Neodymium-Doped Novel Barium Tungstate Nanospindles for the Enhanced Oxygen Evolution Reaction

Abstract

In this work, pristine, 0.02, 0.04, and 0.06 M neodymium (Nd)-doped barium tungstate nanostructures were synthesized via a simple co-precipitation method for the water oxidation process. The obtained X-ray diffraction high-intensity peak at a 2θ value of 26.4°corresponding to the (112) lattice plane confirmed the formation of a tetragonal structure of BaWO 4 . Moreover, the BaWO 4 morphology was examined by scanning electron microscopy, which showed the existence of nanospindles. An energydispersive X-ray spectrum confirmed the subsistence of the produced materials, for example, barium (Ba), tungsten (W), oxide (O), and neodymium (Nd), with weight percentages of 28.58, 46.63, 16.64, and 8.16%, respectively. The 0.04 M Nd-doped BaWO 4 product was explored to attain a high surface area of 18.18 m 2 /g, a pore volume of 0.079 cm 3 /g, and a pore diameter of 2.215 nm. Compared to the other prepared electrodes, the 0.04 M Nd-doped BaWO 4 product exhibited low overpotential values of 330 mV and 450 mV to deliver current densities of 10 mA/cm 2 and 50 mA/ cm 2 , respectively. In addition, the optimized electrode achieved a small Tafel slope value of 158 mV dec −1 and followed the Volmer− Heyrovsky mechanism. Moreover, the electrical conductivity of BaWO 4 was tuned due to the addition of a rare-earth metal dopant, and it exhibited the charge-transfer resistance and solution resistance values of 0.98 and 1.01 Ω, respectively. The prepared electrocatalyst was further studied by using cyclic voltammetry, and it exhibited a high double-layer capacitance value of 29.3 mF/ cm 2 and high electrochemically active surface areas of 1.465 cm 2 . The electrochemical performance was greatly improved depending on the concentration of the doping agent, and it was well consistent with the obtained results. The best electrocatalyst was subjected to a chronoamperometry test, which exhibited excellent stability even after 20 h. Hence, this work suggests that alkaline metal tungstates have a cost-effective, efficient, and promising electrocatalyst, and it is a new approach for the water oxidation process.