Semiconductive Copper(I)–Organic Frameworks for Efficient Light‐Driven Hydrogen Generation Without Additional Photosensitizers and Cocatalysts

As the first example of a photocatalytic system for splitting water without additional cocatalysts and photosensitizers, the comparatively cost‐effective Cu₂I₂‐based MOF, Cu‐I‐bpy (bpy=4,4′‐bipyridine) exhibited highly efficient photocatalytic hydrogen production (7.09 mmol g⁻¹ h⁻¹). Density functional theory (DFT) calculations established the electronic structures of Cu‐I‐bpy with a narrow band gap of 2.05 eV, indicating its semiconductive behavior, which is consistent with the experimental value of 2.00 eV. The proposed mechanism demonstrates that Cu₂I₂ clusters of Cu‐I‐bpy serve as photoelectron generators to accelerate the copper(I) hydride interaction, providing redox reaction sites for hydrogen evolution. The highly stable cocatalyst‐free and self‐sensitized Cu‐I‐bpy provides new insights into the future design of cost‐effective d¹⁰‐based MOFs for highly efficient and long‐term solar fuels production.     

Surfactant‐Assisted Phase‐Selective Synthesis of New Cobalt MOFs and Their Efficient Electrocatalytic Hydrogen Evolution Reaction

Reported herein are two new polymorphic Co‐MOFs (CTGU‐5 and ‐6) that can be selectively crystallized into the pure 2D or 3D net using an anionic or neutral surfactant, respectively. Each polymorph contains a H₂O molecule, but differs dramatically in its bonding to the framework, which in turn affects the crystal structure and electrocatalytic performance for hydrogen evolution reaction (HER). Both experimental and computational studies find that 2D CTGU‐5 which has coordinates water and more open access to the cobalt site has higher electrocatalytic activity than CTGU‐6 with the lattice water. The integration with co‐catalysts, such as acetylene black (AB) leads to a composite material, AB&CTGU‐5 (1:4) with very efficient HER catalytic properties among reported MOFs. It exhibits superior HER properties including a very positive onset potential of 18 mV, low Tafel slope of 45 mV dec⁻¹, higher exchange current density of 8.6×10⁻⁴ A cm⁻², and long‐term stability.     

From a Molecular 2Fe‐2Se Precursor to a Highly Efficient Iron Diselenide Electrocatalyst for Overall Water Splitting

A highly active FeSe₂ electrocatalyst for durable overall water splitting was prepared from a molecular 2Fe‐2Se precursor. The as‐synthesized FeSe₂ was electrophoretically deposited on nickel foam and applied to the oxygen and hydrogen evolution reactions (OER and HER, respectively) in alkaline media. When used as an oxygen‐evolution electrode, a low 245 mV overpotential was achieved at a current density of 10 mA cm⁻², representing outstanding catalytic activity and stability because of Fe(OH)₂/FeOOH active sites formed at the surface of FeSe₂. Remarkably, the system is also favorable for the HER. Moreover, an overall water‐splitting setup was fabricated using a two‐electrode cell, which displayed a low cell voltage and high stability. In summary, the first iron selenide material is reported that can be used as a bifunctional electrocatalyst for the OER and HER, as well as overall water splitting.     

Broadband Light Harvesting and Unidirectional Electron Flow for Efficient Electron Accumulation for Hydrogen Generation

The efficiency of solar hydrogen evolution closely depends on the multiple electrons accumulation on the catalytic center for two‐electron‐involved water reduction. Herein, we report an effective approach to enable broadband light absorption and unidirectional electron flow for efficiently accumulating electrons at active sites for hydrogen evolution by rationally engineering the nanostructure of Pt nanoparticles (NPs), TiO₂, and SiO₂ support. In addition to Schottky‐junction‐driven electron transfer from TiO₂ to Pt, Pt NPs also produce hot electrons by recycling the scattered visible and near‐infrared (vis‐NIR) light of the support. Unidirectional electron flow to active sites is realized by tuning the components spatial distribution. These features collectively accumulate multiple electrons at catalytic Pt sites, thereby affording enhanced activity toward hydrogen evolution under simulated sunlight.     

Engineering the Coordination Environment of Single‐Atom Platinum Anchored on Graphdiyne for Optimizing Electrocatalytic Hydrogen Evolution

Two Pt single‐atom catalysts (SACs) of Pt‐GDY1 and Pt‐GDY2 were prepared on graphdiyne (GDY)supports. The isolated Pt atoms are dispersed on GDY through the coordination interactions between Pt atoms and alkynyl C atoms in GDY, with the formation of five‐coordinated C₁‐Pt‐Cl₄ species in Pt‐GDY1 and four‐coordinated C₂‐Pt‐Cl₂ species in Pt‐GDY2. Pt‐GDY2 shows exceptionally high catalytic activity for the hydrogen evolution reaction (HER), with a mass activity up to 3.3 and 26.9 times more active than Pt‐GDY1 and the state‐of‐the‐art commercial Pt/C catalysts, respectively. Pt‐GDY2 possesses higher total unoccupied density of states of Pt 5d orbital and close to zero value of Gibbs free energy of the hydrogen adsorption (|Δ |) at the Pt active sites, which are responsible for its excellent catalytic performance. This work can help better understand the structure–catalytic activity relationship in Pt SACs.     

An Efficient,Visible‐Light‐Driven,Hydrogen Evolution Catalyst NiS/ZnxCd1−xS Nanocrystal Derived from a Metal–Organic Framework

Photocatalytic water splitting for hydrogen production using sustainable sunlight is a promising alternative to industrial hydrogen production. However, the scarcity of highly active, recyclable, inexpensive photocatalysts impedes the development of photocatalytic hydrogen evolution reaction (HER) schemes. Herein, a metal–organic framework (MOF)‐template strategy was developed to prepare non‐noble metal co‐catalyst/solid solution heterojunction NiS/Zn_xCd_1−xS with superior photocatalytic HER activity. By adjusting the doping metal concentration in MOFs, the chemical compositions and band gaps of the heterojunctions can be fine‐tuned, and the light absorption capacity and photocatalytic activity were further optimized. NiS/Zn_0.5Cd_0.5S exhibits an optimal HER rate of 16.78 mmol g⁻¹ h⁻¹ and high stability and recyclability under visible‐light irradiation (λ>420 nm). Detailed characterizations and in‐depth DFT calculations reveal the relationship between the heterojunction and photocatalytic activity and confirm the importance of NiS in accelerating the water dissociation kinetics, which is a crucial factor for photocatalytic HER.     

Rational Design of Single Molybdenum Atoms Anchored on N‐Doped Carbon for Effective Hydrogen Evolution Reaction

The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising pathway to resolve energy and environment problems. An electrocatalyst was designed with single Mo atoms (Mo‐SAs) supported on N‐doped carbon having outstanding HER performance. The structure of the catalyst was probed by aberration‐corrected scanning transmission electron microscopy (AC‐STEM) and X‐ray absorption fine structure (XAFS) spectroscopy, indicating the formation of Mo‐SAs anchored with one nitrogen atom and two carbon atoms (Mo₁N₁C₂). Importantly, the Mo₁N₁C₂ catalyst displayed much more excellent activity compared with Mo₂C and MoN, and better stability than commercial Pt/C. Density functional theory (DFT) calculation revealed that the unique structure of Mo₁N₁C₂ moiety played a crucial effect to improve the HER performance. This work opens up new opportunities for the preparation and application of highly active and stable Mo‐based HER catalysts.