Substitutional Mo doping in a Ta₃N₅ photoanode: mitigating native defects through engineering and enhancing...

Area of Science:

• Materials Science
• Photochemistry
• Renewable Energy

Background:

• Tantalum nitride (Ta3N5) is a promising material for solar water splitting due to its bandgap and band edge positions.
• Defective states in Ta3N5, caused by reduced tantalum species, limit its performance by acting as recombination centers.

Purpose of the Study:

• To investigate the effects of Molybdenum (Mo) doping on Ta3N5 to inhibit structural defects and improve photoelectrochemical activity.
• To understand the mechanism of Mo substitution and its impact on the electronic and optical properties of Ta3N5.

Main Methods:

• Combined theoretical calculations and experimental studies were employed.
• Density Functional Theory (DFT) was used to model Mo doping in Ta3N5.
• Photoelectrochemical measurements were conducted to assess performance.

Main Results:

• Mo doping transforms Ta3N5 from an indirect to a direct bandgap semiconductor, reducing the bandgap.
• Mo substitution introduces neutralizing acceptor states, mitigating reduced Ta species and nitrogen vacancies, thus enhancing charge carrier transport.
• Experimental results showed a 4.3-fold increase in photoelectrochemical activity and a 150 mV cathodic shift in onset potential.

Conclusions:

• Substitutional Mo doping effectively suppresses defects in Ta3N5 without inducing lattice strain.
• Mo-doped Ta3N5 exhibits enhanced optical and photoelectrochemical properties, making it a viable candidate for efficient solar fuel production.
• This study highlights the potential of precise doping strategies for advancing photoelectrochemical systems.