Electrolytic conversion of CO2 to proportionally tunable syngas using nickel-nitrogen doped carbon materials derived from Chlorella sp.

Chlorella sp., a common type of algae found in global surface waters, is prone to causing "blooms" and can accumulate significant amounts of nutrients such as nitrogen, phosphorus, and carbon. While carbon materials derived from Chlorella sp. are widely used in the field of adsorption, there are relatively few reports focused on electrocatalysis. This study utilized Chlorella sp. as a raw material to synthesize functional carbon materials, and prepared nitrogen-doped (CN), nickel-doped (CNi), and nitrogen-nickel co-doped (CNNi) carbon-based catalysts with both metal and non-metal elements. The results showed that the CN, CNi and CNNi catalysts possessed certain electrocatalytic properties, among which the CNNi material had the best electrocatalytic activity towards CO₂ reduction (CO₂RR). In 1.0 M KHCO_3, the CNNi catalyst exhibited an instantaneous current density of 15.4 mA/cm² under the potential of -0.82 V (vs. RHE). In terms of product selectivity, the Faraday efficiency of CO on the CNNi electrode was up to 90 % when the electrode potential was -0.62 V (vs. RHE), while the selectivity of the CN and CNi catalysts for CO was only 59 % under the optimal conditions. The co-doping of nitrogen and nickel significantly enhanced the electrocatalytic activity and the selectivity towards CO of Chlorella-based carbon materials.