Mn-doping and NiFe layered double hydroxide coating: Effective approaches to enhancing the performance of α-Fe2O3 in photoelectrochemical water oxidation

• Two approaches were used simultaneously to improve the PEC water oxidation of α-Fe2O3.
• Doping with Mn enhances the charge separation efficiency of α-Fe2O3.
• Coating α-Fe2O3 with NiFe-LDH improves its charge injection efficiency.
• The amount of NiFe-LDH coating has a significant effect on the performance of α-Fe2O3.

The efficiency of an electrode in photoelectrochemical (PEC) water splitting is determined by the light absorption efficiency, charge separation efficiency, and charge injection efficiency (η = ηabsorption × ηseparation × ηinjection). Here, doping with Mn element and coating with NiFe layered double hydroxide (NiFe-LDH) have been applied to enhance the charge separation efficiency and charge injection efficiency of α-Fe2O3 as a water oxidation catalyst in the PEC water splitting process. The Mn doping improves the charge separation efficiency from 20% to 35% at high potential. The coating amount of NiFe-LDH, which can be controlled by hydrothermal conditions, has a significant effect on the performance of α-Fe2O3. At low precursor concentrations, the formed thin NiFe-LDH has little effect on the light absorption of α-Fe2O3, while NiFe-LDH fabricated at high precursor concentrations forms a thick layer that affects the light absorption of α-Fe2O3. The thin NiFe-LDH layer shifts the onset potential negatively and enhances the charge injection efficiency to 90% at high potential.

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