Adjustable anchoring of Ni/Co cations by oxygen-containing functional groups on functionalized graphite paper and accelerated mass/electron transfer for overall water splitting

Abstract

Highly efficient bifunctional electrocatalysts capable of simultaneous hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are very important for overall water splitting to produce hydrogen. Herein, we report a NiCo sulfide–NiCo oxide heterointerface (NCS–NCO) with a unique cellular network of porous nanosheets supported on functionalized graphite paper (FGP) with oxygen-containing functional groups. We use a simple electrochemical method to prepare the FGP support electrode, and regulate the content of oxygen-containing functional groups on the surface of FGP to determine the optimum morphology, and thereby improve the OER/HER dynamics for NCS–NCO/FGP. This innovative electrode exhibits extremely high electrocatalytic activity with an ultra-low potential of only 1.481 V at a current density of 10 mA cm⁻² for overall water splitting, even better than a RuO₂/FGP‖Pt/C/FGP electrode (1.583 V). The results demonstrate that metal cations (Ni and Co) can be quickly anchored, regulated, and grown on FGP. The optimum chemical composition allows the catalyst to have a unique cellular network with large numbers of active sites for fast mass transfer. Moreover, the close-contact heterointerface of NCS–NCO promotes the electron transfer among NCS, NCO, and FGP. This work provides a new method for constructing efficient and low-cost electrocatalysts for overall water splitting for industrial applications.