Polypyrrole regulates Active Sites in Co‐based Catalyst in Direct Borohydride Fuel Cells

Abstract

Direct borohydride fuel cells (DBFCs) convert borohydride (NaBH4) chemical energy into clean electricity. However, catalytic active site deactivation in NaBH4 solution limits their performance and stability. We propose a strategy to regulate active sites in Co‐based catalysts using polypyrrole modification (Co‐PX catalyst) to enhance electrochemical borohydride oxidation reaction (eBOR). As an anode catalyst, the synthesized Co‐PX catalyst exhibits excellent eBOR performance in DBFCs, with current density of 280 mA·cm‐2 and power density of 151 mW·cm‐2, nearly twice that of the unmodified catalyst. The Co‐PX catalyst shows no degradation after 120‐hour operation, unlike the rapidly degrading control. In‐situ electrochemical attenuated total reflection Fourier‐transform infrared spectroscopy (ATR‐FTIRS) and density functional theory (DFT) suggest that polypyrrole‐modified carbon support regulate the charge distribution, increasing oxidation state and optimizing adsorption/desorption of intermediates. A possible reaction pathway is proposed. This work presents a promising strategy for efficient polymer‐modulated catalysts in advanced DBFCs.

Engineering Partially Oxidized Gold via Oleylamine Modifier as a High-Performance Anode Catalyst in a Direct Borohydride Fuel Cell

“…The adsorption band at ∼2268 cm –1 appears with the increase in the applied oxidizing potential, which can be assigned to absorbed BH 4 – species. , For AuC-OLA, the signal of *BH 4 – species in the FTIR spectra at 0.17 V vs RHE is more obvious than that of commercial AuC, indicating a stronger adsorption on partially oxidized Au (Figure e,f), consistent with the results of DFT calculations. Additionally, the band at ∼1415 cm –1 observed at ∼0.37 V vs RHE belongs to the asymmetric B–O stretching mode in the near-linear molecule B–O–B, − which is likely to sign the possible polymerization of BO 2 – on the surface of the electrode. , Also, a negative peak at 1170 cm –1 is found, corresponding to the *BH 3 species, considered an intermediate of the oxidized *BH 4 – during BOR (Figure g,h). ,, The peak of the *BH 3 species for AuC-OLA emerges at 0.17 V vs RHE, while the peak for commercial AuC appears only after 0.27 V vs RHE. This phenomenon indicates that the oxidation of BH 4 – on AuC-OLA is easier than on commercial AuC, confirming that partially oxidized Au can promote the process of BOR.…”

“…According to the reported literature, the direct oxidation of BH 4 – begins with the formation of adsorbed BH 3 (*BH 3 , * represents the absorbed state) on the catalyst surface. , Therefore, to gain deeper insights into the influence of electronic structures for Au on BOR, differential charge density analysis was employed for intermediate *BH 3 + *H on the surfaces of different valence states. As depicted in Figure d−f, significant electron transfer occurs between the surfaces of different valence states and the BH 3 group.…”