Interatomic interaction of 2D crumpled V2O5 nanosheets layered with Ni-MOF as a bifunctional electrocatalyst for overall water splitting and supercapacitor applications

Herein, we have synthesized a highly efficient and economical noble metal-free catalyst via a novel combination of V2O5 nanosheets and Ni MOF. The critical points of this study are (i) achieving a 2D layer structured crumpled V2O5 nanosheets without excessive stacking/aggregation using freeze drying method, (ii) decorating Ni-MOF over the crumpled V2O5 nanosheets to attain an excellent homogeneity and (iii) developing a V2O5 based novel and bifunctional electrocatalyst for overall water splitting and supercapacitor applications. Forming a well-interlinked morphological structure accompanies a homogeneous dispersion of Ni MOF over the V2O5 nanosheet. Among the multiple compositions, the NiV4 exhibited superior electrocatalytic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performances with an overpotential (η30) of 336 mV and 108 mV, respectively. NiV4 also displayed remarkable stability as confirmed by chronopotentiometry (24 h) and CV (after 5000 cycles). The excellent OER performance is possible due to the interatomic interaction and the heterojunction formation between V2O5 nanosheets and Ni MOF, resulting in the preferential adsorption of ⁎OOH reaction intermediates to Ni active sites. During HER, the interfacial interaction between V2O5 nanosheets and Ni MOF allowed the OH− to adsorb on the V5+ center. Furthermore, the Ni active sites simultaneously accelerated the Volmer step by promoting the H adsorption. The uniform mass transfer routes aid in fast charge transfer, resulting in excellent OER and HER performances. Interestingly, in the 2-electrode system, the NiV4 exhibited an overpotential of 1.81 V at 10 mA cm−2 and excellent durability over 15 h. For supercapacitor applications, the NiV4 exhibits efficient specific capacitance (546 Fg−1 at 1Ag−1). Furthermore, the NiV4 electrode provides significant long-term stability during the supercapacitor application, with the stability being consistent after 10,000 cycles. The NiV4 offers excellent water splitting and supercapacitor performance due to its multifunctional properties and remarkable structural integrity.