TY - JOUR
T1 - Covalent ligation of Co molecular catalyst to carbon cloth for efficient electroreduction of CO2 in water
AU - Marianov, Aleksei N.
AU - Jiang, Yijiao
PY - 2019/5/5
Y1 - 2019/5/5
N2 - Electrochemical reduction of CO2 to CO in water catalysed by porphyrins is a viable way to environmentally friendly CO2 valorisation, while efficient catalyst immobilization on the electrode surface is one of the key challenges to answer. Herein we present a concept of "molecular wire" i.e. connection of the catalyst to electrode via a conductive covalent linker. To covalently immobilize Co porphyrin core onto carbon cloth we employed reduction of corresponding diazonium salt. "Wiring' via resulting phenylene group had profound effect on electrocatalytic performance. Formation of CO in neutral aqueous electrolyte at –1.05 V vs NHE (η = 500 mV) occurs with TOF of 8.3 s−1 while noncovalent counterpart has TOF of 4.5 s−1 only. Compared to the noncovalent mode, covalent ligation leads to 2.4 times higher surface density of electrochemically active species and maximum FE (CO) is achieved at 50 mV less negative potential. The catalyst accumulated 3.9‧105 TON in 24 h long electrolysis surpassing performance of drop-cast analogue by a factor of 3 and showed FE (CO) of up to 81%. Notably, the TON and TOF values achieved in our study are one of the highest reported to date surpassing those measured for Fe hydroxyporphyrins and Co porphyrin-based covalent organic frameworks. Electrokinetic analysis demonstrated that the electron transfer from electrode onto porphyrin moiety plays an important role in overall reaction kinetics and conductive link with the support is a key element of heterogeneous catalyst design.
AB - Electrochemical reduction of CO2 to CO in water catalysed by porphyrins is a viable way to environmentally friendly CO2 valorisation, while efficient catalyst immobilization on the electrode surface is one of the key challenges to answer. Herein we present a concept of "molecular wire" i.e. connection of the catalyst to electrode via a conductive covalent linker. To covalently immobilize Co porphyrin core onto carbon cloth we employed reduction of corresponding diazonium salt. "Wiring' via resulting phenylene group had profound effect on electrocatalytic performance. Formation of CO in neutral aqueous electrolyte at –1.05 V vs NHE (η = 500 mV) occurs with TOF of 8.3 s−1 while noncovalent counterpart has TOF of 4.5 s−1 only. Compared to the noncovalent mode, covalent ligation leads to 2.4 times higher surface density of electrochemically active species and maximum FE (CO) is achieved at 50 mV less negative potential. The catalyst accumulated 3.9‧105 TON in 24 h long electrolysis surpassing performance of drop-cast analogue by a factor of 3 and showed FE (CO) of up to 81%. Notably, the TON and TOF values achieved in our study are one of the highest reported to date surpassing those measured for Fe hydroxyporphyrins and Co porphyrin-based covalent organic frameworks. Electrokinetic analysis demonstrated that the electron transfer from electrode onto porphyrin moiety plays an important role in overall reaction kinetics and conductive link with the support is a key element of heterogeneous catalyst design.
KW - CO₂ electroreduction
KW - Electrochemistry
KW - Covalent immobilization
KW - Cobalt porphyrin
UR - http://www.scopus.com/inward/record.url?scp=85058408693&partnerID=8YFLogxK
UR - http://purl.org/au-research/grants/arc/DP14010243
UR - http://purl.org/au-research/grants/arc/DE120100329
U2 - 10.1016/j.apcatb.2018.11.084
DO - 10.1016/j.apcatb.2018.11.084
M3 - Article
AN - SCOPUS:85058408693
SN - 0926-3373
VL - 244
SP - 881
EP - 888
JO - Applied Catalysis B: Environmental
JF - Applied Catalysis B: Environmental
ER -