Bismuth Vanadate (BiVO4) has been actively researched upon over the last couple of years as a potential photoanode for water splitting owing to its near ideal band gap of 2.4eV, high absorption coefficient and stability across a wide pH range(between 3 and 11). Highly efficient solar to hydrogen conversion efficiency of 4.9% has been demonstrated for tandem devices consisting of a BiVO4 photoanode coupled to a double-junction a-Si solar cell. Unfortunately, the carrier separation efficiency of these photoanodes was ~ 65% at 1.23V(RHE). In addition, the processing required to make these photoanodes is extremely time consuming requiring 20 sequential heating and deposition cycles.This work demonstrates a simple technique to deposit 200nm thick, Mo doped, porous BiVO4 films in a single deposition cycle. In addition, grazing incidence XRD reveals the presence of a preferred orientation of the (040) plane which has been shown previously in single crystals to have a higher catalytic activity towards oxygen evolution as well as a lower effective electron mass. These electrodes demonstrate a record 97% charge separation efficiency at 1.23V(RHE) in addition to a high separation efficiency (~80%) at low bias (0.6V). Such textured photoelectrode designs could be used to eventually realize the maximum possible hydrogen conversion efficiency in BiVO4 photoanodes.

Achieving unity charge separation in textured nanostructured Mo:BiVO4 photoelectrodes for solar fuels

248th National Meeting (2014)

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