Oxygen evolution reaction on transition metal borides

The oxygen evolution reaction on the transition metal borides (mainly Co_xB and Ni_xB) was investigated with various composition ratio of BMetal and sintering temperature. The activity of oxygen evolution reaction became maximum at the composition range of BCo = 1 3 and BNi ≥ 1 3, respectively. The sintering temperature also affected largely the activity of oxygen evolution reaction and the metal borides with the composition ratio BMetal = 1 3 gave the highest activity at the sintering temperature lower than 300°C for nickel borides and 400 ∼ 500°C for cobalt borides. The oxygen evolution reaction on iron boride and lanthanum hexaboride was also briefly discussed, and the order of the activity of oxygen evolution reaction was as follows: {A figure is presented} The Tafel slope of oxygen evolution reaction on metal borides was varied from ca. 40 mV for Ni (ca 70 mV for Co) to ca. 120 mV with the increase in the activity of oxygen evolution reaction. The oxide formation became easier with the increase in the activity of oxygen evolution reaction and the differential capacity of the oxide formation in the range more cathodic than the oxygen evolution increased with the decrease in the apparent activation energy of oxygen evolution reaction at 0.60 V (HgHgO).