Structural engineering of Cobalt Prussian blue analogues for enhanced electrochemical and electrocatalytic performance

Abstract

Cobalt-based Prussian Blue Analogues (Co-PBAs) were synthesized through a co-precipitation method followed by post synthesis treatment involving surface etching and thermal annealing to tailor the structure and electroactive properties. These modifications were comprehensively examined using various characterizations to assess their structural integrity and charge storage and catalytic capabilities. The spectroscopy results confirm the presence of cyanide (CN) group in PBAs, whereas after annealing, elimination of CN group, resulting PBA transformation into cobalt iron oxides (derived CoFeO). Raman analysis confirmed the signature peaks at 2100–2200 cm⁻¹ and 500–700 cm⁻¹ corresponding to the stretching vibrations of cyanide (CN) and Fe-C/Fe-N. X-ray photoelectron spectroscopy (XPS) corroborates the findings obtained from both Raman and Fourier transform infrared (FTIR) analyses. Electrochemical and electrocatalytic performances were evaluated in both two and three-electrode configurations. The etched Co-PBA showed highest specific capacitance (C_s) at low scan rate, superior energy and power density and low charge transfer resistance (R_ct) compared to pristine Co-PBA and derived CoFeO. In oxygen evolution reaction (OER), the etched PBA exhibited a low Tafel slope and overpotential values as compare to the other samples. As prototype demonstration, the device powered the hygrometer for 98 min, LEDs remained illuminated for 6 min 33 s, confirming its practical capability. These results highlighted that the etched Co-PBA exhibited improved electrochemical, electrocatalytic and prototype performance, demonstrating a strong correlation between structural evolution and electroactive performance.