• Energy Research

ABSTRACTThe conventional steelmaking process emits 1.8 tons of CO2 to produce 1 ton of crude steel, making the steel industry the world's largest emitting manufacturing sector. Here, we propose and demonstrate a renewable route based on electrified carbon cycling, which significantly reduces CO2 emission by 83%. The critical step of the route involves electrochemical CO2 reduction (CO2RR) to produce CO‐rich syngas, which reduces iron ore into metallic iron (FexOy‐to‐Fe), effectively closing the carbon cycling. A technoeconomic analysis (TEA) reveals that the energy efficiency of this novel process is dependent on the operating parameters of CO2RR, with optimal efficiency occurring at the current density range of 150‐200 mA cm−2. As a proof‐of‐concept study, sulfur vacancy (VS)‐engineered Ag3CuS2 was developed as a high‐performance CO2RR electrocatalyst. This catalyst yields a CO‐rich syngas at a high Faradaic efficiency (FE) close to 100% at a cell voltage of 2.5 V. The CO2RR‐produced syngas effectively reduced iron oxide into metallic iron. The implementation of electrified carbon cycling significantly increases the utilization of electricity in steel production, reaching 88.7%. This research describes a sustainable way to reshape the ironmaking process and ultimately neutralize the steel industry.

Sn- or Ge-doped hematite thin films were fabricated by annealing alloyed films for the purpose of photoelectrochemical (PEC) water splitting. The alloyed films were deposited on FTO glass by magnetron sputtering and their compositions were controlled by the target. The morphology, crystalline structure, optical properties, and photocatalytic activities have been investigated. The SEM observation showed that uniform, large area arrays of nanoflakes formed after thermal oxidation. The incorporation of doping elements into the hematite structure was confirmed by XRD. The photocurrent density-voltage characterization illustrated that the nanoflake films of Sn-doped hematite exhibited high PEC performance and the Sn concentration was optimized about 5%. The dopedGe4+ions were proposed to occupy the empty octahedral holes and their effect on PEC performance of hematite is smaller than that of tin ions.

Abstract The limited conductivity in hematite has been currently considered as a critical bottleneck in improving the efficiency of solar-driven water oxidation. Here we shed light on the improvement of carrier conductivity by combing orientation control and transition metal doping. To rule out the influence of surface facets of hematite when adjusting the film orientation, the hematite photoanode films were fabricated by assembling the spherical particles with single crystalline nature. The doped hematite particles were aligned with (001) plane normal to the substrate by a magnetic field (MF) during the drop-casting process. A considerable improvement in photocurrent density was resulted from the orientation control, which is due to the increased carrier density from Sn doping and efficient charge transportation in the (001) plane observed through electrochemical impedance spectra.