Ni-W nanostructure well-marked by Ni selective etching for enhanced hydrogen evolution reaction

Abstract Designing active, stable and affordable electrocatalysts is a promising pathway for fulfilling the mankind's dream of preserving unsustainable fuel sources. Herein, the facile utilization of Romanesco-like and arrow-like nanostructures of Ni-W samples is introduced. Exclusive emphasis is placed on achievement of the unique nanostructure through cost-effective, repeatable and readily accessible two-step techniques, i.e. Ni-W electrodeposition approach followed by etching treatment. Microscopic study was fully utilized for surface morphology and structural investigation. The electrochemical analysis was used to evaluate the electrocatalytic activity and stability. The surface roughness of the Ni-W film electrodeposited by D.C = 90% and etched via acidic solution was up to 93.85, considerably higher than that of the Ni-W electrodeposited by D.C = 20% and without etched Ni-W films (55.36 and 41.51 respectively). Therefore, HER activity was improved with η 10 and η 20 of 169 and 226 mV vs. RHE, respectively, due to higher effective active surface for H + adsorption. The Tafel slope analysis suggests Volmer mechanism as the HER rate-determining step. The electrochemically active surface area was also enhanced from roughly 2 to 10 cm 2 . In addition, wettability was investigated by a contact angle of less than 65°, which indicates high penetration of electrolyte to the nanostructure. Rapid separation of bubbles on the arrow-like nanostructure of Ni-W films exhibited unstable H 2 bubbles on surface of the electrode.