Overall Carbon-neutral Electrochemical Reduction of CO2 in Molten Salts using a Liquid Metal Sn Cathode

An overall carbon-neutral CO₂ electroreduction requires enhanced conversion efficiency and intensified functionality of CO₂ -derived products to balance the carbon footprint from CO₂ electroreduction against fixed CO₂ . A liquid Sn cathode is herein introduced into electrochemical reduction of CO₂ in molten salts to fabricate core-shell Sn-C spheres (Sn@C). An in situ generated Li₂ SnO₃ /C directs a self-template formation of Sn@C. Benefitting from the accelerated reaction kinetics from the liquid Sn cathode and the core-shell structure of Sn@C, a CO₂ -fixation current efficiency higher than 84 % and a high reversible lithium-storage capacity of Sn@C are achieved. The versatility of this strategy is demonstrated by other low melting point metals, such as Zn and Bi. This process integrates energy-efficient CO₂ conversion and template-free fabrication of value-added metal-carbon, achieving an overall carbon-neutral electrochemical reduction of CO₂ .

Hydrogen Production and Water Desalination with On-demand Electricity Output Enabled by Electrochemical Neutralization Chemistry

Energy-saving hydrogen production can be achieved by using renewables or decoupling the sluggish oxygen evolution reaction from overall water splitting, which still needs electricity input. We have realized hydrogen production and water desalination with on-demand electricity output via an electrochemical neutralization chemistry strategy that couples acidic hydrogen evolution and alkaline hydrazine oxidation with ionic exchange. The electrochemical neutralization cells allow efficient use of chemical energy and low-grade heat from the surroundings to output 0.81 kWh electricity per m³ of hydrogen. Cell function can be rapidly switched to electricity output with a high peak power density up to 85.5 mW cm^-2 or spontaneous hydrogen production at a high rate up to 70.1 mol h^-1  m^-2 without breaking cell operation or changing cell configuration. Fast water desalination is simultaneously achieved at a high salt removal rate of 56.1 mol h^-1  m^-2 without an external electricity supply.