Anti-photocorrosive photoanode with RGO/PdS as hole extraction layer

Abstract

Photoelectrochemical (PEC) hydrogen production is of great interest as an ideal avenue towards clean and renewable energy. However, the instability and low energy conversion efficiency of photoanodes hinder their practical applications. Here we address these issues by introducing a hole extraction layer (HEL) which could rapidly transfer and consume photogenerated holes. The HEL is constructed by reduced graphene oxide (RGO) and other cocatalysts that enable rapid transfer and subsequent consumption of holes, respectively. Specifically, we showcase a high-stability photoanode composed of CdSeTe nanowires (CST NWs) and RGO/ PdS nanoparticles (PdS NPs) based HEL. The photoanode achieves excellent photocorrosion resistance, which allows stable hydrogen evolution for > 2 h at 0.5 V RHE .

Band Structure Engineering toward Low-Onset-Potential Photoelectrochemical Hydrogen Production

“…The existence of elemental tellurium causes the XRD diffraction peak of CdSe to shift to lower 2θ values. 17,37 High-resolution transmission electron microscopy (HRTEM) images of CST and CST@CS NWs showed lattice spacings of 0.369 and 0.355 nm, which we attributed to the (100) plane of wurtzite-phase CdSe and the (100) plane of wurtzite-phase CdS, respectively (see Figures S7a and S8a in the Supporting Information). Besides, the energy dispersion spectra (EDS) and EDS elemental mapping images of CST nanowires and CST@CS core-shell nanostructures revealed that both elemental cadmium and selenium are uniformly distributed in the CST NWs, while the elemental tellurium is concentrated in the core of the CST NWs, and elemental sulfur is present only in the CdS shell (see Figures S7b−d, S8b, S8c, and S9a in the Supporting Information).…”

“…The optical band gaps of CST, CSST-0.5, CSST-1.0, and CSST-2.0 are 1.51, 2.06, 2.26, and 2.39 eV, respectively. Compared with individual CST NWs, the introduction of elemental sulfur enlarges the We then calculated the work function Φ, 17,38 which is defined as the relative energy between the vacuum level and the Fermi level:…”

“…Compared with other photoanodes, the steadystate photocurrent density of CSST-1.0 photoanode reaches 3.3 mA cm −2 , which is the highest photocurrent value. Since the separation, transfer, and consumption rate of photogenerated carriers in the photoanode all have an important impact on the V onset of the photoanodic current, we further analyzed the carrier transfer process of different photoanodes by electrochemical impedance spectroscopy (EIS), 17 which was performed using a frequency interval of 10 5 −0.1 Hz and an amplitude of 10 mV at a bias potential of 1.0 V RHE . As shown in Figure S25 in the Supporting Information, the semicircle of the CSST-1.0 photoanode has a smaller diameter, which indicates that it has a lower charge-transfer resistance (R ct ) than other photoanodes.…”

“…Numerous semiconductor materials have been used for PEC catalysis, after the pioneering work of Fujishima and Honda. ,− Although great efforts have been devoted to expanding the light absorption range of the photoelectrode to achieve more-efficient solar energy utilization, , however, under a certain bias, excessively low photocarrier separation and reaction efficiency, as well as low photovoltage, led to the high V onset of the photoelectrode, thereby limiting the further improvement of photocurrent and energy conversion efficiency during PEC H 2 production. ,− Effective attempts to negatively shift the V onset can be divided into two categories: one is to reduce the overpotential of the anodic reaction involving photogenerated holes by loading a co-catalyst; the other is to increase the V ph of the photoelectrode by loading other semiconductor materials or using other methods that modulate the energy band structure. ,− …”

Engineering the heterogeneous interfaces of inverse opals to boost charge transfer for efficient solar water splitting

“…Attempts have been made to deposit different photocatalytic components on the ''host'' to build various interfacial heterojunctions including type I heterojunctions, Schottkey junctions, and Ohmic junctions. These can promote photo-induced charge separation and transportation [17][18][19][20]. Some excellent nanostructures can be found in the literature with considerable improvement for PEC performance, such as CdS nanorod@SnO 2 nanobowl [21], Fe 2 O 3 nanorod@nanobowl [22], 3D g-C 3 N 4 /Ni(OH) 2 [23], WO 3 / BiVO 4 /Co-Pi inverse opal [24], and fluorine-doped tin oxide (FTO)/FTO-nanocrystal/TiO 2 inverse opal [25].…”