Surface Recombination Passivation of the BiVO₄ Photoanode by the Synergistic Effect of the Cobalt/Nickel Sulfide Cocatalyst

Abstract

The photoelectrochemical (PEC) water splitting performance of BiVO4 is limited by its sluggish surface water oxidation kinetics, which could be addressed by surface modification with oxygen evolution catalysts (OECs) as cocatalysts. Here, an ultrathin layer of cobalt/nickel-based sulfide is successfully deposited on the pyramidal BiVO4 photoanode as a cocatalyst to improve its surface kinetics. An increased photocurrent density and negative shift of onset potential are achieved for this BiVO4/cocatalyst composite, with nearly 99% of surface hole injection yield. The kinetic data based on IMPS show that the presence of a cocatalyst brings about a great decrease in surface charge recombination rate from 150 to 22 s–1 at 0.8 V vs RHE, which reveals that the cobalt/nickel sulfide cocatalyst serves as a passivation layer to suppress recombination at surface states and consequently enhance surface water oxidation kinetics.

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

“…From the results, it is clear that an appropriate wt % of Ir single-atom deposition is crucial to obtain a higher photocurrent density. The chopped light LSV curves of all photoanodes exhibited fast and reproducible light-dependent responses (Figure (b)), demonstrating the photoanodes have a quite rapid charge carrier transport nature …”

Promising CoFe-NiOOH Ternary Polymetallic Cocatalyst for BiVO4-Based Photoanodes in Photoelectrochemical Water Splitting

“…Especially, BiVO 4 as a promising, low-cost, and facile synthesis semiconductor-based material has a suitable band gap (∼2.4 eV), which can meet the requirements of oxygen evolution in thermodynamics and requires only a small bias voltage to achieve hydrogen evolution. Therefore, it has been widely favored by researchers. − However, because of the inherent poor carrier separation and migration and slow surface oxygen evolution kinetics, the development of BiVO 4 in PEC systems is greatly restricted. , For these reasons, some modification schemes, such as doping, building heterojunctions, and introducing cocatalysts, have been proposed to improve these shortcomings.…”

“…On this basis, the discovery of binary or polybasic transition metal-based cocatalysts is a step breakthrough. It has been reported that it improves the carrier concentration and conductivity, increases the structural disorder, and obtains better oxygen evolution reaction performance. , It tends to show better photoelectric properties than monobasic cocatalysts, which can be ascribed to the synergistic effect of the multi-metals and makes the band edge shift and adsorption energy change toward a favorable direction. − Typically, binary bimetallic oxides or hydroxides have been widely studied in the field of PEC, for example, Lu et al loaded an ultrathin layer of cobalt/nickel-based sulfide on the surface of BiVO 4 to improve its surface dynamics and achieved a surface hole injection rate of nearly 99% . Chen et al used a simple ligand-controlled oxidation method to load a NiFeOOH-OEC film on the iron oxide photoelectrode and the incident photon-to-current conversion efficiency (IPCE) value of the Fe 2 O 3 /NiFeOOH core shell NAS is 40.7% at 400 nm, which is much higher than that of bare Fe 2 O 3 by 6.1% .…”

“…9−11 However, because of the inherent poor carrier separation and migration and slow surface oxygen evolution kinetics, the development of BiVO 4 in PEC systems is greatly restricted. 12,13 For these reasons, some modification schemes, such as doping, 14 building heterojunctions, 15 and introducing cocatalysts, 16 have been proposed to improve these shortcomings.…”

“…26−28 Typically, binary bimetallic oxides or hydroxides have been widely studied in the field of PEC, for example, Lu et al loaded an ultrathin layer of cobalt/ nickel-based sulfide on the surface of BiVO 4 to improve its surface dynamics and achieved a surface hole injection rate of nearly 99%. 16 Chen et al used a simple ligand-controlled oxidation method to load a NiFeOOH-OEC film on the iron oxide photoelectrode and the incident photon-to-current conversion efficiency (IPCE) value of the Fe 2 O 3 /NiFeOOH core shell NAS is 40.7% at 400 nm, which is much higher than that of bare Fe 2 O 3 by 6.1%. 18 Ternary polymetallic compounds are rarely reported.…”