Near-Complete Suppression of Surface Recombination in Solar Photoelectrolysis by “Co-Pi” Catalyst-Modified W:BiVO₄

Abstract

The influence of an earth-abundant water oxidation electrocatalyst (Co-Pi) on solar water oxidation by W:BiVO(4) has been studied using photoelectrochemical (PEC) techniques. Modification of W:BiVO(4) photoanode surfaces with Co-Pi has yielded a very large (∼440 mV) cathodic shift in the onset potential for sustained PEC water oxidation at pH 8. PEC experiments with H(2)O(2) as a surrogate substrate have revealed that interfacing Co-Pi with these W:BiVO(4) photoanodes almost completely eliminates losses due to surface electron-hole recombination. The results obtained for W:BiVO(4) are compared with those reported recently for Co-Pi/α-Fe(2)O(3) photoanodes. The low absolute onset potential of ∼310 mV vs RHE achieved with the Co-Pi/W:BiVO(4) combination is promising for overall solar water splitting in low-cost tandem PEC cells, and is encouraging for application of this surface modification strategy to other candidate photoanodes.

Recent Progress in Energy‐Driven Water Splitting

“…The active role of W and Mo facilitated the separation of excited electron‐hole pairs in BiVO 4 , thus leading to the enhanced photocatalytic performance. On the other hand, surface modification with a cocatalyst such as CoPi on BiVO 4 electrode is an effective way to lower the activation energy and decrease the overpotential for water oxidation 182. Particularly, the PEC efficiency was enhanced 15 and 20 folds by CoPi in terms of OER and current generation, respectively 183.…”

Efficient photoelectrochemical hydrogen production from bismuth vanadate-decorated tungsten trioxide helix nanostructures

“…Here we also estimated the charge separation efficiency for our heterojunction system by evaluating its sulphite oxidation performance (J SUL ). It is known that for each single or heterojunction semiconductor, the maximum photocurrent density (J MAX ) is determined by its band gap energy, but the PEC performances are influenced by its light harvesting efficiency (Z LHE ), charge separation efficiency (Z SEP ) and the surface transfer efficiency (Z TRA ) 19,20 . For sulphite oxidation, Z TRA can be considered to be 100% due to its fast oxidation kinetics, resulting in Fig.…”

Photochemical Charge Separation at Particle Interfaces: The n-BiVO4–p-Silicon System

“…The light absorption depth of BiVO 4 can be estimated as 250 nm using the reported absorption coefficient of 40 000 cm −1 at 420 nm. 45 That means a 750 nm thick BiVO 4 film absorbs >95% of the incident super band gap photons. Experimentally, this situation is approached for the 1652 nm thick film in Figure 4a, which gives the greatest photovoltage.…”