Synthesis and Characterization of N-Type CuGaS₂ Nanoparticles and Films for Purpose of Photoelectrocatalytic Water Splitting

Abstract

In this work, n-type CuGaS2 (CGS) nanoparticles were synthesized using an original colloidal method in N-Methylimidazole solvent with GaCl3, Li2S and CuCl as Ga3+, S2− and Cu+ precursors, respectively. After annealing at 600 °C, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy revealed an excess of gallium with a bulk Ga/Cu atomic ratio of 1.01 and a larger value at the surface. The CGS X-ray diffraction pattern is compatible with a chalcopyrite crystalline phase with crystallites size of about 17 nm. UV-visible spectroscopy measurements showed that CGS sample has a direct band gap energy of 2.41 eV. Capacitance measurements, carried out in aqueous 0.5 M KOH on CGS thin film, using electrochemical impedance spectroscopy, confirmed the material n-type conductivity. The Fermi level was found to be −3.93 eV and the majority charge carrier density is 1.93 × 1018 cm−3. The valence band higher energy level and the conduction band lower energy level are −6.31 eV and −3.90 eV, respectively. The energy level diagram of the n-CuGaS2/electrolyte junction suggests that photo-oxidation of OH− species to produce O2 gas would be favorable; however, a small external cathodic bias would be required to generate H2 gas at the platinum counter electrode.

Review on Microreactors for Photo-Electrocatalysis Artificial Photosynthesis Regeneration of Coenzymes

“…At present, there is little research on photo-electric coenzyme regeneration based on microreactors, but the research on water decomposition based on microreactors is expected to promote its future progress. It is found that the oxidative decomposition of water can be realized by PEC [ 159 , 160 ], and holes can be trapped only by water as an electron sacrificial agent in this system [ 161 , 162 ], which effectively reduces the reverse transfer of electrons and helps to realize environmentally friendly, efficient, and economical photo-electric catalytic coenzyme regeneration without additional high-value amines as electron sacrificial agents [ 163 ]. Thakur et al reported that they successfully prepared a paper-based photo-anode (PA) with good flexibility and stability by depositing polypyrrole (PPy) with electrical conductivity, high solar energy absorption, and a suitable cross-band (water oxidation–reduction) on laboratory filter paper, which produced a photocurrent density of about 9.5 mA/cm 2 (1.23 V vs. RHE) in a three-electrode system ( Figure 8 E), and realized efficient and stable photo-electrochemical water decomposition [ 154 ] He et al reported a metal–organic framework with an assembled bifunctional microreactor ( Figure 8 F).…”

“…At present, there is little research on photo tric coenzyme regeneration based on microreactors, but the research on water deco sition based on microreactors is expected to promote its future progress. It is found the oxidative decomposition of water can be realized by PEC [159,160], and holes c trapped only by water as an electron sacrificial agent in this system [161,162], which tively reduces the reverse transfer of electrons and helps to realize environmen friendly, efficient, and economical photo-electric catalytic coenzyme regeneration wi Compared with the conventional system, photo-electric catalytic coenzyme regeneration based on a microreactor has the advantages of easy recovery of catalytic materials, high product purity, and high efficiency. At present, there is little research on photo-electric coenzyme regeneration based on microreactors, but the research on water decomposition based on microreactors is expected to promote its future progress.…”

Snowflake-like Metastable Wurtzite CuGaS2/MoS2 Composite with Superior Electrochemical HER Activity

“…photocatalysis, light-emitting diodes, solar cells, etc., were limited for practical applications owing to their toxicity. This led to a surge in research for finding an alternative environmentally benign semiconductor material with reasonable efficiency compared to that of heavy-metal-based materials. − Recently, I–III–VI 2 ternary semiconductors have attracted much interest due to their narrow band gap, high stability against radiation, low cost, tunable emission wavelength, and high optical absorption coefficient. , Among the various Cu-based ternary chalcogenides, CuGaS 2 is greatly studied as a visible light photocatalyst, a light-emitting diode, and a host material in intermediate-band solar cells due to its low toxicity, good stability, and excellent electrical and optical properties. A direct band gap value of 2.4 eV makes it an efficient catalyst in the field of visible light photocatalyst applications. − Based on the arrangement of cations in the crystal lattice, it is known to exist in three polymorphic states, viz.…”

“… 1 − 3 Recently, I–III–VI 2 ternary semiconductors have attracted much interest due to their narrow band gap, high stability against radiation, low cost, tunable emission wavelength, and high optical absorption coefficient. 4 , 5 Among the various Cu-based ternary chalcogenides, CuGaS 2 is greatly studied as a visible light photocatalyst, a light-emitting diode, and a host material in intermediate-band solar cells due to its low toxicity, good stability, and excellent electrical and optical properties. A direct band gap value of 2.4 eV makes it an efficient catalyst in the field of visible light photocatalyst applications.…”