Researchers achieve efficient electro-oxidation of glycerol to formate under room temperature

Glycerol is a key byproduct of biodiesel fabrication, and its production has increased proportionally with the growth of biodiesel production. Glycerol electrooxidation is considered as an innovative strategy due to its low theoretical potential and the elimination of the need for external toxic oxidative agents, pressurized oxygen, and high temperature. 

Ni-based catalysts featured with abundant supply, low cost, and corrosion resistance have been used for glycerol electrooxidation reactions. However, the onset potential was subjected to the high generation potential of NiOOH, which is 1.35 V vs. RHE, leading to inferior electrooxidation activity.

In a study published in Angewandte Chemie-International Edition, a research team led by Prof. WU Zhongshuai and Prof. XIAO Jianping from the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences developed a highly active Cu-doped NiCo alloy (Cu-NiCo/NF) catalyst, and constructed an energy-saving nitrate reduction system coupled with glycerol oxidation, achieving high glycerol electrooxidation activity and selectivity to produce formate at room temperature.

The researchers fabricated this novel high-performance alloy catalyst, Cu-NiCo/NF, through one-step electrodeposition. The catalyst exhibited exceptional glycerol oxidation reaction (GOR) performance, requiring only 1.23 and 1.33 V vs. RHE to achieve 10 and 100 mA cm^-2, respectively, while achieving a Faraday efficiency for formate of 93.8%.

Then, the researchers confirmed the structural stability of the Cu-NiCo/NF catalyst. They found that the rapid generation of NiIII-OOH and CoIII-OOH as active species were promptly consumed during GOR, and that Cu doping in NiCo reduced the energy barrier and △G of the C-O coupling process, resulting in superior performance of electrocatalytic GOR.

Moreover, the researchers demonstrated that the Cu-NiCo/NF catalyst performed high activity and selectivity for the nitrate reduction reaction (NO₃-RR). 

Using Cu-NiCo/NF as a bifunctional catalyst, the researchers established a NO₃-RR||GOR system to produce NH₃ and formate simultaneously, requiring only 1.11 and 1.37 V to achieve 10 and 100 mA cm^-2, respectively. The system exhibited excellent long-term stability for up to 144 hours, with formic acid remaining the primary product at the anode. When the glycerol conversion rate reached 87.6%, the formation yield was 80.6%.

"This work not only develops a bifunctional electrocatalyst for GOR and nitrate reduction with high catalytic activity but also provides a new strategy for electrochemical refinery with product upgrades," said Prof. WU.