Preparation of heterometallic CoNi-MOFs-modified BiVO4: a steady photoanode for improved performance in photoelectrochemical water splitting

[Display omitted] •Heterometallic CoNi-MOFs was formed through hydrothermal synthesis method to improve the performance of BiVO4.•Experiments show the Co2+ can increase the photocurrent density while the Ni2+ can decrease the onset potential.•Composite materials have excellent stability as well as high performance. In this work, an efficient nanoporous BiVO4 composite photoelectrode with high photocurrent and low onset potential for photoelectrochemical water splitting is achieved through modification of BiVO4 with a stable heterometallic CoNi-MOF layer. Compared with pristine BiVO4 anode, the formation of CoNi-MOFs/BiVO4 increases the photocurrent density by about 260 %. In addition, the CoNi-MOFs/BiVO4 photoanode is of greater steadiness for water oxidation, without insignificant activity attenuation within 3 reaction hours at 1.23 V vs. RHE. It is postulated that bimetal-organic framework CoNi-MOFs could supply more open sites which account for the impressively enhanced PEC performance of BiVO4 photoanodes toward water splitting under illumination. The results demonstrate a new method to fabricate dual metal nanoparallelepiped-like MOF for steady hydrolysis photoanode material.