Aluminum-copper alloy anode materials for high-energy aqueous aluminum batteries.

Aqueous aluminum batteries are promising post-lithium battery technologies for large-scale energy storage applications because of the raw materials abundance, low costs, safety and high theoretical capacity. However, their development is hindered by the unsatisfactory electrochemical behaviour of the Al metal electrode due to the presence of an oxide layer and hydrogen side reaction. To circumvent these issues, we report aluminum-copper alloy lamellar heterostructures as anode active materials. These alloys improve the Al-ion electrochemical reversibility (e.g., achieving dendrite-free Al deposition during stripping/plating cycles) by using periodic galvanic couplings of alternating anodic α-aluminum and cathodic intermetallic Al2Cu nanometric lamellas. In symmetric cell configuration with a low oxygen concentration (i.e., 0.13 mg L-1) aqueous electrolyte solution, the lamella-nanostructured eutectic Al82Cu18 alloy electrode allows Al stripping/plating for 2000 h with an overpotential lower than ±53 mV. When the Al82Cu18 anode is tested in combination with an AlxMnO2 cathode material, the aqueous full cell delivers specific energy of ~670 Wh kg-1 at 100 mA g-1 and an initial discharge capacity of ~400 mAh g-1 at 500 mA g-1 with a capacity retention of 83% after 400 cycles.

Nanoporous Intermetallic Cu3 Sn/Cu Hybrid Electrodes as Efficient Electrocatalysts for Carbon Dioxide Reduction.

Designing highly selective and cost-effective electrocatalysts toward electrochemical carbon dioxide (CO2 ) reduction is crucial for desirable transformation of greenhouse gas into fuels or high-value chemical products. Here, the authors report intermetallic Cu3 Sn that is in situ formed and seamlessly integrated on self-supported bimodal nanoporous Cu skeleton (Cu3 Sn/Cu) via a spontaneous alloying of Sn and Cu as robust electrocatalyst for selective electroreduction of CO2 to CO. By virtue of Sn atoms strengthening CO adsorption on Cu atoms, the intermetallic Cu3 Sn has an intrinsic activity of ≈10.58 µA cm-2 , more than 80-fold higher than that of monometallic Cu. By virtue of hierarchical bicontinuous nanoporous Cu architecture facilitating electron transfer and CO2 and proton mass transport and offering high specific surface areas for full use of electroactive Cu3 Sn sites, the nanoporous Cu3 Sn/Cu hybrid electrodes produce CO at a low overpotential of 0.09 V, and exhibit high partial current density of ≈15 mA cm-2 geo at overpotential of 0.59 V, along with excellent stability and selectivity of 91.5% Faradaic efficiency. The outstanding electrochemical performance make them attractive alternatives to precious Au- and Ag-based electrocatalysts for building low-cost CO2 electrolyzers to selectively produce CO.

Spontaneously separated intermetallic Co3Mo from nanoporous copper as versatile electrocatalysts for highly efficient water splitting.

Developing robust nonprecious electrocatalysts towards hydrogen/oxygen evolution reactions is crucial for widespread use of electrochemical water splitting in hydrogen production. Here, we report that intermetallic Co3Mo spontaneously separated from hierarchical nanoporous copper skeleton shows genuine potential as highly efficient electrocatalysts for alkaline hydrogen/oxygen evolution reactions in virtue of in-situ hydroxylation and electro-oxidation, respectively. The hydroxylated intermetallic Co3Mo has an optimal hydrogen-binding energy to facilitate adsorption/desorption of hydrogen intermediates for hydrogen molecules. Associated with high electron/ion transport of bicontinuous nanoporous skeleton, nanoporous copper supported Co3Mo electrodes exhibit impressive hydrogen evolution reaction catalysis, with negligible onset overpotential and low Tafel slope (~40 mV dec-1) in 1 M KOH, realizing current density of -400 mA cm-2 at overpotential of as low as 96 mV. When coupled to its electro-oxidized derivative that mediates efficiently oxygen evolution reaction, their alkaline electrolyzer operates with a superior overall water-splitting output, outperforming the one assembled with noble-metal-based catalysts.

Intermetallic Cu5Zr Clusters Anchored on Hierarchical Nanoporous Copper as Efficient Catalysts for Hydrogen Evolution Reaction.

Designing highly active and robust platinum-free electrocatalysts for hydrogen evolution reaction is vital for large-scale and efficient production of hydrogen through electrochemical water splitting. Here, we report nonprecious intermetallic Cu5Zr clusters that are in situ anchored on hierarchical nanoporous copper (NP Cu/Cu5Zr) for efficient hydrogen evolution in alkaline medium. By virtue of hydroxygenated zirconium atoms activating their nearby Cu-Cu bridge sites with appropriate hydrogen-binding energy, the Cu5Zr clusters have a high electrocatalytic activity toward the hydrogen evolution reaction. Associated with unique architecture featured with steady and bicontinuous nanoporous copper skeleton that facilitates electron transfer and electrolyte accessibility, the self-supported monolithic NP Cu/Cu5Zr electrodes boost violent hydrogen gas release, realizing ultrahigh current density of 500 mA cm-2 at a low potential of -280 mV versus reversible hydrogen electrode, with exceptional stability in 1 M KOH solution. The electrochemical properties outperform those of state-of-the-art nonprecious metal electrocatalysts and make them promising candidates as electrodes in water splitting devices.

Flexible Co-Mo-N/Au Electrodes with a Hierarchical Nanoporous Architecture as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction.

Designing highly active and robust electrocatalysts for oxygen evolution reaction (OER) is crucial for many renewable energy storage and conversion devices. Here, self-supported monolithic hybrid electrodes that are composed of bimetallic cobalt-molybdenum nitride nanosheets vertically aligned on 3D and bicontinuous nanoporous gold (NP Au/CoMoNx ) are reported as highly efficient electrocatalysts to boost the sluggish reaction kinetics of water oxidation in alkaline media. By virtue of the constituent CoMoNx nanosheets having large accessible CoMoOx surface with remarkably enhanced electrocatalytic activity and the nanoporous Au skeleton facilitating electron transfer and mass transport, the NP Au/CoMoNx electrode exhibits superior OER electrocatalysis in 1 m KOH, with low onset overpotential (166 mV) and Tafel slope (46 mV dec-1 ). It only takes a low overpotential of 370 mV to reach ultrahigh current density of 1156 mA cm-2 , ≈140-fold higher than free CoMoNx nanosheets. The electrocatalytic performance makes it an attractive candidate as the OER catalyst in the water electrolysis.