Guidong Yang

The electrocatalytic co-reduction of nitrate (NO3−) and carbon dioxide (CO2) into urea represents a potential avenue for achieving efficient urea production. However, this process involves intricate C–N coupling reactions and faces a severe kinetic mismatch between the reduction pathways. This disparity typically leads to a disproportionate coverage of key C- and N-containing intermediates on the catalyst surface, resulting in dominant competitive side reactions. Herein, we report the design of a heterogeneous FeNi@AC catalyst that integrates isolated Fe single atoms and Fe–Ni dual-atom sites at the atomic scale, enabling the efficient conversion of NO3− and CO2 into urea. Combined experimental and theoretical investigations reveal that the isolated Fe single-atom sites retain high nitrate reduction capability. Crucially, the introduction of Ni induces an electronic reconfiguration of the Fe center, which significantly lowers the energy barrier for CO2 activation (from 0.7 eV to 0.1 eV). This activation effectively bridges the kinetic gap between C- and N-species. Consequently, the FeNi@AC catalyst achieves a urea yield rate of 13.6 mmol g–1 h–1 and a Faradaic efficiency of 51.7% at –0.8 V (vs RHE). This work not only presents an active catalyst for urea synthesis but also provides a site-specific regulation strategy for designing multifunctional atomic-site catalysts tailored for complex tandem reactions.

Electrocatalytic CO2/NO3– coreduction to urea through C–N coupling (EcnRR) offers a low-carbon route that couples carbon utilization with nitrate valorization. However, its efficiency is limited by poor spatiotemporal synchronization of C- and N-derived intermediates, site competition and local repulsion at single active sites, and insufficient control over the NO3– reduction reaction (NtrRR) hydrogenation. Here, we construct a series of secondary-coordination-tunable single-atom Cu–alkynyl–X sites in conjugated microporous polymers (Cu–X–CMPs, X = N, C, S), where X → Cu σ coordination and an alkynyl π channel work together through triadic σ–π coupling to electronically program low-valent Cu atomic sites (Cuδ+). Experiments and theory show that N-coordinated Cu stabilizes the Cuδ+ working state, enhances local interfacial polarization, and reorganizes the interfacial hydrogen-bond network. These effects improve proton-coupled electron transfer (PCET) compatibility and increase the synchronized local coverages of *CO and *NHx near the active site. More importantly, Cu–N–CMPs establishes a sequential dual-N-species C–N coupling pathway initiated by *NH and completed by *NH2, with *CONH identified as the key intermediate in the first coupling step. As a result, Cu–N–CMPs delivers a Cu-site-normalized TOF of 1321.2 h–1 at −0.6 VRHE. In the membrane electrode assembly (MEA) electrolyzer, it further delivers a urea formation rate of 92.8 mmol gcat.–1 h–1 with 77.6% FEurea and stable operation for 85 h. This work demonstrates that Cu site electronic programming can coordinate sequential dual-N species C–N coupling, providing a transferable atomic-site engineering strategy for complex multi-intermediate electrocatalysis.

Electrocatalytic nitrate reduction (eNO3−RR) is widely recognized as a sustainable strategy for green ammonia production. However, the complex adsorption–activation–hydrogenation behavior of multiple nitrogen-oxygen intermediates and the intrinsic mismatch in proton-coupled electron transfer kinetics severely hinder the NH3 yield. Herein, a structurally engineered FeCo-MOF electrocatalyst featuring an asymmetric Co–O–Fe center was constructed via competitive coordination. The unique electronic orbital distribution in the Co–O–Fe bimetallic center promotes O-mediated charge transfer from Co to Fe. This charge redistribution induces enhanced electronic localization and asymmetry within the Co–O–Fe unit, thereby facilitating the activation and reduction of nitrogen-oxygen intermediates. Notably, in this asymmetric electronic configuration, the Co site enables efficient electron provisioning and promotes water dissociation to generate active hydrogen (Hads) species, ensuring well-matched proton-coupled electron transfer kinetics and accelerating the rapid conversion of the key *NO intermediate on electron-enriched Fe sites. Theoretical calculations further demonstrate that the asymmetric Co–O–Fe motif significantly lowers the thermodynamic barrier of *NO → *NOH step. The catalyst delivers a NH3 production rate of 0.653 mmol·cm−2·h−1 (1306 mmol·gcat−1·h−1) with a near-unity Faradaic efficiency (FE) of 99.8%. This study provides comprehensive insights into optimizing proton-coupled electron transfer dynamics and elucidating structure-performance relationships for advanced green-ammonia electrocatalysis.

Solar-driven CO2 methanation represents a promising strategy for reducing carbon footprints; however, the development of high-performance photothermal catalysts and their optimization strategies remains challenging. Here, we report a nickel (Ni) nanocluster-engineered CeO2 photocatalyst (denoted as NiNC/CeO2) to induce an enhanced Ni 3d orbital filling state and an interfacial electron-rich structure. These electronic modifications selectively accelerate H2 dissociation and C–H bonding steps for the HCOO* hydrogenation path, thereby achieving improved methane (CH4) formation rate (919.2 mmol·gcat−1·h−1) and selectivity (over 97%) with respect to the control samples free of the Ni nanocluster engineering. Detailed structural characterization and orbital-projected density of states analyses revealed that the enhanced performance can be attributed to the enriched 3d orbital filling at the Ni sites and 2p orbital filling at the Ni–O–Ce interface. These electronic configurations facilitate H2 dissociation and directed hydrogenation of CO2, thereby promoting efficient CO2 methanation. Additionally, the dual-path carrier migration and superior light absorption properties induced by the Ni-nanocluster structure are critical factors contributing to the high performance under photothermal catalytic (PTC) conditions.

Photoelectrochemical nitrate reduction to ammonia (PEC NO3RR) is a promising route for solar-driven ammonia synthesis. Yet, high ammonia yields in PEC NO3RR are largely confined to highly negative bias, which limits the overall energy utilization efficiency, whereas efficient operation under positive bias remains elusive. Herein, we constructed a CuNi-O/Si photoelectrocatalyst by introducing atomically dispersed interstitial oxygen atoms into the CuNi alloy lattice on silicon nanoarrays. The atomic interstitial oxygen induces local charge polarization, directing electron migration toward coordinated Cuδ+ and Niδ+ sites, thereby enhancing interfacial charge transfer. Crucially, the interstitial oxygen tunes a configuration inversion of the *NO intermediate from a strongly bound N-top configuration to a moderately adsorbed O-bridge configuration, mitigating overbinding and accelerating subsequent hydrogenation. Consequently, the CuNi-O/Si photoelectrocatalyst with an onset potential (+0.6 V vs RHE) exhibits a photocurrent density of −13.8 mA cm−2 and an ammonia yield rate of 27 μmol cm−2 h−1 at +0.3 V vs RHE under AM 1.5 illumination, corresponding to an incident photon-to-current efficiency of 58.5%. Additionally, this photoelectrocatalyst achieves continuous ammonia synthesis for 50 h using air and water under ambient conditions combined with nonthermal plasma. This work provides an atomic-level strategy of nonmetal interstitial tuning to develop functional materials for solar energy conversion.