Enhanced solar water splitting using a TiO2/In2S3 heterojunction coated with NiFe phosphide cocatalyst

A robust photoelectrode is urgently needed for practical solar water splitting. TiO 2 has recognized stability in a wide pH range, but its performance is limited by poor charge separation and low light absorption. In this work, a heterojunction photoelectrode of TiO 2 /In 2 S 3 has been fabricated through a hydrothermal method and coated with bimetallic NiFe phosphide (NiFeP) cocatalyst derived from NiFe Prussian blue analogue through a low temperature phosphidation process. The TiO 2 /In 2 S 3 /NiFeP photoanode delivers a remarkable photocurrent of 3.18 mA cm −2 at 1.23 V vs. RHE, which is 92.17 % of its theoretical photocurrent. Stability testing under AM 1.5G illumination reveals that this photoanode retains 97.67 % of its initial photocurrent after 12 h in 1 M KOH electrolyte without the sacrificial reagent. Moreover, the TiO 2 /In 2 S 3 /NiFeP delivers a superior charge separation efficiency of 92.46 % and a high charge injection efficiency of 92.31 %. Due to the use of narrow bandgap In 2 S 3 , the composite photoanode achieves improved light absorption and efficient charge separation, benefiting from the type-II heterojunction between TiO 2 and In 2 S 3 . The integration of the NiFeP cocatalyst further accelerates charge transfer through the favorable surface states at the semiconductor-electrolyte interface and protects the In 2 S 3 layer from photocorrosion. • Type-II heterojunction TiO 2 /In 2 S 3 photoanode is fabricated and coated with bimetallic NiFe phosphide. • The TiO 2 /In 2 S 3 /NiFeP photoanode achieves a high photocurrent of 3.18 mA cm −2 at 1.23 V RHE . • Remarkable stability of 97.67 % can be observed in KOH electrolyte without the sacrificial reagent. • NiFeP cocatalyst provides the favorable surface states and protects the In 2 S 3 layer from photocorrosion.