Wood-Structured Nanomaterials as Highly Efficient, Self-Standing Electrocatalysts for Water Splitting

Electrocatalytic water splitting (EWS) driven by renewable energy is widely considered an environmentally friendly and sustainable approach for generating hydrogen (H2), an ideal energy carrier for the future. However, the efficiency and economic viability of large-scale water electrolysis depend on electrocatalysts that can efficiently accelerate the electrochemical reactions taking place at the two electrodes. Wood-derived nanomaterials are well-suited for serving as EWS catalysts because of their hierarchically porous structure with high surface area and low tortuosity, compositional tunability, cost-effectiveness, and self-standing integral electrode configuration. Here, recent advancements in the design and synthesis of wood-structured nanomaterials serving as advanced electrocatalysts for water splitting are summarized. First, the design principles and corresponding strategies toward highly effective wood-structured electrocatalysts (WSECs) are emphasized. Then, a comprehensive overview of current findings on WSECs, encompassing diverse structural designs and functionalities such as supported-metal nanoparticles (NPs), single-atom catalysts (SACs), metal compounds, and heterostructured electrocatalysts based on engineered wood hosts are presented. Subsequently, the application of these WSECs in various aspects of water splitting, including the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), overall water splitting (OWS), and hybrid water electrolysis (HWE) are explored. Finally, the prospects, challenges, and opportunities associated with the broad application of WSECs are briefly discussed. This review aims to provide a comprehensive understanding of the ongoing developments in water-splitting catalysts, along with outlining design principles for the future development of WSECs.

Self-Supporting Bi-Sb Bimetallic Nanoleaf for Electrochemical Synthesis of Formate by Highly Selective CO2 Reduction

Electrocatalytic reduction of CO₂ into valuable fuels and chemical feedstocks in a sustainable and environmentally friendly manner is an ideal way to mitigate climate change and environmental problems. Here, we fabricated a series of self-supporting Bi-Sb bimetallic nanoleaves on carbon paper (CP) by a facile electrodeposition method. The synergistic effect of Bi and Sb components and the change of the electronic structure lead to high formate selectivity and excellent stability in the electrochemical CO₂ reduction reaction (CO₂RR). Specifically, the Bi-Sb/CP bimetallic electrode achieved a high Faradic efficiency (FE_formate, 88.30%) at -0.9 V (vs RHE). The FE of formate remained above 80% in a broad potential range of -0.9 to -1.3 V (vs RHE), while FE_CO was suppressed below 6%. Density functional theory calculations showed that Bi(012)-Sb reduced the adsorption energy of the *OCHO intermediate and promoted the mass transfer of charges. The optimally adsorbed *OCHO intermediate promoted formate production while inhibiting the CO product pathway, thereby enhancing the selectivity to formate synthesis. Moreover, the CO₂RR performance was also investigated in a flow-cell system to evaluate its potential for industrial applications. The bimetallic Bi-Sb catalyst can maintain a steady current density of 160 mA/cm² at -1.2 V (vs RHE) for 25 h continuous electrolysis. Such excellent stability for formate generation in flow cells has rarely been reported in previous studies. This work offers new insights into the development of bimetallic self-supporting electrodes for CO₂ reduction.

Ni single atoms supported on hierarchically porous carbonized wood with highly active Ni-N4 sites as a self-supported electrode for superior CO2 electroreduction

Powdery N-doped carbon-supported single-atom catalysts (SACs) can be prepared on a large scale and are highly selective in converting CO₂ to CO, but their practical application is restricted by their powdery texture. Herein, we report Ni single atoms supported on hierarchically porous N-doped carbonized wood (Ni SAs-NCW) as a self-supported electrode for efficient and durable CO₂ electroreduction. The porous NCW matrix possesses an abundance of open aligned microchannels that allow unimpeded CO₂ diffusion and electrolyte transportation while the uniformly dispersed Ni SAs in the NCW matrix in the Ni-N₄ configuration afford ample highly active sites for CO₂ electroreduction. This Ni SAs-NCW electrode exhibits a high CO₂-to-CO faradaic efficiency (FE_CO) of 92.1% and a CO partial current density (j_CO) of 11.4 mA cm^-2 at -0.46 V versus the reversible hydrogen electrode (RHE) and maintains a stable FE_CO and j_CO over a period of 9 h of electrolysis. This work provides an effective strategy to develop efficient SACs with potential to be integrated into flow cell systems for large-scale CO₂ reduction.

NiFe-CN catalysts derived from Solid-phase Exfoliation of NiFe-Layered Double Hydroxide for CO2 Electroreduction

The development of efficient carbon dioxide reducing reaction (CO2RR) catalysts is one of the practical solutions to environmental problems. Usually metal-doped catalysts were used for CO2RR, but the metal elements...

Carbonized wood membrane decorated with AuPd alloy nanoparticles as an efficient self-supported electrode for electrocatalytic CO2 reduction

Efficient electrocatalytic reduction of CO₂ to value-added chemicals and fuels is a promising technology for mitigating energy shortage and pollution issues yet highly relay on the development of high-performance electrocatalysts. Herein, we develop an effective strategy to fabricate carbonized wood membrane (CW) decorated with AuPd alloy nanoparticles with tunable composition (termed as AuPd@CW) as self-supported electrodes for efficient electrocatalytic CO₂ reduction. The uniformly distributed AuPd nanoparticles on wood matrix are first achieved through the in-situ reduction of metal cations by the lignin content in wood. Subsequently, two-step carbonization was employed to promote the alloying of AuPd nanoparticles and the formation of CW. The AuPd@CW membrane electrode features an integrated macroscopic structure with numerous open and aligned channels for rapid electron transfer and mass diffusion and well-dispersed AuPd alloy nanoparticles as active sites for the CO₂ reduction. The optimal Au₉₅Pd₅@CW electrode affords a high selectivity for CO₂ electroreduction with a maximum CO faradaic efficiency (FE_CO) of 82% at an overpotential of 0.49 V, much higher than those obtained on Au@CW and Pd@CW electrodes. The CO current density and FE_CO remain relatively stable during a 12 h electrolysis reaction. In addition, density functional theory (DFT) calculations reveal that alloying Au with Pd enables a balance between the formation of intermediate COOH* and the desorption of CO on the surface of AuPd nanoparticles, thus enhancing the selectivity of CO production. This work offers an effective strategy for the fabrication of bimetallic alloys supported on wood-based carbon membrane as a practical electrode for electrochemical energy conversion.

From CO2 to Value-Added Products: A Review about Carbon-Based Materials for Electro-Chemical CO2 Conversion

The global warming and the dangerous climate change arising from the massive emission of CO2 from the burning of fossil fuels have motivated the search for alternative clean and sustainable energy sources. However, the industrial development and population necessities make the decoupling of economic growth from fossil fuels unimaginable and, consequently, the capture and conversion of CO2 to fuels seems to be, nowadays, one of the most promising and attractive solutions in a world with high energy demand. In this respect, the electrochemical CO2 conversion using renewable electricity provides a promising solution. However, faradaic efficiency of common electro-catalysts is low, and therefore, the design of highly selective, energy-efficient, and cost-effective electrocatalysts is critical. Carbon-based materials present some advantages such as relatively low cost and renewability, excellent electrical conductivity, and tunable textural and chemical surface, which show them as competitive materials for the electro-reduction of CO2. In this review, an overview of the recent progress of carbon-based electro-catalysts in the conversion of CO2 to valuable products is presented, focusing on the role of the different carbon properties, which provides a useful understanding for the materials design progress in this field. Development opportunities and challenges in the field are also summarized.

Tobacco stem-derived nitrogen-containing porous carbon with highly dispersed Ni–N sites as an efficient electrocatalyst for CO2 reduction to CO

A cost-effective electrocatalyst with highly dispersed Ni–N sites was prepared by tobacco stem-derived nitrogen-containing porous carbon.

Recent Advances in the Electroreduction of CO2 over Heteroatom-Doped Carbon Materials

Ever-growing anthropogenic activity has increased global energy demands, resulting in growing concentrations of greenhouse gases such as CO2 in the atmosphere. The electroreduction of CO2 has been proposed as a potential solution for reducing anthropogenic CO2 emissions. Despite the promising results obtained so far, some limitations hinder large-scale applications, especially those associated with the activity and selectivity of electrocatalysts. A good number of metal catalysts have been studied to overcome this limitation, but the high cost and low earth abundance of some of these materials are important barriers. In this sense, carbon materials doped with heteroatoms such as N, B, S, and F have been proposed as cheaper and widely available alternatives to metal catalysts. This review summarizes the latest advances in the utilization of carbon-doped materials for the electroreduction of CO2, with a particular emphasis on the synthesis procedures and the electrochemical performance of the resulting materials.