Observation on Microenvironment Changes of Dynamic Catalysts in Acidic CO2 Reduction.

Electrochemical CO2 reduction reaction (CO2RR) in acid can solve alkalinity issues while highly corrosive and reductive acidic electrolytes usually cause catalyst degradation. Inhibiting catalyst degradation is crucial for the stability of acidic CO2RR. Here, we reveal the microenvironment changes of dynamic Bi-based catalysts and develop a pulse chronoamperometry (CA) strategy to improve the stability of acidic CO2RR. In situ fluorescence mappings show that the local pH changes from neutral to acid, and the in situ Raman spectra reveal the dynamic evolution of interfacial water structures in the microenvironment. We propose that the surface charge properties of dynamic catalysts affect the competitive adsorption of K+ and protons, thereby causing the differences in local pH and CO2RR intermediate adsorption. We also develop a pulse CA strategy to reactivate catalysts, and the stability of acidic CO2RR is improved by 2 orders of magnitude for 100 h operation, which is higher than most reports on the stability of acidic CO2RR. This work gives insights on how microenvironment changes affecting the stability of acidic CO2RR, and provides guidance for designing stable catalysts in acidic electrolytes.

Ampere-Level Current Density CO2 Reduction with High C2+ Selectivity on La(OH)3-Modified Cu Catalysts.

The carbon dioxide reduction reaction (CO2RR) driven by electricity can transform CO2 into high-value multi-carbon (C2+) products. Copper (Cu)-based catalysts are efficient but suffer from low C2+ selectivity at high current densities. Here La(OH)3 in Cu catalyst is introduced to modify its electronic structure towards efficient CO2RR to C2+ products at ampere-level current densities. The La(OH)3/Cu catalyst has a remarkable C2+ Faradaic efficiency (FEC2+) of 71.2% which is 2.2 times that of the pure Cu catalyst at a current density of 1,000 mA cm-2 and keeps stable for 8 h. In situ spectroscopy and density functional theory calculations both show that La(OH)3 modifies the electronic structure of Cu. This modification favors *CO adsorption, subsequent hydrogenation, *CO─*COH coupling, and consequently increases C2+ selectivity. This work provides a guidance on facilitating C2+ product formation, and suppressing hydrogen evolution by La(OH)3 modification, enabling efficient CO2RR at ampere-level current densities.

Multiscale Confinement Engineering for Boosting Overall Water Splitting by One-Step Stringing of a Single Atom and a Janus Nanoparticle within a Carbon Nanotube.

Enzyme-mimicking confined catalysis has attracted great interest in heterogeneous catalytic systems that can regulate the geometric or electronic structure of the active site and improve its performance. Herein, a liquid-assisted chemical vapor deposition (LCVD) strategy is proposed to simultaneously confine the single-atom Ru sites onto sidewalls and Janus Ni/NiO nanoparticles (NPs) at the apical nanocavities to thoroughly energize the N-doped carbon nanotube arrays (denoted as Ni/NiO@Ru-NC). The bifunctional Ni/NiO@Ru-NC electrocatalyst exhibits overpotentials of 88 and 261 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at 100 mA cm-2 in alkaline solution, respectively, all ranking the top tier among the carbon-supported metal-based electrocatalysts. Moreover, once integrated into an anion-exchange membrane water electrolysis (AEMWE) system, Ni/NiO@Ru-NC can act as an efficient and robust bifunctional electrocatalyst to operate stably for 50 h under 500 mA cm-2. Theoretical calculations and experimental exploration demonstrate that the confinement of Ru single atoms and Janus Ni/NiO NPs can regulate the electron distribution with strong orbital couplings to activate the NC nanotube from sidewall to top, thus boosting overall water splitting.

A corrosion-resistant RuMoNi catalyst for efficient and long-lasting seawater oxidation and anion exchange membrane electrolyzer.

Direct seawater electrolysis is promising for sustainable hydrogen gas (H2) production. However, the chloride ions in seawater lead to side reactions and corrosion, which result in a low efficiency and poor stability of the electrocatalyst and hinder the use of seawater electrolysis technology. Here we report a corrosion-resistant RuMoNi electrocatalyst, in which the in situ-formed molybdate ions on its surface repel chloride ions. The electrocatalyst works stably for over 3000 h at a high current density of 500 mA cm-2 in alkaline seawater electrolytes. Using the RuMoNi catalyst in an anion exchange membrane electrolyzer, we report an energy conversion efficiency of 77.9% and a current density of 1000 mA cm-2 at 1.72 V. The calculated price per gallon of gasoline equivalent (GGE) of the H2 produced is $ 0.85, which is lower than the 2026 technical target of $ 2.0/GGE set by the United Stated Department of Energy, thus, suggesting practicability of the technology.

Two-Dimensional Metal Coordination Polymer Derived Indium Nanosheet for Efficient Carbon Dioxide Reduction to Formate.

Main group indium materials have been known as promising electrocatalysts for two-electron-involved carbon dioxide reduction to produce formate, which is a key energy vector in many industrial reactions. However, the synthesis of two-dimensional (2D) monometallic nonlayered indium remains a great challenge. Here, we present a facile electrochemical reduction strategy to transform 2D indium coordination polymer into elemental indium nanosheets. In a customized flow cell, the reconstructed metallic indium exhibits a high Faradaic efficiency (FE) of 96.3% for formate with a maximum partial current density exceeding 360 mA cm-2 and negligible degradation after 140 h operation in 1 M KOH solution, outperforming the state-of-the-art indium-based electrocatalysts. Moreover, in and ex situ electrochemical analysis and characterizations demonstrate that the enhanced exposure of active sites and mass/charge transport at the CO2 gas-catalyst-electrolyte triple-phase interface and the restrained electrolyte flooding are contributing to producing and stabilizing carbon dioxide radical anion intermediates, thus leading to superior catalytic performance.

Dual interfacial engineering of a Chevrel phase electrode material for stable hydrogen evolution at 2500 mA cm-2.

Constructing stable electrodes which function over long timescales at large current density is essential for the industrial realization and implementation of water electrolysis. However, rapid gas bubble detachment at large current density usually results in peeling-off of electrocatalysts and performance degradation, especially for long term operations. Here we construct a mechanically-stable, all-metal, and highly active CuMo6S8/Cu electrode by in-situ reaction between MoS2 and Cu. The Chevrel phase electrode exhibits strong binding at the electrocatalyst-support interface with weak adhesion at electrocatalyst-bubble interface, in addition to fast hydrogen evolution and charge transfer kinetics. These features facilitate the achievement of large current density of 2500 mA cm-2 at a small overpotential of 334 mV which operate stably at 2500 mA cm-2 for over 100 h. In-situ total internal reflection imaging at micrometer level and mechanical tests disclose the relationships of two interfacial forces and performance of electrocatalysts. This dual interfacial engineering strategy can be extended to construct stable and high-performance electrodes for other gas-involving reactions.

Nanostructured metal phosphides: from controllable synthesis to sustainable catalysis.

Metal phosphides (MPs) with unique and desirable physicochemical properties provide promising potential in practical applications, such as the catalysis, gas/humidity sensor, environmental remediation, and energy storage fields, especially for transition metal phosphides (TMPs) and MPs consisting of group IIIA and IVA metal elements. Most studies, however, on the synthesis of MP nanomaterials still face intractable challenges, encompassing the need for a more thorough understanding of the growth mechanism, strategies for large-scale synthesis of targeted high-quality MPs, and practical achievement of functional applications. This review aims at providing a comprehensive update on the controllable synthetic strategies for MPs from various metal sources. Additionally, different passivation strategies for engineering the structural and electronic properties of MP nanostructures are scrutinized. Then, we showcase the implementable applications of MP-based materials in emerging sustainable catalytic fields including electrocatalysis, photocatalysis, mild thermocatalysis, and related hybrid systems. Finally, we offer a rational perspective on future opportunities and remaining challenges for the development of MPs in the materials science and sustainable catalysis fields.

Stress-Transfer-Induced In†Situ Formation of Ultrathin Nickel Phosphide Nanosheets for Efficient Hydrogen Evolution.

Ultrathin two-dimensional (2D) nanostructures have attracted increasing research interest for energy storage and conversion. However, tackling the key problem of lattice mismatch inducing the instability of ulreathin nanostructures during phase transformations is still a critical challenge. Herein, we describe a facile and scalable strategy for the growth of ultrathin nickel phosphide (Ni2 P) nanosheets (NSs) with exposed (001) facets. We show that single-layer functionalized graphene with residual oxygen-containing groups and a large lateral size contributes to reducing the lattice strain during phosphorization. The resulting nanostructure exhibits remarkable hydrogen evolution activity and good stability under alkaline conditions.

Tunable plasmonic core-shell heterostructure design for broadband light driven catalysis.

Considerable effort has been devoted to manipulating the optical absorption of metal nanostructures for diverse applications. However, it still remains a challenge to develop a general and flexible method to promote broadband absorption of metal nanostructures without changing their size and shape. Here, we report a new strategy of hybridizing two conceptually different optical models to realize broadband absorption enhancement of metal nanoparticles (NPs), which is enabled by constructing a core-shell heterostructure, consisting of a spherical dielectric core covered by a metal NPs interlayer and tunable semiconductor shell. This approach integrates the interfacial photon management, photoexcitation of metal NPs and injection of hot charge carriers into the semiconductor shell, and results in distinctly enhanced hot charge carrier generation and transfer, thereby boosting the broad-spectrum light driven catalysis. The structure-plasmon-catalysis interplay of the heterostructure is comprehensively studied and optimized. This proof-of-concept proves to be generally feasible by varying the type of both metal NPs and support medium, opening a new avenue to control the optoelectronic properties of materials.