Boosting Electrochemical Reduction of CO2 to Formate over Oxygen Vacancy Stabilized Copper–Tin Dual Single Atoms Catalysts

Designing reasonable atomic structures is essential in modulating the selectivity of the valuable products produced in the electrochemical CO₂ reduction. Herein, a Cu Sn diatomic sites electrocatalyst stabilized by double oxygen vacancies on CeO_2-x is constructed, which exhibits superior electrochemical selectivity toward formate, achieving a 90.0% Faradaic efficiency at formate partial current density of 216.8 mA cm⁻² with the applied bias of −1.2 V versus REH. The experimental characterizations and theoretical calculations highlight the significance of the synergistic effect of Cu and Sn diatoms on reducing the activation energy and promoting the formation of intermediate ^*OCHO, which accounts for its high selectivity toward formate. Meanwhile, the oxygen vacancies on the CeO_2-x also play a pivotal role in manipulating the electrochemical performance and stability, which underlines the importance of regulating the electronic metal-support interaction between Cu Sn diatoms and CeO_2-x. This work demonstrates an effective method to design efficient electrochemical CO₂ reduction catalysts by modulating the surface structures of single-atoms anchored support.     

Boosting Industrial-Level CO2 Electroreduction of N-Doped Carbon Nanofibers with Confined Tin-Nitrogen Active Sites via Accelerating Proton Transport Kinetics

The development of highly efficient robust electrocatalysts with low overpotential and industrial-level current density is of great significance for CO₂ electroreduction (CO₂ER), however the low proton transport rate during the CO₂ER remains a challenge. Herein, a porous N-doped carbon nanofiber confined with tin-nitrogen sites (Sn/NCNFs) catalyst is developed, which is prepared through an integrated electrospinning and pyrolysis strategy. The optimized Sn/NCNFs catalyst exhibits an outstanding CO₂ER activity with the maximum CO FE of 96.5%, low onset potential of −0.3 V, and small Tafel slope of 68.8 mV dec⁻¹. In a flow cell, an industrial-level CO partial current density of 100.6 mA cm⁻² is achieved. In situ spectroscopic analysis unveil the isolated Sn N site acted as active center for accelerating water dissociation and subsequent proton transport process, thus promoting the formation of intermediate *COOH in the rate-determining step for CO₂ER. Theoretical calculations validate pyrrolic N atom adjacent to the Sn N active species assisted reducing the energy barrier for *COOH formation, thus boosting the CO₂ER kinetics. A Zn-CO₂ battery is designed with the cathode of Sn/NCNFs, which delivers a maximum power density of 1.38 mW cm⁻² and long-term stability.     

Molecular Modulation of Sequestered Copper Sites for Efficient Electroreduction of Carbon Dioxide to Methane

The sustainable production of methane (CH₄) via the electrochemical conversion of carbon dioxide (CO₂) is an appealing approach to simultaneously mitigating carbon emissions and achieving energy storage in chemical bonds. Copper (Cu) is a unique material to produce hydrocarbons and oxygenates. However, selective methane generation on Cu remains a great challenge due to the preferential *CO dimerization pathway toward multi-carbon (C₂₊) products at neighboring catalytic sites. Herein, a conjugated copper phthalocyanine polymer (CuPPc) is designed by a facile solid-state method for highly selective CO₂-to-CH₄ conversion. The spatially isolated Cu N₄ sites in CuPPc favor the *CO protonation to generate the key *CHO intermediate, thus significantly promoting the formation of CH₄. As a result, the CuPPc catalyst exhibits a high CH₄ Faradaic efficiency of 55% and a partial current density of 18 mA cm⁻² at −1.25 V versus the reversible hydrogen electrode. It also stably operates for 12 h. This study may offer a new solution to regulating the chemical environment of the active sites for the development of highly efficient copper-based catalysts for electrochemical CO₂ reduction.     

A New Strategy for Accelerating Dynamic Proton Transfer of Electrochemical CO2 Reduction at High Current Densities

Developing single-atom electrocatalysts with high activity and superior selectivity at a wide potential window for CO₂ reduction reaction (CO₂RR) still remains a great challenge. Herein, a porous Ni N C catalyst containing atomically dispersed Ni N₄ sites and nanostructured zirconium oxide (ZrO₂@Ni-NC) synthesized via a post-synthetic coordination coupling carbonization strategy is reported. The as-prepared ZrO₂@Ni-NC exhibits an initial potential of −0.3 V, maximum CO Faradaic efficiency (F.E.) of 98.6% ± 1.3, and a low Tafel slope of 71.7 mV dec⁻¹ in electrochemical CO₂RR. In particular, a wide potential window from −0.7 to −1.4 V with CO F.E. of above 90% on ZrO₂@Ni-NC far exceeds those of recently developed state-of-the-art CO₂RR electrocatalysts based on Ni N moieties anchored carbon. In a flow cell, ZrO₂@Ni-NC delivers a current density of 200 mA cm⁻² with a superior CO selectivity of 96.8% at −1.58 V in a practical scale. A series of designed experiments and structural analyses identify that the isolated Ni N₄ species act as real active sites to drive the CO₂RR reaction and that the nanostructured ZrO₂ largely accelerates the protonation process of *CO₂⁻ to *COOH intermediate, thus significantly reducing the energy barrier of this rate-determining step and boosting whole catalytic performance.     

Nanoscale Management of CO Transport in CO2 Electroreduction: Boosting Faradaic Efficiency to Multicarbon Products via Nanostructured Tandem Electrocatalysts

Tandem catalysis presents a promising strategy to improve the selectivity toward multicarbon products in the electrocatalytic carbon dioxide reduction reaction (CO₂RR). For CO₂RR, CO is a critical intermediate for producing multicarbon products. However, the management of CO localization and CO diffusion remains underexplored despite its critical role. Herein, a 3D tandem catalyst electrode with silver nanoparticles (Ag NPs) is designed to generate CO as an intermediate product within a copper (Cu) nanoneedle array. Via this nanostructured design, CO₂ forms C²⁺ products with a high Faradaic efficiency (FEC²⁺) of 64% in an H-cell and 70% in a flow cell with a current density of 350 mA cm⁻². These figures-of-merit are currently among the top literature reports. More importantly, in situ Raman spectroscopy and finite-element method calculations are employed to elucidate the origins of enhanced selectivity. These approaches reveal the crucial role of prolonging the CO diffusion path length for improving CO utilization during CO₂ conversion with tandem catalyst systems. The favorable CO2RR FEC²⁺ in two distinct environments (H-cell and flow cell) further corroborates that this effect is not limited to a particular reactor environment. Overall, this study provides new insights for designing tandem catalysts for improved CO₂RR selectivity to C²⁺ products.     

In Situ Structure Refactoring of Bismuth Nanoflowers for Highly Selective Electrochemical Reduction of CO2 to Formate

The electrocatalytic CO₂ reduction reaction (CO₂RR) has been considered a promising route toward carbon neutrality and renewable energy conversion. At present, most bismuth (Bi) based electrocatalysts are adopted to reduce CO₂ to formate (HCOOH). However, the mechanism of different Bi nanostructures on the electrocatalytic performance requires more detailed exposition. Herein, a combined chemical replacement and electrochemical reduction process is reported to realize in situ morphology reconstruction from Bi@Bi₂O₃ nanodendrites (Bi@Bi₂O₃-NDs) to Bi nanoflowers (Bi-NFs). The Bi@Bi₂O₃-NDs are proven to undergo a two-step transformation process to form Bi-NFs, aided by Bi₂O₂CO₃ as the intermediate in KHCO₃ solution. Extensive surface reconstruction of Bi@Bi₂O₃-NDs renders the realization of tailored Bi-NFs electrocatalyst that maximize the number of exposed active sites and active component (Bi⁰), which is conducive to the adsorption and activation of CO₂ and accelerated electron transfer process. The as-prepared Bi-NFs exhibit a Faradaic efficiency (FE_formate) of 92.3% at −0.9 V versus RHE and a high partial current density of 28.5 mA cm⁻² at −1.05 V versus RHE for the electroreduction of CO₂ to HCOOH. Moreover, the reaction mechanism is comprehensively investigated by in situ Raman analysis, which confirms that *OCHO is a key intermediate for the formation of HCOOH.     

Pre-Activation of CO2 at Cobalt Phthalocyanine-Mg(OH)2 Interface for Enhanced Turnover Rate

Cobalt phthalocyanine (CoPc) anchored on heterogeneous scaffold has drawn great attention as promising electrocatalyst for carbon dioxide reduction reaction (CO₂RR), but the molecule/substrate interaction is still pending for clarification and optimization to maximize the reaction kinetics. Herein, a CO₂RR catalyst is fabricated by affixing CoPc onto the Mg(OH)₂ substrate primed with conductive carbon, demonstrating an ultra-low overpotential of 0.31 ± 0.03 V at 100 mA cm⁻² and high faradaic efficiency of >95% at a wide current density range for CO production, as well as a heavy-duty operation at 100 mA cm⁻² for more than 50 h in a membrane electrode assembly. Mechanistic investigations employing in situ Raman and attenuated total reflection surface-enhanced infrared absorption spectroscopy unravel that Mg(OH)₂ plays a pivotal role to enhance the CO₂RR kinetics by facilitating the first-step electron transfer to form anionic *CO₂⁻ intermediates. DFT calculations further elucidate that introducing Lewis acid sites help to polarize CO₂ molecules absorbed at the metal centers of CoPc and consequently lower the activation barrier. This work signifies the tailoring of catalyst-support interface at molecular level for enhancing the turnover rate of CO₂RR.     

Simultaneous CO2 and H2O Activation via Integrated Cu Single Atom and N Vacancy Dual-Site for Enhanced CO Photo-Production

Photocatalytic conversion of CO₂ into fuels using pure water as the proton source is of immense potential in simultaneously addressing the climate-change crisis and realizing a carbon-neutral economy. Single-atom photocatalysts with tunable local atomic configurations and unique electronic properties have exhibited outstanding catalytic performance in the past decade. However, given their single-site features they are usually only amenable to activations involving single molecules. For CO₂ photoreduction entailing complex activation and dissociation process, designing multiple active sites on a photocatalyst for both CO₂ reduction and H₂O dissociation simultaneously is still a daunting challenge. Herein, it is precisely construct Cu single-atom centers and two-coordinated N vacancies as dual active sites on CN (Cu₁/N_2CV-CN). Experimental and theoretical results show that Cu single-atom centers promote CO₂ chemisorption and activation via accumulating photogenerated electrons, and the N_2CV sites enhance the dissociation of H₂O, thereby facilitating the conversion from COO* to COOH*. Benefiting from the dual-functional sites, the Cu₁/N_2CV-CN exhibits a high selectivity (98.50%) and decent CO production rate of 11.12 µmol g⁻¹ h⁻¹. An ingenious atomic-level design provides a platform for precisely integrating the modified catalyst with the deterministic identification of the electronic property during CO₂ photoreduction process.     

Accelerating Proton and Electron Transfer Enables Highly Active Fe─N─C Catalyst for Electrochemical CO2 Reduction

Atomically dispersed Fe─N─C catalysts display great potential for efficient CO production in the field of electrochemical CO₂ reduction (ECR), but still suffer from unsatisfactory activity limited by the slow proton and electron transfer during the ECR process. Here, a superior Fe─N─C electrocatalyst is designed by anchoring the individual FeN₄ sites and Fe nanoparticles onto highly conductive carbon nanotubes. The resultant catalyst displays a commendable CO partial current density of 16.01 mA cm⁻² with a turnover frequency of 3519.6 h⁻¹ at −0.65 V in an H-type cell, and also exhibits CO selectivity > 90% under high current density over 120 mA cm⁻² in a flow cell. This remarkable activity exceeds a host of previously reported Fe─N─C catalysts. The findings indicate that the carbon nanotube facilitates CO production due to its strong capability of electron transport and charge transfer. In situ spectroscopic analysis, controlled experiments, and theoretical calculations reveal that Fe nanoparticles effectively promote water dissociation and the subsequent protonation step, accelerate the formation of ^*COOH intermediate, and thus greatly enhance the ECR activity.     

Hierarchical Cross-Linked Carbon Aerogels with Transition Metal-Nitrogen Sites for Highly Efficient Industrial-Level CO2 Electroreduction

Developing highly efficient carbon aerogels (CA) electrocatalysts based on transition metal-nitrogen sites is critical for the CO₂ electroreduction reaction (CO₂RR). However, simultaneously achieving a high current density and high Faradaic efficiency (FE) still remains a big challenge. Herein, a series of unique 3D hierarchical cross-linked nanostructured CA with metal-nitrogen sites (M N, M = Ni, Fe, Co, Mn, Cu) is developed for efficient CO₂RR. An optimal CA/N-Ni aerogel, featured with unique hierarchical porous structure and highly exposed M-N sites, exhibits an unusual CO₂RR activity with a CO FE of 98% at −0.8 V. Notably, an industrial current density of 300 mA cm⁻² with a high FE of 91% is achieved on CA/N-Ni aerogel in a flow-cell reactor, which outperforms almost all previously reported M-N/carbon based catalysts. The CO₂RR activity of different CA/N-M aerogels can be arranged as Ni, Fe, Co, Mn, and Cu from high to low. In situ spectroelectrochemistry analyses validate that the rate-determining step in the CO₂RR is the formation of *COOH intermediate. A Zn CO₂ battery is further assembled with CA/N-Ni as the cathode, which shows a maximum power density of 0.5 mW cm⁻² and a superior rechargeable stability.     

Hydroxypillar[5]arene-Confined Silver Nanocatalyst for Selective Electrochemical Reduction of CO2 to Ethanol

CO is usually the dominant product on silver-based catalysts in electrochemical CO₂ reduction reaction (CO₂RR) possibly due to weak *CO adsorption. In this report, a hydroxypillar[5]arene-extended porous polymer-confined silver catalyst (PAF-PA5-Ag-0.8) for electrochemical CO₂RR which can selectively produce ethanol with a maximum Faradaic efficiency of 55% at 11 mA cm⁻¹ is described. The study reveals that the hydroxypillar[5]arene-confined Ag clusters are the active sites for ethanol formation. Moreover, temperature-programmed desorption measurements demonstrate an enhanced adsorption strength of CO* on PAF-PA5-Ag-0.8 compared with that on commercial Ag nanoparticles, which is favored by the C-C coupling to form ethanol. The density functional theory study indicates that the confined Ag clusters in PAF-PA5-Ag-0.8 contribute to high C₂ selectivity in CO₂RR through facilitating *COOH formation, stabilizing *CO intermediates, and inhibiting hydrogen evolution. This work provides a new design strategy by modulating *CO adsorption strength on non-copper electrocatalysts in converting CO₂ into “green” C₂ products.     

Regulating the Metallic Cu–Ga Bond by S Vacancy for Improved Photocatalytic CO2 Reduction to C2H4

Artificial photosynthesis, which converts carbon dioxide into hydrocarbon fuels, is a promising strategy to overcome both global warming and energy crisis. Herein, the geometric position of Cu and Ga on ultra-thin CuGaS₂/Ga₂S₃ is oriented via a sulfur defect engineering, and the unprecedented C₂H₄ yield selectivity is ≈93.87% and yield is ≈335.67 µmol g⁻¹ h⁻¹. A highly delocalized electron distribution intensity induced by S vacancy indicates that Cu and Ga adjacent to S vacancy form Cu–Ga metallic bond, which accelerates the photocatalytic reduction of CO₂ to C₂H₄. The stability of the crucial intermediates (*CHOHCO) is attributed to the upshift of the d-band center of ultra-thin CGS/GS. The C–C coupling barrier is intrinsically reduced by the dominant exposed Cu atoms on the 2D ultra-thin CuGaS₂/Ga₂S₃ in the process of photocatalytic CO₂ reduction, which captures *CO molecules effectively. This study proposes a new strategy to design photocatalyst through defect engineering to adjust the selectivity of photocatalytic CO₂ reduction.     

Highly Boosted Reaction Kinetics in Carbon Dioxide Electroreduction by Surface-Introduced Electronegative Dopants

Effectively improving the selectivity while reducing the overpotential over the electroreduction of CO₂ (CO₂ER) has been challenging. Herein, electronegative N atoms and coordinatively unsaturated Ni N₃ moieties co-anchored carbon nanofiber (Ni N₃ NCNFs) catalyst via an integrated electrospinning and carbonization strategy are reported. The catalyst exhibits a maximum CO Faradaic efficiency (F.E.) of 96.6%, an onset potential of −0.3 V, and a low Tafel slope of 71 mV dec⁻¹ along with high stability over 100 h. Aberration corrected scanning transmission electron microscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy identify the atomically dispersed Ni N₃ sites with Ni atom bonded by three pyridinic N atoms. The existence of abundant electronegative N dopants adjoin the Ni N₃ centers in Ni N₃ NCNFs. Theoretical calculations reveal that both, the undercoordinated Ni N₃ centers and their first neighboring C atoms modified by extra N dopants, display the positive effect on boosting CO₂ adsorption and water dissociation processes, thus accelerating the CO₂ER kinetics process. Furthermore, a designed Zn CO₂ battery with the cathode of Ni N₃ NCNFs delivers a maximum power density of 1.05 mW cm⁻² and CO F.E. of 96% during the discharge process, thus providing a promising approach to electric energy output and chemical conversion.     

Metastable Phase Cu with Optimized Local Electronic State for Efficient Electrocatalytic Production of Ammonia from Nitrate

Electrocatalytic nitrate (NO₃⁻) reduction reaction (NITRR) is an inspiring route for ammonia (NH₃) synthesis at ambient condition. The metallic Cu-based material with low cost and high activity is one of the most promising electrocatalysts for NITRR. However, due to the weaker atomic H^*-providing capacity, the produced intermediate—nitrite tends to accumulate on its surface, leading to unsatisfactory NH₃ selectivity and Faradic efficiency (FE). Herein, a novel and facile O₂/Ar plasma oxidation and subsequent electro-reduction strategy is developed to synthesize a kind of metastable phase Cu. Excitingly, the metastable phase Cu demonstrates superior NITRR performance to conventional phase Cu with high NH₄⁺ selectivity (97.8%) and FE (99.8%). Density function theory (DFT) calculations reveal that the upshift of the d-band center to near the Fermi level in metastable phase Cu contributes to the enhanced activity, while the relatively strong adsorption of H^* facilitates the conversion from NO₂^*/NO^* to NOOH^*/NOH^* and thus ensures high selectivity and FE. Furthermore, when evaluated as cathode material in Zn-NO₃⁻ battery, high power density (7.56 mW cm⁻²) and NH₄⁺ yield (76 µmol h⁻¹ cm⁻²) are achieved by the metastable phase Cu-based battery.     

Proton Turnover Dominated Cascade Route for CO2 Photoreduction

Photoreduction carbon dioxide (CO₂) and water (H₂O) into valuable chemicals is a huge potential to mitigate immoderate CO₂ emissions and energy crisis. To date, tremendous attention is concentrated on the improvement of independent CO₂ reduction or H₂O oxidation behaviors. However, the simultaneous control of efficient electron and hole utilization is still a huge challenge due to the complex cascade redox reactions. Here, a proton turnover exists in the whole CO₂ photoreduction process is discovered, which is defined as the pivot to concatenate the hole and electron behaviors. As a demonstration of the concept, the efficient activated hydrogen (*H) production centers of copper (Cu) and rapid hydrogenation centers of nickel (Ni) are coupled by an alloying strategy, and the proton turnover behaviors could be directly determined by adjustment of the molar ratios of Cu_xNi_y. Moreover, Cu₃Ni₁–TiO₂ exhibits the highest electron selectivity of 93.7% for methane (CH₄) production with a rate of 175.9 µmol g⁻¹ h⁻¹, while Cu₁Ni₅–TiO₂ reaches up to the highest carbon monoxide (CO) electron selectivity and generation rate at 84.4% and 164.6 µmol g⁻¹ h⁻¹, respectively. Consequently, the experimental and theoretical analysis all clarify the predominate proton turnover effect during the overall CO₂ photoreduction process, which directly determines the categories and generated efficiency of C-based products by regulating variable reaction pathways. Therefore, the revelation of the proton turnover pivot could broaden the new sights by bidirectional optimization of dynamics during the overall CO₂ photoreduction system, which favors the efficient, selective, and stable photocatalytic CO₂ reduction with H₂O.     

Dual-Engineering of Porous Structure and Carbon Edge Enables Highly Selective H2O2 Electrosynthesis

Edge engineering has emerged as a powerful strategy to activate inert carbon surfaces, and thus achieve a notable enhanced electrocatalytic activity. However, the rational manipulation of carbon edges to achieve enhanced catalytic performance remains a formidable challenge, primarily hindered by immature synthesis methods and the obscured understanding of the structure-activity relationship. Herein, an organic–inorganic hybrid co-assembly strategy is used to fabricate a series of mesoporous carbon nanofibers (MCNFs) with controllable edge site densities and the impact of edge population on electrochemical oxygen reduction reaction (ORR) pathways is investigated. The optimized MCNFs catalyst exhibits a remarkable 2e⁻ ORR performance, as evidenced by a high H₂O₂ selectivity (>90%) across a wide potential window of 0.6 V and a large cathodic current density of −3.0 mA cm⁻² (at 0.2 V vs. reversible hydrogen electrode). Strikingly, the density of carbon edge sites can be changed to tune the ORR activity and selectivity. Experimental validation and density functional theory calculations confirm that the presence of edge defects can optimize the adsorption strength of *OOH intermediates and balance the selectivity and activity of the 2e⁻ ORR process. This study provides a new path to achieve high ORR activity and 2e⁻ selectivity in carbon-based electrocatalysts.     

Fe?N4O?C Nanoplates Covalently Bonding on Graphene for Efficient CO2 Electroreduction and Zn?CO2 Batteries (Adv. Funct. Mater. 27/2023)

Electrochemical carbon dioxide (CO₂) reduction into value-added products holds great promise in moving toward carbon neutrality but remains a grand challenge due to lack of efficient electrocatalysts. Herein, the nucleophilic substitution reaction is elaborately harnessed to synthesize carbon nanoplates with a Fe N₄O configuration anchored onto graphene substrate (Fe N₄O C/Gr) through covalent linkages. Density functional theory calculations demonstrate the unique configuration of Fe N₄O with one oxygen (O) atom in the axial direction not only suppresses the competing hydrogen evolution reaction, but also facilitates the desorption of *CO intermediate compared with the commonly planar single-atomic Fe sites. The Fe N₄O C/Gr shows excellent performance in the electroreduction of CO₂ into carbon monoxide (CO) with an impressive Faradaic efficiency of 98.3% at −0.7 V versus reversible hydrogen electrode (RHE) and a high turnover frequency of 3511 h⁻¹. Furthermore, as a cathode catalyst in an aqueous zinc (Zn)-CO₂ battery, the Fe N₄O C/Gr achieves a high CO Faradaic efficiency (≈91%) at a discharge current density of 3 mA cm⁻² and long-term stability over 74 h. This work opens up a new route to simultaneously modulate the geometric and electronic structure of single-atomic catalysts toward efficient CO₂ conversion.     

Hybrid Catalyst Coupling Zn Single Atoms and CuNx Clusters for Synergetic Catalytic Reduction of CO2

Reverse water-gas shift (RWGS) reaction is the initial and necessary step of CO₂ hydrogenation to high value-added products, and regulating the selectivity of CO is still a fundamental challenge. In the present study, an efficient catalyst (CuZnN_x@C-N) composed by Zn single atoms and Cu clusters stabilized by nitrogen sites is reported. It contains saturated four-coordinate Zn-N₄ sites and low valence CuN_x clusters. Monodisperse Zn induces the aggregation of pyridinic N to form Zn-N₄ and N₄ structures, which show strong Lewis basicity and has strong adsorption for *CO₂ and *COOH intermediates, but weak adsorption for *CO, thus greatly improves the CO₂ conversion and CO selectivity. The catalyst calcined at 700 °C exhibits the highest CO₂ conversion of 43.6% under atmospheric pressure, which is 18.33 times of Cu-ZnO and close to the thermodynamic equilibrium conversion rate (49.9%) of CO₂. In the catalytic process, CuN_x not only adsorbs and activates H₂, but also cooperates with the adjacent Zn-N₄ and N₄ structures to jointly activate CO₂ molecules and further promotes the hydrogenation of CO₂. This synergistic mechanism will provide new insights for developing efficient hydrogenation catalysts.     

In Situ Formed “Sn1–XInX@In1–YSnYOZ” Core@Shell Nanoparticles as Electrocatalysts for CO2 Reduction to Formate

Electrochemical reduction of CO₂ (CO₂RR) driven by renewable energy has gained increasing attention for sustainable production of chemicals and fuels. Catalyst design to overcome large overpotentials and poor product selectivity remains however challenging. Sn/SnOx and In/InOx composites have been reported active for CO₂RR with high selectivity toward formate formation. In this work, the CO₂RR activity and selectivity of metal/metal oxide composite nanoparticles formed by in situ reduction of bimetallic amorphous SnInOx thin films are investigated. It is shown that during CO₂RR the amorphous SnInOx pre-catalyst thin films are reduced in situ into Sn_1–XIn_X@In_1–YSn_YO_z core@shell nanoparticles composed of Sn-rich SnIn alloy nanocores (with x < 0.2) surrounded by InOx-rich bimetallic InSnOx shells (with 0.3 < y < 0.4 and z ≈ 1). The in situ formed particles catalyze the CO₂RR to formate with high faradaic efficiency (80%) and outstanding formate mass activity (437 A g_In+Sn⁻¹ @ −1.0 V vs RHE in 0.1 m KHCO₃). While extensive structural investigation during CO₂RR reveals pronounced dynamics in terms of particle size, the core@shell structure is observed for the different electrolysis conditions essayed, with high surface oxide contents favoring formate over hydrogen selectivity.     

Unveiling Role of Sulfate Ion in Nickel-Iron (oxy)Hydroxide with Enhanced Oxygen-Evolving Performance

The rational design of effective catalysts for sluggish oxygen evolution reactions (OERs) is desired but challenging. Nickel-iron (NiFe) (oxy)hydroxides are promising pre-electrocatalysts for alkaline OER. However, OER performances are limited by the slow reconstruction process to generate active species of high-valance NiFe oxyhydroxides. In this work, a sulfate ion (SO₄²⁻) modulated strategy is developed to boost the OER activity of NiFe (oxy)hydroxide by accelerating the electrochemical reconstruction of pre-catalyst and stabilizing the reaction intermediate of OOH* during OER. The SO₄²⁻ decorated NiFe (oxy)hydroxide catalyst (NF-S0.15) is fabricated via scalable anodization of NiFe foam in a thiourea-dissolved electrolyte. The experimental and theoretical investigations demonstrate the dual effect of SO₄²⁻ on improving OER performances. SO₄²⁻ leaching is favorable for the electrochemical reconstruction to form active NiFeOOH under OER condition. Simultaneously, the residual SO₄²⁻ adsorbed on surface can stabilize the intermediate of OOH*, and thus enhance the OER performances. As expected, NF-S0.15 delivers an ultralow overpotential of 234 mV to reach the current density of 50 mA cm⁻², a fast OER kinetics (27.7 mV dec⁻¹), and a high stability for more than 100 h. This unique insights into anionic modification could inspire the development of advanced electrocatalysts for efficient OER.