General In Situ Photoactivation Route with IPCE over 80% toward CdS Photoanodes for Photoelectrochemical Applications

Abstract

Cost‐effective photoanodes with remarkable electronic properties are highly demanded for practical photoelectrochemical (PEC) water splitting. The ability to manipulate the surface carrier separation and recombination is pivotal for achieving high PEC performance for water splitting. Here, a facile and economical approach is reported for substantially improving the surface charge separation property of CdS photoanodes through in situ photoactivation, which significantly reduces surface charge recombination through the formation of thiosulfate ion which is favorable to the transfer of photogenerated holes and a uniform nanoporous morphology via the dissolving Cd2+ with phosphate ions on the surface of CdS. The resulting CdS electrodes through scalable particle transfer method exhibit nearly tripled photocurrents, with an incident‐photon‐to‐current conversion efficiency (IPCE) at 480 nm exceeding 80% at 0.6 V versus reversible hydrogen electrode (RHE). And the CdS thin films prepared from chemical bath deposition display quadrupled photocurrents after the stir and PEC activation, with an IPCE of 91.7% at 455 nm and 0.6 V versus RHE. With the suppression of photocorrosion in alkaline borate buffer, the activated photoanodes show great stability for solar hydrogen production at the sacrifice of sulfite. This work brings insights into the design of nanoporous metal sulfide semiconductors for solar water splitting.

Recent research progress on operational stability of metal oxide/sulfide photoanodes in photoelectrochemical cells

“…Notably, most semiconductor materials may react with surface-photogenerated holes on the photoanode or with the electrolyte under the action of the PEC test, resulting in material change. Taking CdS as an example, some CdO will be produced on the surface after PEC testing in a neutral or alkaline electrolyte [56]. Although the nanotopography of the photoanode is well maintained at this time, its composition will be changed, which will inevitably lead to a decrease in J for the photoanode.…”

“…CdS is a typical IIB-VIA semiconductor catalyst material with a narrow Eg (2.42 eV) and a suitable energy band position for PEC water splitting and with good photocatalytic ability [56].…”

Cocatalysts‐Photoanode Interface in Photoelectrochemical Water Splitting: Understanding and Insights

“…XPS is a method for analyzing material surfaces and is used to characterize the content of and obtain considerable chemical information about surface elements according to the intensity and movement of XPS peaks, such as the formation of chemical bonds and change in the electronic structure. [117][118][119][120] Because the formation of chemical bonds can improve the interfacial transport of carriers, XPS spectra can provide a wealth of information about relevant chemical bonds and should be carefully studied. For example, Meng et al [59] used XPS to explain interfacial Co-O-V chemical bonds.…”

“…[ 128 ] According to the PEC principle, an ultramicroelectrode is immersed in an electrolyte as a working probe, the photoanode material is scanned in three dimensions, and the photoanode shape and properties are determined by analyzing the current change on the probe surface. [ 118 ] The PEC current generated by the oxidation or reduction of substances in the microarea can be measured, and the interfacial charge transfer can be characterized based on the positive and negative current feedbacks. As shown in Figure 3g–i, under light and dark conditions, different photoanodes exhibit different probe proximity curves.…”

Optoelectronic materials utilizing hot excitons or hot carriers: from mechanism to applications

“…The photocurrent spectrum can be further converted into an IPCE spectrum, which reflects the photoelectric conversion efficiency of the device. 65 In formula (22), J sc is the current density and P is the incident light power.…”