CuInS₂ Nanosheet Arrays with a MoS₂ Heterojunction as a Photocathode for PEC Water Splitting

Abstract

Developing cost-effective noble metal-free co-catalysts as alternatives to platinum group metals is an impeccable strategy to enhance photoelectrochemical (PEC) water splitting. In this report, we successfully fabricated CuInS2 nanosheet array-based photocathode modified with CdS and co-catalyst MoS2 in a green approach to improve water splitting under solar irradiation. The visible light absorption of the modified hybrid photocathode (CIS/CdS/MoS2) was significantly enhanced due to introducing CdS and MoS2. Photoluminescence, impedance spectroscopy, and Mott–Schottky analysis depicted improved separation of excited electron–hole pairs, minimized resistance of charge transfer, and increased excited-state charge carrier concentration, resulting in increased photocurrent. Typical results indicated that composite photoelectrodes delivered higher photocurrent (−1.75 mA/cm2 at 0 V vs RHE) and HC-STH conversion efficiency (0.42% at 0.49 V vs RHE) than those of CIS and CIS/CdS photoelectrodes. This improved PEC performance is accredited to the synergetic impact of CdS in charge generation and transfer and MoS2 as a cocatalyst with active surface sites for proton reduction. This study not only reveals the promising nature of CuInS2-based light absorber photocathodes for solar energy utilization but also recommends the use of MoS2 as a cocatalyst for the proton reduction reactions for widespread applications in solar to hydrogen conversion.

Exploring CuBi2O4 as a Promising Photocathode Material for PEC Water Splitting

“…The high-resolution deconvoluted XPS of Bi 4f (Figure b) shows two peaks at 158.7 and 164.0 eV, corresponding to Bi 4f 5/2 and Bi 4f 7/2 , respectively, which are typical of Bi 3+ species. Figure c shows the XPS spectra of Cu 2p with the featured binding energies of 934.1 and 954.0 eV corresponding to Cu 2p 3/2 and Cu 2p 1/2 respectively . The asymmetric profile of O 1s can be split into two symmetrical peaks at 529.6 and 531.8 eV (Figure d), indicating lattice oxygen in CBO and chemisorbed oxygen (OH) on the surface, respectively .…”

Photoelectrochemical properties of p-type CuBi2O4 prepared by spray pyrolysis of carbon-free precursor aqueous solution combined with post-annealing treatment

“…34,35 Among them, the CuBi 2 O 4 (CBO) material can be recognized as one of the promising candidates for the photoelectrode material for the PEC HER involving CO 2 reduction. [36][37][38][39][40][41][42][43][44][45][46][47][48] CBO has a tetragonal crystal structure and consists of stacks of square planar Cu(II)O 4 groups linked to distorted trigonal Bi(III)O 6 polyhedral groups. 34 The bandgap (E g ) energy of the CBO material has been reported to be 1.5-1.8 eV (adsorption edge wavelength up to 830 nm), 37,38,42,44 which leads to a theoretical STH energy conversion efficiency limit of B24% at an external quantum efficiency (EQE) of 100%.…”

“…These light-absorption features, theoretically expected PEC performances, and an energy level alignment with the standard redox potential of the HER have promoted advanced research for CBO-based photocathodes involving a PEC cell for nonbiased overall water splitting. 36,[48][49][50][51] Wang et al have reported that the CBO-based photoelectrode prepared through a spray pyrolysis method produces a photocurrent density of À2.0 mA cm À2 at 0.6 V RHE in the presence of an H 2 O 2 sacrificial reagent. 41 In addition, À2.66 mA cm À2 at 0.6 V RHE generated by the optimized CBO photoelectrodes has been established by Xu et al 47 Non-biased overall water splitting by a PEC cell with a combination of photoanodes for the OER such as TiO 2 , BiVO 4 , and ZnIn 2 S 4 has been investigated, but typically exhibits an STH energy conversion efficiency of less than 1.0%.…”

“…41 In addition, À2.66 mA cm À2 at 0.6 V RHE generated by the optimized CBO photoelectrodes has been established by Xu et al 47 Non-biased overall water splitting by a PEC cell with a combination of photoanodes for the OER such as TiO 2 , BiVO 4 , and ZnIn 2 S 4 has been investigated, but typically exhibits an STH energy conversion efficiency of less than 1.0%. 36,[48][49][50][51] Further development of efficient CBO-based photoelectrodes applicable to PEC cells is in demand.…”

“…The CBO-based photoelectrode is typically processed by heating the CBO precursor compounds such as a Cu/Bi complex deposited on the conductive substrates (e.g., F-doped tin oxide coated glass (FTO) and Au) in air. [35][36][37][38][39] CBO precursor compounds have been prepared on the substrates by deposition of the precursor solution using wet processes such as electrodeposition, [36][37][38][39]49,52 drop-casting methods, 36,44,45,48,50 spin-coating methods, 46,47 and spray pyrolysis methods. [40][41][42][43]51,53 Concerning the wet process to prepare CBO-based photocathodes, most of the precursor solution is based on nonaqueous organic solvents (e.g., ethanol and dimethyl sulfoxide) and acetic acid with organic additives (e.g., polyethylene glycol (PEG) and triethyl orthoformate (TEOF)) to dissolve and stabilize the Cu and Bi complex in the solvent.…”