Enhancing the Cooperative Catalytic Effect in Ni/Co Hydr(oxy)oxide Porous Electrodes for Overall Water Splitting and Glucose Sensing

Application of non-noble metal electrocatalysts in energy conversion and electrochemical sensing is of utmost importance. Herein, the enhancement in the electrocatalytic water splitting and nonenzymatic glucose sensing in alkaline media was realized from the synergistic effect of porous Ni/Co hydr(oxy)oxide structures grown on nickel foam via a facile bubble-templated electrodeposition approach followed by catalytic activation. The effect is likely due to synergy between the low overpotential of nickel and higher adsorption of hydrogen for cobalt in combination with enhanced surface area, where better diffusion of electrolyte in the interconnected pores and low charge-transfer resistance is best realized with the Ni/Co = 1:1 electrode. The overpotential for catalytic current density of 20 mA cm^-2 is 132 mV for hydrogen evolution reaction (HER) and 338 mV for oxygen evolution reaction (OER) with the corresponding Tafel slopes of 55.3 and 66.1 mV dec^-1, respectively. In a two-electrode configuration, the same Ni/Co = 1:1 electrodes allow the current density of 10 mA cm^-2 to be achieved at a stable cell potential of 1.71 V. Moreover, the same electrode shows an excellent glucose sensitivity of 6.6 mA mM^-1 cm^-2 with minimal interference from uric and ascorbic acids.