Turning off the “shunt channel” by coating with CoFe layered double hydroxide nanocrystals for efficient photoelectrocatalytic water splitting

Abstract

Building a photoelectrochemical cell to drive water decomposition into hydrogen and oxygen is a feasible way to access clean energy, but the unideal charge transfer path between the cocatalyst and the substrate greatly limits its application. We have developed a facile route for the preparation of a very small and highly crystalline CoFe layered double hydroxide (LDH) cocatalyst on a BiVO₄ electrode through a low temperature chemical bath process. Unlike the conventional successive amorphous CoFe LDH layer coatings achieved through the electrodeposition process, the tiny and crystalline CoFe nanoparticles can close the “shunt channel” between the cocatalyst and the substrate, and the recombination of photogenerated charge caused by back-reaction is inhibited. Also, the interface between crystalline CoFe nanoparticles and BiVO₄ has fewer surface trapped states compared with that of amorphous CoFe LDH layers. The CoFe/BiVO₄ photoanodes showed a desirable photocurrent of 4.3 mA cm⁻² at 1.23 V vs. RHE, and the maximum applied bias photon-to-current efficiency (ABPE) for the crystalline CoFe/BiVO₄ photoanode was calculated to be 1.2% at 1.01 V, consistent with 1.5 times enhancement over that of amorphous CoFe/BiVO₄ and nearly 4 times enhancement over that of BiVO₄.