Optimizing “Artificial Leaf” Photoanode-Photocathode-Catalyst Interface Systems for Solar Water Splitting

A novel dual photoabsorber interface: perovskite oxynitride (SrNbO 2 N) deposited on silicon (100), and a H 2 ER catalyst photoabsorber interface: (Ni 5 P 4 or Ni 2 P)-silicon, are fabricated. Titanium nitride (TiN) is introduced as a blocking layer between Sr 2 Nb 2 O 7 and Si (100), which produces clean interfaces. During the high temperature ammonolysis step needed to convert Sr 2 Nb 2 O 7 to SrNbO 2 N, it is effective at blocking Nb and Si (but not Sr) migration. A half-cell cathode with the H 2 ER catalyst (Ni 5 P 4 or Ni 2 P)-photoabsorber interface produces H 2 approaching best-in-class overpotentials for films (Ni 5 P 4 : 211mV vs RHE at 10mV/cm 2 ) with a 50mV/decade Tafel slope. Films are atomically smooth, except for surface phosphate that is removed during electrolysis.