Key Takeaways & Executive Findings
- •• Rational regulation of coordination environments on both photoanode and cathode enhances overall solar-driven CO2 conversion. • Defect-engineered FeNi catalysts on BiVO4 achieve a high OER photocurrent of 6.51 mA cm−2 at 1.23 VRHE. • Single-atom Co-N5 sites on N-rich carbon boost CO2-to-CO selectivity with faradaic efficiency >90%. • Integrated system reaches record CO production rate of 109.4 μmol cm−2 h−1 and solar conversion efficiency of 5.41%.
Abstract
Artificial carbon fixation is a promising pathway for achieving the carbon cycle and environment remediation. However, the sluggish kinetics of oxygen evolution reaction (OER) and poor selectivity of CO2 reduction seriously limited the overall conversion efficiencies of solar energy to chemical fuels. Herein, we demonstrated a facile and feasible strategy to rationally regulate the coordination environment and electronic structure of surface-active sites on both photoanode and cathode. More specifically, the defect engineering has been employed to reduce the coordination number of ultrathin FeNi catalysts decorated on BiVO4 photoanodes, resulting in one of the highest OER activities of 6.51 mA cm−2 (1.23 VRHE, AM 1.5G). Additionally, single-atom cobalt (II) phthalocyanine anchoring on the N-rich carbon substrates to increase Co–N coordination number remarkably promotes CO2 adsorption and activation for high selective CO production. Their integration achieved a record activity of 109.4 μmol cm−2 h−1 for CO production with a faradaic efficiency of >90%, and an outstanding solar conversion efficiency of 5.41% has been achieved by further integrating a photovoltaic utilizing the sunlight (>500 nm).
1. Introduction
The artificial carbon fixation is one of the greatest challenges for the field of modern chemistry concerning to sustainable energy sources and effective carbon dioxide (CO2) mitigation [1–5]. One promising approach involves the coupling of sunlight-driven photoanodes with dark cathodes for achieving oxygen evolution and CO2 reduction, presenting a feasible and promising solution to simulate the natural photosynthesis [6–10]. In this typical configuration, a highly active photoanode is essential for significantly reducing the energy barrier of oxygen evolution reaction (OER) to release protons and electrons, maximizing the efficiency of the overall solar energy conversion system [11–17].
Among diverse photoanode materials, bismuth vanadate (BiVO4) has attracted considerable attentions benefiting from its appropriate bandgap (2.4 eV), suitable valence edge positions, and low onset potential. To further promote OER activities, the rational construction of transition metal oxides or (oxy)hydroxides, especially for VIII metals (Fe, Co, Ni), on BiVO4 photoanode surfaces has attracted considerable attentions in recent years [18–21]. For example, Choi et al. [22] reported the electrodeposition of FeOOH/NiOOH dual catalysts on BiVO4 photoelectrodes, and a record-breaking photocurrent (4.5 mA cm−2 at 1.23 VRHE) has been achieved. Domen et al. [23] deposited NiFe bimetallic catalysts on BiVO4 photoanodes for improving the PEC activities up to 4.2 mA cm−2 at 1.23 VRHE. Our group previously demonstrated the synergy between iron and nickel of FeNi oxyhydroxides significantly improved the PEC water oxidation properties with 5.8 mA cm−2 at 1.23 VRHE for BiVO4 photoanodes [24]. Although diverse strategies have been extensively reported to decorate NiFe catalysts on BiVO4 photoelectrodes, the intrinsic roles of coordination environment and electronic structures of surface NiFe active sites on PEC water oxidation behaviors still remain ambiguous until now.
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Chaowei Wang, Laihong Geng, Yingpu Bi (2025). Highly Active Oxygen Evolution Integrating with Highly Selective CO2-to-CO Reduction. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01688-2
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Frequently Asked Questions
What is the main achievement of this study?
The study demonstrates a record CO production rate of 109.4 μmol cm−2 h−1 with faradaic efficiency >90% and a solar conversion efficiency of 5.41% by integrating a highly active BiVO4 photoanode with a single-atom Co-N5 cathode.
How was the oxygen evolution reaction improved?
By employing defect engineering to reduce the coordination number of ultrathin FeNi catalysts on BiVO4, achieving a photocurrent density of 6.51 mA cm−2 at 1.23 VRHE under AM 1.5G illumination.
What is the role of single-atom cobalt in CO2 reduction?
Single-atom cobalt (II) phthalocyanine anchored on N-rich carbon increases Co–N coordination, which enhances CO2 adsorption and activation, leading to high selectivity for CO production.
What is the significance of the coordination environment regulation?
Rational regulation of coordination environments on both photoanode and cathode is crucial for optimizing catalytic activity and selectivity, as demonstrated by the improved OER and CO2 reduction performance.
What are the potential applications of this technology?
This integrated photoelectrochemical system offers a sustainable route for solar-driven CO2 conversion to valuable chemicals, contributing to carbon neutrality and renewable energy storage.
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