A Sustainable Strategy for the Synthesis of Pyrochlore H 4 Nb 2 O 7 Hollow Microspheres as Photocatalysts for Overall Water Splitting

A facile and green process was developed for the synthesis of pyrochlore H 4 Nb 2 O 7 hollow microspheres by using hydrothermal treatment of Sn 2 Nb 2 O 7 hollow microspheres in aqueous 2  m HCl at 100–180 °C. The facile transformation of Sn 2 Nb 2 O 7 into H 4 Nb 2 O 7 is facilitated by the intrinsic ion‐exchange capability of Sn 2 Nb 2 O 7 . The resulting H 4 Nb 2 O 7 hollow microspheres (diameter 1–2 μm, shell thickness 100–200 nm) displayed excellent photocatalytic performance for overall water splitting under UV irradiation, affording H 2 and O 2 evolution rates of 240 and 116 μmol h −1  g −1 , respectively. Following decoration with 0.5 wt % Pt, the H 4 Nb 2 O 7 hollow microspheres demonstrated remarkably high H 2 and O 2 evolution rates of 1240 and 600 μmol h −1  g −1 , respectively. To our knowledge, this work is the first reported study examining the photocatalytic performance of H 4 Nb 2 O 7 for water splitting. The hydrothermal synthesis method described here is also applicable to the synthesis of pyrochlore H 4 Ta 2 O 7 from Sn 2 Ta 2 O 7 , highlighting the versatility of the approach.