File Name : fig.s1.tif

Caption : figure s1. eds elemental mapping images of a cross-section of the ta3n5/ta sample. the scale bars are 500 nm. a) bse image, b) n k series, c) o k series, d) ta k series. 

File Name : fig.s2.tif

Caption : figure s2. ftir spectra of the products in the quartz tube after reaction. the absorption peaks were assigned to gaseous hcl species.

File Name : fig.s3.tif

Caption : figure s3. left: xrd patterns of (a) ta plate and the samples prepared by reaction of ta plate and nh4cl powder in vacuo at (b) 1053 and (c) 703-1053 k. ta3n5 peaks are indexed. asterisks represent the tanx signals. right: the temperature programs for preparation of sample (b) and (c).

File Name : fig.s4.tif

Caption : figure s4. current-potential curves for (a) pristine ta3n5, (b) co(oh)x/ta3n5 and (c) ni(oh)x/co(oh)x/ta3n5 photoanodes under am 1.5g simulated solar light in 0.5 m na2b4o7 aqueous solution (ph = 13). the ta3n5 photoanode was prepared with the temperature program of 703-1053 k.