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The quaternary chalcogenide Cu2NiSnS4 (CNTS) nanoparticles, made up of earth-abundant elements, are one of the most favorable in the family of CMxTS (Mx = Ni, Co, Cd, Fe, Mg, Mn, and Zn) for photoelectrochemical (PEC) hydrogen production due to the lowest resistivity, high absorption coefficient, and tunable band gap for sunlight absorption with suitable band edges. A p-type semiconductor, CNTS, is one of the stable photocathodes in the category of efficient ones. In this theoretical-aided experimental work, we illustrate the photoelectrochemical credibility of CNTS nanomaterials synthesized by a facile hot-injection method with CdS as a photoanode for hydrogen evolution with the interface of an alkaline electrolyte. Using density functional theory simulations, charge density difference, work function, and structural properties were evaluated, suggesting better lattice matching at the CNTS/CdS supercell interface with a lattice mismatch less than 3% along with better charge transfer. An optical band gap of 1.40 eV and a crystallite size of 48 nm were observed for CNTS evaluated. A high short-circuit current density of 6.656 mA cm–2 IPCE for the CNTS/CdS heterojunction was observed to be 14.87% at 505 nm. This promotes the heterojunction to possess minimal chances of material's phase change and hence stability. [ABSTRACT FROM AUTHOR]

Considering the importance of physics and chemistry at material interfaces, we have explored the coupling of multinary chalcogenide semiconductor Cu 2 NiSnS 4 nanoparticles (CNTS NPs) for the first time with the noble metal (Au) to form Au-CNTS nano-heterostructures (NHSs). The Au-CNTS NHSs is synthesized by a simple facile hot injection method. Synergistic experimental and theoretical approaches are employed to characterize the structural, optical, and electrical properties of the Au-CNTS NHSs. The absorption spectra demonstrate enhanced and broadened optical absorption in the ultraviolet-visible-near-infrared (UV-Vis-NIR) region, which is corroborated by cyclic voltammetry (CV) readings. CV measurements show type II staggered band alignment, with a conduction band offset (CBO) of 0.21 and 0.23 eV at the Au-CNTS/CdS and CNTS/CdS interface, respectively. Complementary first-principles density functional theory (DFT) calculations predict the formation of a stable Au-CNTS NHSs, with the Au nanoparticle transferring its electrons to the CNTS. Moreover, our interface analysis using ultrafast transient absorption experiments demonstrate that the Au-CNTS NHSs facilitates efficient transport and separation of photoexcited charge carriers when compared to pristine CNTS. The transient measurements further reveal a plasmonic electronic transfer from the Au nanoparticle to CNTS. Our advanced analysis and findings will prompt investigations into new functional materials and their photo/electrocatalysis and optoelectronic device applications in the future.

Ternary Cu 2 SnS 3 (CTS) is an attractive nontoxic and earth-abundant absorber material with suitable optoelectronic properties for cost-effective photoelectrochemical applications. Herein, we report the synthesis of high-quality CTS nanoparticles (NPs) using a low-cost facile hot injection route, which is a very simple and nontoxic synthesis method. The structural, morphological, optoelectronic, and photoelectrochemical (PEC) properties and heterojunction band alignment of the as-synthesized CTS NPs have been systematically characterized using various state-of-the-art experimental techniques and atomistic first-principles density functional theory (DFT) calculations. The phase-pure CTS NPs confirmed by X-ray diffraction (XRD) and Raman spectroscopy analyses have an optical band gap of 1.1 eV and exhibit a random distribution of uniform spherical particles with size of approximately 15-25 nm as determined from high-resolution transmission electron microscopy (HR-TEM) images. The CTS photocathode exhibits excellent photoelectrochemical properties with PCE of 0.55% (fill factor (FF) = 0.26 and open circuit voltage (Voc) = 0.54 V) and photocurrent density of -3.95 mA/cm 2 under AM 1.5 illumination (100 mW/cm 2 ). Additionally, the PEC activities of CdS and ZnS NPs are investigated as possible photoanodes to create a heterojunction with CTS to enhance the PEC activity. CdS is demonstrated to exhibit a higher current density than ZnS, indicating that it is a better photoanode material to form a heterojunction with CTS. Consistently, we predict a staggered type-II band alignment at the CTS/CdS interface with a small conduction band offset (CBO) of 0.08 eV compared to a straddling type-I band alignment at the CTS/ZnS interface with a CBO of 0.29 eV. The observed small CBO at the type-II band aligned CTS/CdS interface points to efficient charge carrier separation and transport across the interface, which are necessary to achieve enhanced PEC activity. The facile CTS synthesis, PEC measurements, and heterojunction band alignment results provide a promising approach for fabricating next-generation Cu-based light-absorbing materials for efficient photoelectrochemical applications., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)