Band gap-tunable (CuIn)xZn2(1−x)S2 solid solutions: preparation and efficient photocatalytic hydrogen production from water under visible light without noble metals

Abstract

A series of (CuIn) x Zn 2(1Àx) S 2 solid solutions has been successfully synthesized by a solvothermal approach, and the obtained solid solutions, with a size of about 10 nm, exhibit significant absorption in the visible light region and their band gap can be correspondingly tuned from 2.59 eV to 1.64 eV with an increase of the x value from 0.05 to 0.5, implying that they can be used as visible-light driven photocatalysts. Furthermore, the obtained (CuIn) x Zn 2(1Àx) S 2 solid solutions display highly efficient photocatalytic activities for H 2 evolution from aqueous solutions containing sacrificial reagents (SO 3 2À and S 2À ) under visible light (l > 420 nm) even without noble metal co-catalysts, e.g. (CuIn) 0.2 Zn 1.6 S 2 , with a band gap of 2.10 eV, exhibits the highest photocatalytic activity of 0.984 mmol g À1 h À1 even without a Pt co-catalyst. Further studies reveal that the photocatalytic H 2 evolution of solid solutions depends on their composition as well as the photophysical properties, such as the ability to absorb visible light and the generation and separation of photo-induced electrons and holes.

Colloidal synthesis of wurtzite CuInS2 nanocrystals and their photovoltaic application

“…The group I-III-VI 2 (CuInS 2 , CuInSe 2 , CuIn x Ga 1À x (S,Se) 2 , (CIGSSe)) semiconductor materials which possess excellent optical properties with direct bang gap in the range of 1-1.5 eV and high absorption coefficient of 10 4 -10 5 cm À 1 have attracted a lot of attention because of their wide range of applications, such as, electronic devices-solar cells [1][2][3][4], light emitting diode [5][6][7][8][9], photocatalysis [10][11][12], and bio-label [13,14]. Recently, with the increasingly environmental pollution and intensified energy crisis, solar cells based on I-III-VI 2 semiconductor materials have received more and more attention [15][16][17][18][19][20][21].…”

Efficient photocatalytic H2production using visible-light irradiation and (CuAg)xIn2xZn2(1 − 2x)S2photocatalysts with tunable band gaps

“…The visible-light absorbance of (CuAg) x In 2x Zn 2(1 À 2x) S 2 monotonously increased with increasing x value. According to the Kubelka-Munk function, the band gaps of (CuAg) x In 2x Zn 2(1 À 2x) S 2 can be determined from the plot of (αhν) 2 versus the energy of the excitation light (hν) based on the direct band gap [25], where α is the absorption coefficient (the absorbance in Figure 3a) and hν is the incident photon energy, by extrapolating to zero value [20,52]. These samples had intense absorption bands with steep edges in the visiblelight region, indicating that the visible-light absorption was due to a band gap transition rather than to the transition of impurity energies to the CB of (CuAg) x In 2x Zn 2(1 À 2x) S 2 ; this phenomenon was also observed for metal-ion-doped ZnS photocatalysts [22,25,50,51].…”

“…ZnS-based photocatalysts have small band gaps (<3.0 eV) [20][21][22][23][24], and incorporation of other elements (e.g. Ag + , Cd 2+ , Cu 2+ , In 3+ , and Sn 4+ ) into the structure of ZnS has led to effective visible-light-driven photocatalysts [3,[25][26][27][28][29]. Moreover, the band gaps of many sulfide photocatalysts can be tuned by adjusting their elemental ratios [22,24,30].…”

Colloidal synthesis of CuGaS x Se 2 − x nanoribbons mediated by Cu 1.75 (SSe) nanocrystals as catalysts

“…In recent years, liquid-phase deposition of I-III-VI 2 semiconductors has attracted much attention, with special interest paid to the materials suitable for efficient thin film photovoltaic devices [5][6][7][8][9]. The nanocrystals derived from liquid-phase deposition show merits in facile synthesis, tunable properties, low-cost photovoltaic device cell assembling and high performance [10][11][12]. It has become increasingly facile to precisely control the size, shape, and structure of ternary colloidal semiconductor nanocrystals [13][14][15].…”