of 96% at mild overpotential of 590 mV and a large CO current density of 33 mA cm‐2 at 890 mV. X‐ray adsorption spectroscopy and density functional theory (DFT) calculations reveal this defective local N environment decreases the restraint on central Ni atoms and provides enough space to facilitate the adsorption and activation of CO2 molecule, leading to a reduced energy barrier for CO2 reduction. [ABSTRACT FROM AUTHOR]