Xin Wang

Multi‐metal catalysts offer opportunities for high activity and selectivity in CO ₂ electroreduction (eCO ₂ RR) through multiple active sites and synergistic effects; however, achieving high current densities remains challenging. Cu _x Ce _y Ag _z nanoparticles (NPs) were synthesized via a modified solvothermal method, with Cu ₉ Ce ₉ Ag ₁ identified as the optimal composition. This catalyst sustained activity up to −1 A cm ⁻² and delivered a partial current density of −707.2 mA cm ⁻² for C ₂₊ products at an iR‐corrected potential of −0.68 V. Ag promotes high local CO generation, while Ce modulates Cu oxidation states, optimizing Cu─O surface chemistry and *CO speciation to favor C─C coupling. In situ mass spectrometry indicated competitive proton utilization among H ₂ , ethylene, and methane, with *CO dimerization governing ethylene production. Operando Raman spectroscopy revealed enhanced *CO coverage, a higher *CO _atop /*CO _bridge ratio, stable Cu─O species, and increased local pH on Cu ₉ Ce ₉ Ag ₁ NPs, collectively suppressing the hydrogen evolution reaction and accelerating CO ₂ RR kinetics. These findings highlight the possibilities to rationally design multi‐metal catalysts to maximize synergetic effects, enabling high C ₂₊ selectivity at industrially relevant current densities.

The electrocatalytic synthesis of urea by coreduction of NO ₃ ⁻ and CO ₂ provides the basis to replace the energy‐intensive Bosch–Meiser process; however, such systems are inherently limited by competing reactions and urea selectivity. Scanning electrochemical cell microscopy (SECCM) with a cosputtered Co‐Cu alloy thin‐film materials library is used for the high‐throughput investigation of element composition‐dependent electrochemical activity for the coreduction of CO ₂ and NO ₃ ⁻ to urea. A NO ₃ ⁻ containing electrolyte is provided in the SECCM capillary while CO ₂ is offered through the gas phase. Comparison of linear sweep voltammograms in presence and absence of CO ₂ is the basis for finding Co‐Cu compositions which exhibit an increased overpotential for NO ₃ ⁻ reduction for matching the potentials for CO ₂ reduction, thus allowing the presence of the intermediates of both reactions in close vicinity at the catalytic sites. The most promising Co‐Cu element ratio for urea synthesis is synthesized as a powder catalyst and investigated in a model flow‐through electrolyzer concerning urea synthesis. These findings provide guidance for the rational design of Co‐Cu (Co _x Cu _100−x ) catalysts, the optimization and the identification of optimal working potentials as well as electrolyte compositions to facilitate CN coupling to urea with minimal loss caused by competing reactions.

Operando Raman spectroscopy captures the gradual transition from CO ₂ reduction to hydrogen evolution under increasingly cathodic potentials, revealing the pivotal role of interfacial water reorientation in initiating HER.

Wir schlagen eine hybride elektrokatalytisch‐bioelektrokatalytische Reaktionskaskade vor, die auf einer Gasdiffusionselektrode zur CO₂‐Reduktion unter selektiver Bildung von Methanol integriert ist. Ag‐Bi₂O₃ reduziert gasförmiges CO₂ bei neutralem pH‐Wert selektiv zu Formiat. Eine nachfolgende enzymatische Kaskade aus Formaldehyd‐Dehydrogenase und Alkohol‐Dehydrogenase, die beide von Nikotinamid‐Adenin‐Dinukleotid (NADH) abhängig sind, reduziert Formiat weiter sequentiell zu Formaldehyd und Methanol. Der enzymatisch oxidierte Redoxkofaktor NAD⁺ wird durch das Enzym Diaphorase regeneriert, das elektrochemisch an die Elektrode gekoppelt ist, indem es in ein Redoxpolymer auf Cobaltocen‐Basis eingebettet ist. Die Methanolbildung wird mithilfe eines hochselektiven Biosensors nachgewiesen, der auf Alkoholoxidase in Kombination mit Meerrettichperoxidase basiert, die in ein speziell angepasstes Redoxpolymer integriert sind. Die vorgeschlagene hybride elektrokatalytisch‐bioelektrokatalytische Kaskade ist ein Beispiel für eine allgemeine Strategie zur Verbesserung der Selektivität elektrokatalytischer Reaktionen und/oder zum Ersatz bioelektrochemisch anspruchsvoller Schritte wie der Synthese von Formiat aus CO₂ unter Verwendung sauerstoffempfindlicher Formiatdehydrogenasen durch robustere anorganische Elektrokatalysatoren.

We propose a hybrid electrocatalytic‐bioelectrocatalytic reaction cascade integrated on a gas diffusion electrode for CO₂ reduction under selective formation of methanol. Ag‐Bi₂O₃ selectively reduces gaseous CO₂ to formate at neutral pH conditions. A subsequent enzymatic cascade comprising formaldehyde dehydrogenase and alcohol dehydrogenase, which are both nicotinamide adenine dinucleotide (NAD)‐dependent, further reduce formate sequentially to formaldehyde and methanol. The enzymatically oxidized redox cofactor NAD⁺ is regenerated through the enzyme diaphorase which is electrochemically coupled to the electrode by embedding it into a cobaltocene‐based low‐potential redox polymer. Methanol formation is confirmed using a highly selective biosensor based on alcohol oxidase in combination with horseradish peroxidase integrated into a specifically adapted redox polymer. The proposed hybrid electrocatalytic‐bioelectrocatalytic cascade is an example for a general strategy for enhancing the selectivity of electrocatalytic reactions and/or to replace bioelectrochemically challenging steps such as the synthesis of formate from CO₂ using highly oxygen‐sensitive formate dehydrogenases by more robust inorganic electrocatalysts.

Transition metal and nitrogen co‐decorated carbon materials are promising platforms for CO ₂ electroreduction. A hard‐template 2‐step pyrolysis method is proposed for the fabrication of highly dispersed Ni and Cu atomic active sites on a 3D macroporous carbon matrix. The pyrrolic N‐type Ni−N _x sites serve as dominant active sites toward selective CO ₂ electroreduction to CO. The incorporation of Cu alters the distribution of N species and simultaneously optimizes the electronic state and geometric structure of the Ni−N _x moiety, thereby improving its adsorption and activation capacity for CO ₂ . Moreover, the isolated Cu atomic sites enhance the resistance of corresponding gas‐diffusion electrodes against electrolyte flooding. The optimal catalyst 3D NiCu‐69 achieves nearly exclusive production of CO with a Faraday efficiency (FE _CO ) of 98% at a current density of −700 mA cm ⁻² in a CO ₂ ‐gas‐fed flow‐through electrolyzer and delivers a CO production rate of 1363 mol(m ² s) ⁻¹ , which is exceeding most reported electrocatalysts. The FE _CO remained as high as 94% after electrolyzing at a current density of −100 mA cm ⁻² for 22 h. 3D NiCu‐69 exhibits a favorable performance in both acidic and neutral conditions, with a high FE _CO of ≈90.2% within the current density range of −100 to −500 mA cm ⁻² .

Tuning the activity, selectivity, and stability of electrocatalysts for the electrochemical CO₂ reduction reaction (eCO₂RR) is of high interest. Among the multitude of possible eCO₂RR products, formic acid/formate is not only of high industrial importance but even more importantly it can be obtained at nearly 100 % Faradaic efficiency if suitable catalysts are employed for the eCO₂RR. Recently, two distinct strategies to modulate the eCO₂RR over Bi‐based catalysts, namely phase modulation and functionalization with organic ligands, have come to the fore. This concept paper aims to string them together to accelerate their exploitation to design sophisticated electrocatalysts for the eCO₂RR.