Simple generic self-assembly fabrication of transition metal borates on polyaminophenylboric acid modified foam nickel for highly-efficient overall water splitting

Abstract

Water electrocatalysis for hydrogen production as a prospect strategy to store renewable energy and reduce carbon emissions has attracted great attention, and exploring water electrolysis catalysts has become a research hotspot for widespread industrial water electrolysis application. Very recently, transition metal borates have been demonstrated great potential for electrocatalytic hydrogen or oxygen evolution in alkaline media. However, a generic method for fabricating transition metal borates as bifunctional oxygen catalysts are still challenging. Herein, through a two-step process including poly-aminophenylboronic acid electrodeposition and subsequent electrostatic self-assembly of transitional metal ions, for the first time, to our best knowledge, a simple and generic approach to fabricate polyaminophenylborate transition metal salt modified nickel foam electrodes (PAB-M/NF, M represents transition metal element) was developed for highly efficient water splitting. As a proof of concept, the obtained PAB-Ru/NF exhibited remarkable bifunctional HER and OER catalytic activities and stability in alkaline medium. To drive the HER and OER with a current density of 10 mA cm−2 in 1 M KOH electrolyte, PAB-Ru/NF only required an overpotential of 14 mV and 301 mV, respectively. Moreover, even at a great current density of 250 mA cm−2, PAB-Ru/NF can exhibit very favorable long-term stability for over 35 h. When assembled into an electrolyzer with PAB-Ru/NF as both the anode and cathode, a current density of 10 mA cm−2 can be achieved at a very low cell voltage of 1.50 V. In addition, the other PAB-M/NF catalysts (M including but not limited to Fe, Co and Ni) prepared by the same way also show excellent bifunctional HER and OER catalytic activities and durability. This study provides a prospective and economically feasible generic approach for developing practical bifunctional catalysts for industrial water electrolysis.