Co-W/CeO2 composite coatings for highly active electrocatalysis of hydrogen evolution reaction

Abstract Co-W/CeO 2 composite coatings were electrodeposited under galvanostatic conditions from a citrate plating bath containing suspended micro-CeO 2 particles. The composition, structure and morphology of the composite coatings were evaluated and compared when different concentrations of micro-CeO 2 particles are added. The as-prepared Co-W coating without CeO 2 has an amorphous structure. However, embedding CeO 2 into the Co-W matrix considerably improved the crystallinity of the Co-W alloy. The surface morphology study revealed that Co-W/CeO 2 composite coatings were more compact with fewer microcracks and defects than the Co-W coating. The electrocatalytic performance of these composite coatings for hydrogen evolution reaction (HER) was also investigated by liner sweep voltammetry and electrochemical impedance spectroscopy techniques in alkaline medium. Co-W/CeO 2 composite coatings gained remarkable improvement in HER activity which may be attributed to a synergistic eletrocatalytic effect between CeO 2 particles and Co-W matrix. The apparent exchange current density value (j 0 ) of the Co-W/CeO 2 composite coating was 15.6 times higher than that of the Co-W coating when the concentration of micro-CeO 2 particles in the plating bath is 7 gL -1 (denoted as M3), and the j 0 /R f ratio (intrinsic catalytic activity) was 3.72 × 10 −5 Acm −2 . Furthermore, M3 coating also showed good stability and its apparent activation energy (E a ) of HER was calculated to be 24.59 kJmol -1 , which was significantly lower than that of the Co-W coating.