A New Solar Carbon Capture Process: Solar Thermal Electrochemical Photo (STEP) Carbon Capture

Abstract

The first experimental evidence of a new solar process, combining electronic and chemical pathways, to isolate CO2 (carbon capture) is presented. This solar thermal electrochemical photo (STEP) process is a synergy of solid-state and solar thermal processes, and is fundamentally capable of converting more solar energy than photovoltaic or solar thermal processes alone. Here, CO2 is captured using a 750−950 °C electrolysis cell powered by a full spectrum solar simulator in a single step. The process uses the full spectrum; solar thermal energy decreases the energy required for carbon capture, while visible sunlight generates electronic charge to drive the electrolysis. CO2 can be captured from 34% to over 50% solar energy efficiency (depending on the level of solar heat inclusion), as solid carbon and stored, or used as carbon monoxide to be available for a feedstock to synthesize (with STEP generated hydrogen) solar diesel fuel, synthetic jet fuel, or chemical production.

CO2 gas decomposition to carbon by electro-reduction in molten salts

“…This experimental paper will report the validity of these reactions except for Eq.(7). Another mechanism is carbonate formation in molten salt [13][14][15][16][17][18][19]. CO 2 gas dissolves as the carbonate ions (Eq.…”

Sustainable Electrochemical Synthesis of Large Grain- or Catalyst-Sized Iron

“…The electrolysis potential is measured as the voltage between the anode and the cathode at constant current. We have previously reported on STEP cathode or oxygen anode potentials in a variety of molten carbonates [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] During electrolysis, the iron product accumulates at the cathode, which is subsequently removed and cooled. Details of STEP electrolysis are provided in references [5][6][7][8].…”

“…The general solar thermal electrochemical process (STEP) of sunlight to decrease (endogenic) electrolysis potentials leads to high solar energy conversion efficiencies [6][7][8][9][10][11]. A variety of other STEP electrolyses have been demonstrated to decrease CO 2 including the production of cement, ammonia, fuels, and carbon for the direct removal of atmospheric or smokestack carbon dioxide [10][11][12][13][14][15][16][17][18][19][20]. Fundamental, electrochemical, and impurity effects on STEP iron have been investigated [8], and the general effects of alkali earth and hydroxide on STEP processes in molten carbonates have been reported [14][15][16][17][18][19][20].…”

“…A variety of other STEP electrolyses have been demonstrated to decrease CO 2 including the production of cement, ammonia, fuels, and carbon for the direct removal of atmospheric or smokestack carbon dioxide [10][11][12][13][14][15][16][17][18][19][20]. Fundamental, electrochemical, and impurity effects on STEP iron have been investigated [8], and the general effects of alkali earth and hydroxide on STEP processes in molten carbonates have been reported [14][15][16][17][18][19][20]. The fundamental increase in solar electrolysis efficiency with the use of solar thermal has been analyzed for CO 2 and H 2 O splitting theoretically [10][11][12] and experimentally [13][14][15] and the fundamental endogenic decrease in electrochemical potential with the increasing temperature demonstrated for a number of STEP processes [10][11][12][13][14][15][16][17][18][19][20].…”

“…Fundamental, electrochemical, and impurity effects on STEP iron have been investigated [8], and the general effects of alkali earth and hydroxide on STEP processes in molten carbonates have been reported [14][15][16][17][18][19][20]. The fundamental increase in solar electrolysis efficiency with the use of solar thermal has been analyzed for CO 2 and H 2 O splitting theoretically [10][11][12] and experimentally [13][14][15] and the fundamental endogenic decrease in electrochemical potential with the increasing temperature demonstrated for a number of STEP processes [10][11][12][13][14][15][16][17][18][19][20]. The requisite solar thermal heating for any given process will depend on the current density, which controls the overpotential and the net difference between the thermoneutral potential and the applied electrolysis potential.…”