Sunlight Selective Photodeposition of CoO_x(OH)_y and NiO_x(OH)_y on Truncated Bipyramidal BiVO₄ for Highly Efficient Photocatalysis

Abstract

Facet-engineered monoclinic scheelite BiVO4 particles decorated with various co-catalysts were successfully synthesized by selective sun light photodeposition of metal or metal oxy(hydroxide) nanoparticles onto the facets of truncated bipyramidal BiVO4 monoclinic crystals co-exposing {010} and {110} facets. X-ray photoelectron spectroscopy, scanning electron microscopy and scanning Auger microscopy revealed that metallic silver (Ag) and cobalt (oxy)hydroxide (CoOx(OH)y) particles were selectively deposited onto the {010} and {110} facets, respectively, regardless of the co-catalyst amount. By contrast, the nickel (oxy)hydroxide (NiOx(OH)y) photodeposition depends on the nickel precursor amount with an unprecedented selectivity for 0.1 wt% NiOx(OH)y/BiVO4 with a preferential deposition onto the {010} facets and the edges between the {110} facets. Moreover, these noble metal-free heterostructures led to remarkable photocatalytic properties for rhodamine B photodecomposition and sacrificial water oxidation reactions. For instance, 0.2 wt% CoOx(OH)y/BiVO4 led to one of the highest oxygen evolution rate, i.e. 1538 mol.h -1 .g -1 , ever described which is ten times higher than that found for bare BiVO4. The selective deposition of cobalt (oxy)hydroxide species onto the more electrondeficient facet of truncated bipyramidal monoclinic BiVO4 particles favors photogenerated charge carrier separation and therefore plays a key role for efficient photochemical oxygen evolution.

Unveiling Carrier Dynamics in Periodic Porous BiVO4 Photocatalyst for Enhanced Solar Water Splitting

“…The O 2 evolution rate for the 3DOM BiVO 4 is ∼660 μmol h –1 g –1 (for 0.05 g of photocatalyst), which is on par with the best performing BiVO 4 photocatalyst (Table S1). − Furthermore, the 3DOM BiVO 4 sample exhibits a higher anodic photocurrent density than the platelike BiVO 4 (Figure b), which also agrees well with the trend of photocatalytic gas evolution activities. Interestingly, a more negative onset potential and a sharper increase of photocurrent density between 0.4 and 0.6 V versus reversible hydrogen electrode (RHE) were observed for the 3DOM BiVO 4 , which is possibly ascribed to their different surface work functions .…”

Transition‐Metal‐Based Cocatalysts for Photocatalytic Water Splitting

“…According to the elemental composition, these reduction cocatalysts can be further classified as elemental metals (e.g., Ni, [ 29 ] Cu, [18b] and CoNi alloy [ 30 ] ), metal sulfides (e.g., MoS 2 , [ 31 ] NiS, [ 32 ] and CoMoS x [ 33 ] ), metal phosphides (e.g., Ni 2 P, [ 34 ] CoP, [ 35 ] and NiFeP [ 36 ] ), metal nitrides (e.g., Ni 3 N [24a] and Co 3 N [ 37 ] ), metal carbides (e.g., Ni 3 C [ 38 ] and Mo 2 C [ 39 ] ), metal borides (e.g., NiB [ 40 ] and NiCoB [ 41 ] ), metal oxides (e.g., NiO [ 42 ] and CuO [ 43 ] ), and metal hydroxides (e.g., Ni(OH) 2 [ 44 ] and Cu(OH) 2 [ 45 ] ) (Figure 1). In comparison, a few transition‐metal‐based cocatalysts are utilized as oxidation cocatalysts, involving the metals (e.g., Co [ 46 ] and Mn [ 47 ] ), oxides (e.g., CoO x [ 48 ] and MnO x [ 49 ] ), hydroxides (e.g., Co(OH) 2 [ 50 ] and Fe(OH) 3 [ 51 ] ), oxyhydroxides (e.g., FeOOH [ 52 ] and CoOOH [ 53 ] ), and phosphates (e.g., Co‐Pi [ 54 ] and CoNi‐Pi [27b] ), also as shown in Figure 1.…”

“…Transition metal hydroxides and oxyhydroxides have strong adsorption and hydrogen bonding interactions toward water molecules, therefore they could be utilized as promising oxidation cocatalysts on semiconductor photocatalysts to improve the photocatalytic water splitting performance. [ 388 ] Up to now, a few metal hydroxides such as cobalt hydroxide, [ 50,371 ] nickel hydroxide, [ 388 ] iron hydroxide, [ 51 ] and bimetal layered hydroxides [ 372–374 ] as well as some metal oxyhydroxides including iron oxyhydroxide, [21a,52,376,389] cobalt oxyhydroxide, [21b,21c,53,375] and nickel oxyhydroxide [ 53 ] have been investigated as cocatalysts for photocatalytic water oxidation. Since these hydroxides and oxyhydroxides have semiconducting properties, when they are supported on the surface of semiconductors, heterojunctions are inclined to be formed to accelerate the separation and transfer of photoinduced holes.…”

“…Furthermore, the oxyhydroxides based on nickel and cobalt components have been developed as cocatalysts as well. For instance, Toupance et al [ 53 ] investigated the cocatalytic performance of CoO x (OH) y and NiO x (OH) y cocatalysts on BiVO 4 in photocatalytic O 2 evolution. They found CoO x (OH) y loaded BiVO 4 showed significantly higher performance for O 2 evolution in contrast that of NiO x (OH) y loaded BiVO 4 , achieving a maximum rate of up to 1538 μmol h −1 g −1 .…”

Cu/CdS/MnOx Nanostructure-Based Photocatalyst for Photocatalytic Hydrogen Evolution

“…are inclined to capture holes, while reduction cocatalysts, containing Ag, Au, Pt, etc., exhibit appetency for electrons. At the same time, the existence of cocatalysts is conducive to accelerate the spatial reaction for the redox process. − Therefore, different cocatalysts can be reasonably designed to achieve the purposes of oxidation and reduction, respectively. Chung et al adopted a hydrothermal method to synthesize Pt-containing TiO 2 samples that demonstrated excellent hydrogen production performance and stability, and Liu and co-workers deposited CoFe-H on BiVO 4 photoanodes which displayed markedly heightened OER kinetics and photocurrent density .…”