Self-CO₂ Recycling Photocatalytic Fuel Cell for Enhancing Degradation of Pollutants and Production of Carbon-Neutral Fuel

Abstract

Photoelectrochemical oxidation is considered a promising way for the treatment of refractory organic wastewater owing to its high efficiency and low cost. However, CO2 was still the final emission product in this system. Here, we designed a novel CO2 self-driving and self-recycling photocatalytic fuel cell (PFC) system for enhancing the degradation of refractory organic pollutants and ultimately converting it into fuel. The carbon-neutral PFC system achieved an increase of 40% in organics removal and an extra C1 fuel yield rate of 6.7 μmol g–1 h–1, compared to the conventional photocatalytic system. CO2 produced from wastewater degradation in the anode can be spontaneously supplied to the rotating cathode under positive pressure. The CO2 reduction reaction occurring at the cathode accelerated the electron–hole separation in photoanode and facilitated the formation of C1 fuel in the cathode. The isotope tracer experiment confirmed that the carbon source of C1 fuel products was from organics. Therefore, the light-dependent self-CO2 recycling PFC system provides new insight into the spontaneous conversion from refractory organic pollutants to green fuel.

An Overview of Solar-Driven Photoelectrochemical CO2 Conversion to Chemical Fuels

“…Similar to p -type semiconductors, n -type semiconductors as photoanodes can also harvest incident light with appropriate energy to generate electron–hole pairs. Photoelectrons arriving at the cathode via the external circuit lower the external bias required for CO 2 reduction, while holes migrate to the photoanode surface to oxidize water or some pollutants . Compared with photocathodes, photoanodes made of Earth-abundant n -type semiconductors are low-toxic or nontoxic and highly stable in aqueous media.…”

“…Photoelectrons arriving at the cathode via the external circuit lower the external bias required for CO 2 reduction, while holes migrate to the photoanode surface to oxidize water or some pollutants. 88 Compared with photocathodes, photoanodes made of Earth-abundant n-type semiconductors are low-toxic or nontoxic and highly stable in aqueous media. The performance of photoanode-driven PEC cell is determined by the photoanode and the electrocathode, and the electrocathode can be tuned to achieve higher overall efficiency of PEC cell and adjust reduction products.…”

Synergy of photocatalysis and fuel cells: A chronological review on efficient designs, potential materials and emerging applications

“…The CO 2 generated at anode upon wastewater degradation was continuously supplied to rotating cathode ( Figure 10 ). The CO 2 reduction reaction occurring at the cathode accelerated the electron−hole separation in photoanode and facilitated the formation of C1 fuel in the cathode ( Zhang et al, 2020b ). A recent report which investigated the role of CO 2 in the photocatalytic fuel cell drew many interesting scientific conclusions.…”

“…Gas channel. (B) Current response and Faraday efficiency of CO 2 reduction (C) by-product analysis in different operating system within 5 h. Reproduced with permission ( Zhang et al, 2020b ), Copyright 2020, American Chemical Society.…”