Ta3N5 Photoanodes Fabricated by Providing NaCl–Na2CO3 Evaporants to Tantalum Substrate Surface under NH3 Atmosphere

Photoelectrochemical (PEC) water splitting is an attractive technique to convert solar energy into chemical fuels of hydrogen and oxygen. Here, we report novel fabrication of Ta3N5 photoanodes using flux method. Layers of Ta3N5 with thickness of several hundred nanometers were grown on the surface of a Ta substrate by using a NaCl–Na2CO3 mixed flux for the crystal growth. The Ta substrate surface was dissolved by the heated and subsequently evaporated particles of NaCl–Na2CO3 in a flow of NH3, and Ta3N5 crystals were formed upon cooling. Analysis of the cross-sectional structure showed that the interface between the Ta3N5 film and the Ta substrate had few voids. In addition, the Ta3N5 film consisted of two layers—a sparse upper layer and a dense lower layer—at a holding temperature of 900 °C, which can be attributed to variations in the evaporation behavior of the flux under different fabrication conditions. When as-synthesized Ta3N5 crystal film was modified using Co–Pi as the co-catalyst, it exhibited a...