Synthesis of robust S-O covalent-bonded In2S3/α-Fe2O3 nanorod arrays heterojunction with a tailored heat treatment strategy for enhanced photoelectrochemical water splitting

A robust S-O covalent-bonded In 2 S 3 /α-Fe 2 O 3 nanorod arrays heterojunction were successfully synthesized via a modified heat treatment strategy. The resulting photoanode exhibits an exceptional photocurrent density of 2.65 mA cm −2 at 1.23 V vs. RHE, achieving a 235 % enhancement compared to robust bare α-Fe 2 O 3 (1.13 mA cm −2 at 1.23 V vs. RHE). To our knowledge, this represents the highest photocurrent density among all reported In 2 S 3 /α-Fe 2 O 3 systems. Moreover, the photoanode demonstrates excellent stability, maintaining over 95 % of its initial performance over 3 h in alkaline electrolyte. The outstanding PEC performances of robust S-O bonded In 2 S 3 /α-Fe 2 O 3 photoanode originates from a synergistic effect of the following aspects: (i) Locking the morphology of FeOOH nanorod array precursor through the improved thermal annealing method decreases charge-carrier recombination; (ⅰi) Forming atomic-level S-O covalent bonds provide direct charge-transfer pathways, thereby enhancing carrier lifetime and reducing interfacial resistance; (iii) Constructing a type-II heterojunction establishes a strong internal electric field that provides a large driving force for the rapid migration of photogenerated charges; and (iv) Loading In 2 S 3 efficiently passivates surface defects and promotes hole injection. • A robust S-O covalent-bonded In 2 S 3 /α-Fe 2 O 3 nanorod arrays heterojunction were successfully synthesized via a modified heat treatment strategy. • This approach facilitates the formation of atomic-level S-O covalent bonds at the In 2 S 3 /α-Fe 2 O 3 interface and simultaneously prevents structural collapse, shrinkage, and coalescence during the phase transition from as-prepared FeOOH nanorods to α-Fe 2 O 3 . • The In 2 S 3 /α-Fe 2 O 3 photoanode exhibits exceptional PEC performances compared to bare α-Fe 2 O 3 , and it achieves the highest photocurrent density among all reported In 2 S 3 /α-Fe 2 O 3 systems. • The outstanding PEC performances of robust S-O bonded In 2 S 3 /α-Fe 2 O 3 photoanode originates from a synergistic effect of S-O covalent bonds, a type-II heterojunction, and the loaded In 2 S 3 .