Electrodeposited Cobalt Nanoflake Arrays as an Efficient Anodic Catalyst for Direct Borohydride Fuel Cells

Direct borohydride fuel cells require highly efficient and cost-effective electrocatalysts for the borohydride oxidation reaction (BOR) on the anode. This study presents a simple electrodeposition method for directly producing metallic Co nanoflake arrays (Co NAs) on different conductive substrates. The Co NAs synthesized exhibit an open structure and a strong adhesion to the substrates, providing more abundant active sites and thereby being able to facilitate the mass and charge transfer kinetics of BOR. The Co NAs demonstrate excellent catalytic performance for the BOR without the use of noble metals. An impressive current density of up to 726 mA cm –2 at 0.65 V (vs reversible hydrogen electrode) was achieved, which is 5.3 and 2.5 times higher than that of regular Co nanoparticles and commercial Pt/C materials, respectively. In addition, the as-synthesized Co NAs were further successfully employed as the anodic catalyst in a fully liquid-fed NaBH 4 /H 2 O 2 fuel cell, resulting in a remarkable peak power density of 262.7 mW cm –2 at approximately 0.95 V and an open-circuit cell voltage of 1.83 V. This performance distinctly surpassed that of cells equipped with the control Pt/C electrode and is comparable to recent top-tier results in the field.