Electron-rich sulfur sites and dual interfacial bonds in S-scheme heterojunction enable high quantum yield and stable hydrogen production
Sharafat Ali, Sajjad Ali, Shulong Li, Ahmed Ismail, Sher Ali, Muhammad Azzam Ismail, Syed Ul Hasnain Bakhtiar, Fazal Raziq, Mohammad Ziaur Rahman, Liang Qiao
Abstract
The intrinsic strong bonding between sulfur sites and adsorbed hydrogen atoms (S-H ads ) in ZnIn 2 S 4 (ZIS) presents a formidable kinetic bottleneck for H 2 desorption. Additionally, low electron mobility and high recombination of charge carrier synergistically limit its photocatalytic H 2 production efficiency. Here, we engineer sulfur vacancies (Sv) to introduce localized defect states near the Fermi level weakens S-H ads bonds by populating S-H antibonding orbitals and shifting the S 3p center, thus overcoming the H 2 desorption barrier. The rapid electron recombination and low electron in Sv-ZIS have been overcome by integrating it with α-MnO 2 into S-scheme heterojunction. The Density-Functional Theory calculations and experimental reveal that interfacial dual bonds of Mn S and Mn In simultaneously lower electron-transfer barriers and stabilize the catalyst structure. The femtosecond transient absorption spectroscopy has demonstrated a ≈ 6-fold enhanced electron lifetime and a drastic reduction in electron recombination. These result in a ≈ 33 times greater H 2 evolution (16.35 mmol g −1 h −1 ) compared with pristine-ZIS having quantum efficiency of 78 % at 420 nm and a long-term stability endorse by only <1 % decay over 6 months. This article therefore marks a step forward advancement in addressing the longstanding chemical and electronic kinetic challenges in ZIS, and may guide developing highly efficient photocatalysts.