BiPO 4 ‐Derived 2D Nanosheets for Efficient Electrocatalytic Reduction of CO 2 to Liquid Fuel

Coupling Curvature and Hydrophobicity: A Counterintuitive Strategy for Efficient Electroreduction of Nitrate into Ammonia

The electrochemical upcycling of nitrate (NO3-) to ammonia (NH3) holds promise for synergizing both wastewater treatment and NH3 synthesis. Efficient stripping of gaseous products (NH3, H2, and N2) from electrocatalysts is crucial for continuous and stable electrochemical reactions. This study evaluated a layered electrocatalyst structure using copper (Cu) dendrites to enable a high curvature and hydrophobicity and achieve a stratified liquid contact at the gas-liquid interface of the electrocatalyst layer. As such, gaseous product desorption or displacement from electrocatalysts was enhanced due to the separation of a wetted reaction zone and a nonwetted zone for gas transfer. Consequently, this electrocatalyst structure yielded a 2.9-fold boost in per-active-site activity compared with that with a low curvature and high hydrophilic counterpart. Moreover, a NH3 Faradaic efficiency of 90.9 ± 2.3% was achieved with nearly 100% NO3- conversion. This high-curvature hydrophobic Cu dendrite was further integrated with a gas-extraction membrane, which demonstrated a comparable NH3 yield from the real reverse osmosis retentate brine.

Enriching Metal-Oxygen Species and Phosphate Modulating of Active Sites for Robust Electrocatalytical CO2 Reduction

Direct electrochemical reduction of CO2 (CO2 RR) into value-added chemicals is a promising solution to reduce carbon emissions. The activity of CO2 RR is influenced deeply by the reaction microenvironment and electronic properties of the catalysts. Herein, the surface PO4 3- anions are tuned to modulate the local microenvironment and the electronic properties of the indium-based catalyst with abundant metal-oxygen species enabling efficient electrochemical conversion of CO2 to HCOO- . Indium nanoparticles coupled with PO4 3- anions (PO4 3- -In NPs) achieve a high selectivity of HCOO- up to 91.4% at a low potential of -0.98 V versus reversible hydrogen electrode (versus RHE) and a high HCOO- partial current density of 279.3 mA cm-2 at -1.1 V versus RHE in the electrochemical flow cell. In situ and ex situ characterizations confirm the PO4 3- anions keep stable on the surface of indium during CO2 RR, accelerating the generation of OCHO* intermediate. From density functional theory calculations, PO4 3- anions enrich the metal-oxygen species on the substrate to optimize the electronic structure of the catalysts and induce a local microenvironment with massive K+ ions on the interface, thus reducing the activation energy barrier of CO2 RR.

Electron-Rich Bi Nanosheets Promote CO2 ⋅- Formation for High-Performance and pH-Universal Electrocatalytic CO2 Reduction

Electrochemical CO₂ reduction reaction (CO₂ RR) to chemical fuels such as formate offers a promising pathway to carbon-neutral future, but its practical application is largely inhibited by the lack of effective activation of CO₂ molecules and pH-universal feasibility. Here, we report an electronic structure manipulation strategy to electron-rich Bi nanosheets, where electrons transfer from Cu donor to Bi acceptor in bimetallic Cu-Bi, enabling CO₂ RR towards formate with concurrent high activity, selectivity and stability in pH-universal (acidic, neutral and alkaline) electrolytes. Combined in situ Raman spectra and computational calculations unravel that electron-rich Bi promotes CO₂ ⋅^- formation to activate CO₂ molecules, and enhance the adsorption strength of *OCHO intermediate with an up-shifted p-band center, thus leading to its superior activity and selectivity of formate. Further integration of the robust electron-rich Bi nanosheets into III-V-based photovoltaic solar cell results in an unassisted artificial leaf with a high solar-to-formate (STF) efficiency of 13.7 %.

A Nanocomposite of Bismuth Clusters and Bi2 O2 CO3 Sheets for Highly Efficient Electrocatalytic Reduction of CO2 to Formate

The renewable-electricity-driven CO₂ reduction to formic acid would contribute to establishing a carbon-neutral society. The current catalyst suffers from limited activity and stability under high selectivity and the ambiguous nature of active sites. Herein, we report a powerful Bi₂ S₃ -derived catalyst that demonstrates a current density of 2.0 A cm^-2 with a formate Faradaic efficiency of 93 % at -0.95 V versus the reversible hydrogen electrode. The energy conversion efficiency and single-pass yield of formate reach 80 % and 67 %, respectively, and the durability reaches 100 h at an industrial-relevant current density. Pure formic acid with a concentration of 3.5 mol L^-1 has been produced continuously. Our operando spectroscopic and theoretical studies reveal the dynamic evolution of the catalyst into a nanocomposite composed of Bi⁰ clusters and Bi₂ O₂ CO₃ nanosheets and the pivotal role of Bi⁰ -Bi₂ O₂ CO₃ interface in CO₂ activation and conversion.