Non-spontaneous synthetic pathways for anisotropic metal chalcogenides with phase junctions and stacking faults for enhanced photo electrochemical performance

In a breakthrough for photoelectrochemical catalyst design is minimizing carrier recombination. We have developed advanced phase junction solid nanostructures like CdS, CdSe, ZnS and ZnSe through Kirkendall effect driven by cation exchange (CE) from anisotropic metal nanoparticles. The CE reaction produces unfeasible solid crystal structures specifically the CdS and ZnS display alternating sphalerite and wurtzite phases with stacking faults. On the contrary, CdSe and ZnSe have grain boundaries with sphalerite and wurtzite phase junctions. By tracking intermediate solid nanostructures, we observed that the initial hexagonal phase transformed into a cubic phase, with the product retaining the morphology of the template due to their similar sublattices. Comprehensive carrier transport analysis such as transient decay times (τ) and photoluminescence spectra confirmed that improved charge separation compared with monophase. Sphalerite and wurtzite junction forms the heterojunction because both have different work functions, where type II charge transfer happen. The plate-like phase junction CdS achieved a remarkable 0.9 mA cm⁻² photocurrent density at 1.23 V vs RHE and an applied bias photon-to-current efficiency reached 1.1 %, outperforming standard monophase CdS. Photoluminescence spectra confirmed ZnS works under visible light due to the stacking faults. This novel, single-step method for phase junction and stacking faults catalysts could revolutionize energy conversion technologies, offering unprecedented control over catalyst morphology.