Polystyrene spheres-templated mesoporous carbonous frameworks implanted with cobalt nanoparticles for highly efficient electrochemical nitrate reduction to ammonia

• Electrocatalytic nitrate reduction reaction (eNO3RR) to ammonia (NH3) provides an intriguing approach for both environmental denitrification and sustainable NH3 synthesis. Herein, we report the fabrication of hierarchically mesoporous Co nanoparticles decorated N-doped carbon composites as a highly efficient electrocatalyst for eNO3RR by using monodispersed polystyrene spheres (PS) as sacrificial templates (MR Co-NC). By taking advantage of the large specific area of the pore-rich structures and the high intrinsic activity of metallic Co, the MR Co-NC shows remarkable activity toward eNO3RR, which achieves a partial current density of 268 mA cm-2 with a Faradaic efficiency (FE) of 95.35 +/- 1.75 % and a generation rate of 1.25 +/- 0.023 mmol h-1 cm-2 for NH3 production under the optimal conditions. The porous carbon skeleton was found to play a dual role by simul-taneously protecting the active sites from oxidation and facilitating long-range charge and mass transfer. Theoretical calculations reveal a lower energy barrier of the rate-determining step (*NO2 + H2O + 2e- -> *NO + 2OH-) on the metallic Co of MR Co-NC over beta-Co(OH)2 formed by the reconstruction of carbon-free Co nanoparticles.

Ämnesord

NATURVETENSKAP  -- Kemi -- Materialkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Materials Chemistry (hsv//eng)

Nyckelord

Nitrate reduction reaction

Hierarchically porous carbon skeleton

Co nanoparticles

Heterogeneous electrocatalysis

in-situ Raman

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