Advances and challenges in the electrochemical reduction of carbon dioxide.

The electrocatalytic carbon dioxide reduction reaction (ECO2RR) is a promising way to realize the transformation of waste into valuable material, which can not only meet the environmental goal of reducing carbon emissions, but also obtain clean energy and valuable industrial products simultaneously. Herein, we first introduce the complex CO2RR mechanisms based on the number of carbons in the product. Since the coupling of C-C bonds is unanimously recognized as the key mechanism step in the ECO2RR for the generation of high-value products, the structural-activity relationship of electrocatalysts is systematically reviewed. Next, we comprehensively classify the latest developments, both experimental and theoretical, in different categories of cutting-edge electrocatalysts and provide theoretical insights on various aspects. Finally, challenges are discussed from the perspectives of both materials and devices to inspire researchers to promote the industrial application of the ECO2RR at the earliest.

Synergistic Promotion of Large-Current Water Splitting through Interfacial Engineering of Hierarchically Structured CoP-FeP Nanosheets with Rich P Vacancies.

The development of hydrogen evolution reaction (HER) catalysts with high performance under large current density is still a challenge. Introducing P vacancies in heterostructure is an appealing strategy to enhance HER kinetics. This study investigates a CoP-FeP heterostructure catalyst with abundant P vacancies (Vp-CoP-FeP/NF) on nickel foam (NF), which was prepared using dipping and phosphating treatment. The optimized Vp-CoP-FeP catalyst exerted prominent HER catalytic capability, requiring an ultra-low overpotential (58 mV @ 10 mA cm-2 ) and displaying robust durability (50 h @ 200 mA cm-2 ) in 1.0 M KOH solution. Furthermore, the catalyst demonstrated superior overall water splitting activity as cathode, demanding only cell voltage of 1.76 V at 200 mA cm-2 , outperforming Pt/C/NF(-) || RuO2 /NF(+) . The catalyst's outstanding performance can be attributed to the hierarchical structure of porous nanosheets, abundant P vacancies, and synergistic effect between CoP and FeP components, which promote water dissociation and H* adsorption and desorption, thereby synergically accelerating HER kinetics and enhancing HER activity. This study demonstrates the potential of HER catalysts with phosphorus-rich vacancies that can work under industrial-scale current density, highlighting the importance of developing durable and efficient catalysts for hydrogen production.

Nanowire-structured FeP-CoP arrays as highly active and stable bifunctional electrocatalyst synergistically promoting high-current overall water splitting.

The design and construction of highly efficient and durable non-noble metal bifunctional catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media is essential for developing the hydrogen economy. To achieve this goal, we have developed a bifunctional nanowire-structured FeP-CoP array catalyst on carbon cloth with uniform distribution through in-situ hydrothermal growth and phosphating treatment. The unique nanowire array structure and the strong electronic interaction between FeP and CoP species have been confirmed. Electrochemical studies have found that the designed Fe0.14Co0.86-P/CC catalyst appears excellent HER (130 mV@10 mA cm-2)/OER (270 mV@10 mA cm-2) activity and stability. Moreover, the bifunctional Fe0.14Co0.86-P/CC(+/-) catalyst is also used in simulated industrial water splitting system, where the pair catalyst requires about 1.95 and 2.14 V to reach 500 and 1000 mA cm-2, even superior to the control RuO2(+)||Pt/C(-) catalyst, showing good industrial application prospects. These excellent electrocatalytic properties are attributed to the synergy between FeP and CoP species as well as the unique microstructure, which can accelerate charge transfer, expose more active sites and enhance electrolyte diffusion and gas emissions.

Interface Engineering of Needle-Like P-Doped MoS2 /CoP Arrays as Highly Active and Durable Bifunctional Electrocatalyst for Overall Water Splitting.

Developing a bifunctional water splitting catalyst with high efficiency and low cost are crucial in the electrolysis water industry. Here, we report a rational design and simple preparation method of MoS2 -based bifunctional electrocatalyst on carbon cloth (CC). The optimized P-doped MoS2 @CoP/CC catalyst presents low overpotentials for the hydrogen (HER) and oxygen evolution reactions (OER) of 64 and 282 mV in alkaline solution as well as 72 mV HER overpotential in H2 SO4 at a current density of 10 mA cm-2 . Furthermore, P-MoS2 @CoP/CC as a bifunctional catalyst delivered relatively low cell voltages of 1.83 and 1.97 V at high current densities of 500 and mA cm-2 in 30 % KOH. The two-electrode system showed a remarkable stability for 30 h, even outperformed the benchmark RuO2 ||Pt/C catalyst. The excellent electrochemical performance can be credited to the unique microstructure, high surface area, and the synergy between metal species. This study presents a possible alternative for noble metal-based catalysts to overcome the challenges of industrial applications.