Band-Edge Engineering of Ag(InGa)Zn(SeyS1-y) Quantum Dots via Chalcogen Alloying for Cascade Photoanodes Toward Sacrificial-Agent-Free Water Oxidation

TY - JOUR

T1 - Band-Edge Engineering of Ag(InGa)Zn(SeyS1-y) Quantum Dots via Chalcogen Alloying for Cascade Photoanodes Toward Sacrificial-Agent-Free Water Oxidation

AU - Adeniyi, Kayode

AU - Zolotovskaya, Svetlana A.

AU - Adegoke, Oluwasesan

N1 - © 2026 The Authors. Published by American Chemical Society

PY - 2026/7/13

Y1 - 2026/7/13

N2 - Band-edge control is essential for achieving cascade band alignment in multilayered heterostructure photoelectrodes for photoelectrochemical (PEC) water-oxidation relevant operation. Here, we report the synthesis and electronic-structure engineering of colloidal Ag(InGa)Zn(SeyS1−y)2 QDs via Se/S chalcogen alloying (y = 0.0–0.75) to enable deterministic band-edge tuning and rational cascade heterojunction design. Increasing the Se content narrows the optical band gap from 2.22 to 1.79 eV and selectively upshifts the valence-band maximum (VBM) with minimal perturbation of the conduction band edge. This trend is supported by density functional theory (DFT) and projected density of state (PDOS) analyses, which reveal increased Se p-orbital near the VBM. Using the most photoelectrochemically active alloyed QD composition (y = 0.35), we fabricated a TiO2/Ag(InGa)Zn(SeyS1−y)2 QDs/ZnS/NiFe-LDH photoanode in which an ultrathin ZnS passivation layer suppresses surface trap-mediated recombination and a nickel-iron layered double hydroxide (NiFe-LDH) overlayer promotes hole extraction, establishing a stepwise Type-II cascade heterojunction. Under sacrificial-agent-free conditions in 0.1 M borate buffer (pH 9.0), the photoanode achieved a photocurrent density of 1.65 mA cm−2 at 1.0 V vs RHE under broadband LED illumination conditions. Two-electrode measurements further showed that the photoanode||Pt cell produced a photocurrent response of 2.8 mA cm−2 over a broad cell-voltage window and retained 77.6% of its initial current after 53 h under the same fixed broadband LED measurement conditions used in this study. This work demonstrates that chalcogen alloying is a rational strategy for designing multinary QD-based cascade photoanodes with improved water-oxidation-relevant PEC response under the investigated conditions.

AB - Band-edge control is essential for achieving cascade band alignment in multilayered heterostructure photoelectrodes for photoelectrochemical (PEC) water-oxidation relevant operation. Here, we report the synthesis and electronic-structure engineering of colloidal Ag(InGa)Zn(SeyS1−y)2 QDs via Se/S chalcogen alloying (y = 0.0–0.75) to enable deterministic band-edge tuning and rational cascade heterojunction design. Increasing the Se content narrows the optical band gap from 2.22 to 1.79 eV and selectively upshifts the valence-band maximum (VBM) with minimal perturbation of the conduction band edge. This trend is supported by density functional theory (DFT) and projected density of state (PDOS) analyses, which reveal increased Se p-orbital near the VBM. Using the most photoelectrochemically active alloyed QD composition (y = 0.35), we fabricated a TiO2/Ag(InGa)Zn(SeyS1−y)2 QDs/ZnS/NiFe-LDH photoanode in which an ultrathin ZnS passivation layer suppresses surface trap-mediated recombination and a nickel-iron layered double hydroxide (NiFe-LDH) overlayer promotes hole extraction, establishing a stepwise Type-II cascade heterojunction. Under sacrificial-agent-free conditions in 0.1 M borate buffer (pH 9.0), the photoanode achieved a photocurrent density of 1.65 mA cm−2 at 1.0 V vs RHE under broadband LED illumination conditions. Two-electrode measurements further showed that the photoanode||Pt cell produced a photocurrent response of 2.8 mA cm−2 over a broad cell-voltage window and retained 77.6% of its initial current after 53 h under the same fixed broadband LED measurement conditions used in this study. This work demonstrates that chalcogen alloying is a rational strategy for designing multinary QD-based cascade photoanodes with improved water-oxidation-relevant PEC response under the investigated conditions.

KW - chalcogen alloying

KW - multinary quantum dots,

KW - band-edge engineering

KW - cascade heterojunction

KW - TiO2/Ag(InGa)Zn(SeyS1−y)2/ZnS/NiFe-LDH photoanode

KW - photoelectrochemical water oxidation

KW - sacrificial-agent-free PEC

KW - TiO /Ag(InGa)Zn(Se S ) /ZnS/NiFe-LDH photoanode

KW - multinary quantum dots

UR - https://www.scopus.com/pages/publications/105045126706

U2 - 10.1021/acsaem.6c00218

DO - 10.1021/acsaem.6c00218

M3 - Article

SN - 2574-0962

VL - 9

SP - 8015−8030

JO - ACS Applied Energy Materials

JF - ACS Applied Energy Materials

IS - 13

ER -