First-principles study on CuAlTe2 and AgAlTe2 for water splitting

• The electronic structures of AgAlTe2 and CuAlTe2 have been studied.
• The band edge positions of AgAlTe2 straddle the water redox potentials.
• Ga-doping can optimize the band structure of AgAlTe2 for water splitting.

I–III–VI2 chalcopyrite compounds (I = Cu or Ag; III = Al, Ga, or In; VI = S, Se, or Te), especially sulfides and selelides, were studied as the promising photocathodes for water splitting. In this work, tellurides with a proper band gap [i.e. CuAlTe2 (2.06 eV) and AgAlTe2 (2.27 eV)] had been investigated as the photocathode candidates by our first-principles calculations. Our results show that the band edge positions of AgAlTe2 straddle the water redox potentials. In combination with the suitable band gap energy and light carrier effective masses along [001]-direction, AgAlTe2 has the capacity of being a good candidate for water splitting. Moreover, to increase the absorbing ability on visible light, Ga-doping can adjust the band gap of AgAlTe2 to an appropriate value and remain the reasonable band edge positions of AgAlTe2, which is suggested as an effective approach to optimize its electronic structure for water splitting.