Significant Improvements on BiVO₄@CoPi Photoanode Solar Water Splitting Performance by Extending Visible-Light Harvesting Capacity and Charge Carrier Transportation

Abstract

Efficient light harvesting and transfer of photogenerated charge carriers between the photoanode and the O2 evolution catalyst are crucial for robust photoelectrochemical (PEC) water splitting. Herein, we present a simple strategy to improve the light harvesting capability and the hole transfer efficiency by anchoring dithiooxamide-derived N, S co-doped carbon nanosheets (NSCN) as a visible-light harvester and polyaniline (PANI) as a hole transfer layer from BiVO4 to CoPi. The resultant BiVO4–NSCN/PANI@CoPi photoanode exhibits the stable photocurrent density of 4.46 mA/cm2 at 1.23 V versus the reversible hydrogen electrode (VRHE) under 1 sun illumination. The applied bias photon-to-current efficiency (ABPE) is measured to be 1.13% at 0.74 VRHE. The photocurrent density and the ABPE are significantly higher than the previous BiVO4 photoanodes. In addition to the high photocurrent density, the photoanode exhibits excellent stability, where the photocurrent density decreases by only 3% over 10 h. Systematic experimental studies reveal that controlled thin layers of NSCN and PANI contribute to efficient light harvesting and charge transfer between BiVO4 and CoPi, resulting in a high photocurrent density and stability. We believe that the proposed approach is effective for the design of efficient and stable photoanodes for PEC water splitting.

Boosting Water Oxidation Performance of BiVO4 Photoanode by Vertically Stacked NiO Nanosheets Coupled with Atomically Dispersed Iridium Sites

“…14–0688), without any additional features due to impurities. The results strongly demonstrate that during the thermal annealing process, BiOI was completely converted into BiVO 4 . Other fabricated photoanodes, BiVO 4 @NiO, BiVO 4 @Ir, and BiVO 4 @NiO–Ir, exhibited diffraction patterns similar to the bare BiVO 4 nanostructures, which indicates that the deposited NiO and Ir single atoms do not alter the crystal structures of the parent BiVO 4 .…”

“…The results strongly demonstrate that during the thermal annealing process, BiOI was completely converted into BiVO 4 . 17 The chemical oxidation states and purity of the fabricated BiVO 4 @NiO−Ir were verified by X-ray photoelectron spectroscopy (XPS) (Figure 5). The XPS survey spectrum (Figure 5(a)) in a scale range of 0−1200 eV clearly shows the presence of elements related to Bi, V, O, Ni, and Ir, which are from BiVO 4 , NiO, and Ir single atoms.…”

“…Both PL and EIS measurements firmly support that the charge carriers' transport improved (thus higher photocurrent density) after coating with NiO− Ir. 15,17 Given that intrinsic surface capacitances of the designed photoelectrodes are approximately the same, electrochemically active surface areas of photoelectrodes were estimated (Figure S10). 53,54 It is evident that the electrochemically active surface area of BiVO 4 @NiO−Ir, which was estimated from the cyclic voltammetry area, is larger than other photoelectrodes.…”

Single-atom catalysts for high-efficiency photocatalytic and photoelectrochemical water splitting: distinctive roles, unique fabrication methods and specific design strategies

“…67–71 On the other hand, in some cases, a so-called light-harvesting unit (LHU) was added into photocatalysts to absorb sunlight in the visible and infrared regions, showing high photocatalytic activity for water splitting. 56,72,73…”

“…[67][68][69][70][71] On the other hand, in some cases, a so-called light-harvesting unit (LHU) was added into photocatalysts to absorb sunlight in the visible and infrared regions, showing high photocatalytic activity for water splitting. 56,72,73 Efficient separation and transfer of photoinduced charge carriers to surface active centers for redox reactions also play a key role in achieving high photocatalytic activity for water splitting. Ineffective charge transfer inside photocatalysts is considered to be a big bottleneck for photocatalytic water splitting due to the possible existence of the backward reaction of water splitting even if the photocatalysts displayed strong light-harvesting capability and enough active surface sites.…”