Constructing a AZO/TiO2 Core/Shell Nanocone Array with Uniformly Dispersed Au NPs for Enhancing Photoelectrochemical Water Splitting

Constructing core/shell nanostructures with optimal structure and composition could maximize the solar light utilization. Here, using an Al nanocone array as a substrate, a well‐defined regular array of AZO/TiO₂ core/shell nanocones with uniformly dispersed Au nanoparticles (AZO/TiO₂/Au NCA) is successfully realized through three sequential steps of atomic layer deposition, physical vapor deposition, and annealing processes. By tuning the structural and compositional parameters, the advantages of light trapping and short carrier diffusion from the core/shell nanocone array, as well as the surface plasmon resonance and catalytic effects from the Au nanoparticles can be maximally utilized. Accordingly, a remarkable photoelectrochemical (PEC) performance can be acquired and the photocurrent density of the AZO/TiO₂/Au NCA electrode reaches up to 1.1 mA cm^?2 at 1.23 V, versus reversible hydrogen electrode (RHE) under simulated sunlight illumination, which is five times that of a flat AZO/TiO₂ electrode (0.22 mA cm^?2). Moreover, the photoconversion of the AZO/TiO₂/Au NCA electrode approaches 0.73% at 0.21 V versus RHE, which is one of the highest values with the lowest applied bias ever reported in Au/TiO₂ PEC composites. These results demonstrate a feasible route toward the scalable fabrication of well‐modulated core/shell nanostructures and can be easily applied to other metal/semiconductor composites for high‐performance PEC.     

Fullerene as a Photoelectron Transfer Promoter Enabling Stable TiO2‐Protected Sb2Se3 Photocathodes for Photo‐Electrochemical Water Splitting

Understanding the degradation mechanisms of photoelectrodes and improving their stability are essential for fully realizing solar‐to‐hydrogen conversion via photo‐electrochemical (PEC) devices. Although amorphous TiO₂ layers have been widely employed as a protective layer on top of p‐type semiconductors to implement durable photocathodes, gradual photocurrent degradation is still unavoidable. This study elucidates the photocurrent degradation mechanisms of TiO₂‐protected Sb₂Se₃ photocathodes and proposes a novel interface‐modification methodology in which fullerene (C₆₀) is introduced as a photoelectron transfer promoter for significantly enhancing long‐term stability. It is demonstrated that the accumulation of photogenerated electrons at the surface of the TiO₂ layer induces the reductive dissolution of TiO₂, accompanied by photocurrent degradation. In addition, the insertion of the C₆₀ photoelectron transfer promoter at the Pt/TiO₂ interface facilitates the rapid transfer of photogenerated electrons out of the TiO₂ layer, thereby yielding enhanced stability. The Pt/C₆₀/TiO₂/Sb₂Se₃ device exhibits a high photocurrent density of 17 mA cm^?2 and outstanding stability over 10 h of operation, representing the best PEC performance and long‐term stability compared with previously reported Sb₂Se₃‐based photocathodes. This research not only provides in‐depth understanding of the degradation mechanisms of TiO₂‐protected photocathodes, but also suggests a new direction to achieve durable photocathodes for photo‐electrochemical water splitting.     

Extended Light Harvesting with Dual Cu2O‐Based Photocathodes for High Efficiency Water Splitting

Cu₂O is one of the most promising light absorbing materials for solar energy conversion. Previous studies with Cu₂O for water splitting usually deliver high photocurrent or high photovoltage, but not both. Here, a Cu₂O/Ga₂O₃/TiO₂/RuO_x photocathode that benefits from a high quality thermally oxidized Cu₂O layer and good band alignment of the Ga₂O₃ buffer layer is reported, yielding a photocurrent of 6 mA cm^?2 at 0 V versus reversible hydrogen electrode (RHE), an onset potential of 0.9 V versus RHE, and 3.5 mA cm^?2 at 0.5 V versus RHE. The quantum efficiency spectrum (incident photon to current efficiency, IPCE) reveals a dramatically improved green/red response and a decreased blue response compared with electrodeposited Cu₂O films. Light intensity dependence and photocurrent transient studies enable the identification of the limitations in the performance. Due to the complementary IPCE curves of thermally oxidized and electrodeposited Cu₂O photocathodes, a dual photocathode is fabricated to maximize the absorption over the entire range of above band gap radiation. Photocurrents of 7 mA cm^?2 at 0 V versus RHE are obtained in the dual photocathodes, with an onset potential of 0.9 V versus RHE and a thermodynamically based energy conversion efficiency of 1.9%.     

Overcoming Charge Collection Limitation at Solid/Liquid Interface by a Controllable Crystal Deficient Overlayer

Bulk and surface charge recombination of photoelectrode are two key processes that significantly hinder solar‐to‐fuel conversion of photoelectrochemical cell (PEC). In this study, the function of a “crystal‐deficient” overlayer is unveiled, which outperforms a traditionally used amorphous or crystalline overlayer in PEC water splitting by exhibiting a high conductivity and large electron diffusion length to enable unlimited electron collection. The optimized ≈2.5 nm thickness of the “crystal‐deficient” shell results in a depletion layer with a width of 3 nm, which overcomes the flat band limitation of the photovoltage and increases the light absorptivity in the wavelength range from 300 to 420 nm. In addition, a 50‐fold increase in the conductivity yields a one‐order‐of‐magnitude increase in the diffusion length of an electron (L_n )(≈20 μm), allowing for unlimited electron collection in the 1.9 μm TiO₂ nanowire array with the “crystal‐deficient” shell. The controllable “crystal‐deficient” overlayer in rutile TiO₂ nanowires photoanode achieves a photocurrent density greater than 2.0 mA cm^?2 at 1.23 V versus reversible hydrogen electrode (RHE), a 1.18% applied bias photon‐to‐current efficiency at 0.49 V versus RHE, a faradaic efficiency greater than 93.5% at 0.6 V versus Pt under air mass 1.5G simulated solar light illumination (100 mW cm^?2).     

Adjusting the Anisotropy of 1D Sb2Se3 Nanostructures for Highly Efficient Photoelectrochemical Water Splitting

Sb₂Se₃ has recently spurred great interest as a promising light‐absorbing material for solar energy conversion. Sb₂Se₃ consists of 1D covalently linked nanoribbons stacked via van der Waals forces and its properties strongly depend on the crystallographic orientation. However, strategies for adjusting the anisotropy of 1D Sb₂Se₃ nanostructures are rarely investigated. Here, a novel approach is presented to fabricate 1D Sb₂Se₃ nanostructure arrays with different aspect ratios on conductive substrates by simply spin‐coating Sb‐Se solutions with different molar ratios of thioglycolic acid and ethanolamine. A relatively small proportion of thioglycolic acid induces the growth of short Sb₂Se₃ nanorod arrays with preferred orientation, leading to fast carrier transport and enhanced photocurrent. After the deposition of TiO₂ and Pt, an appropriately oriented Sb₂Se₃ nanostructure array exhibits a significantly enhanced photoelectrochemical performance; the photocurrent reaches 12.5 mA cm^?2 at 0 V versus reversible hydrogen electrode under air mass 1.5 global illumination.     

Facile and Efficient Atomic Hydrogenation Enabled Black TiO2 with Enhanced Photo‐Electrochemical Activity via a Favorably Low‐Energy‐Barrier Pathway

Black TiO₂ has demonstrated a great potential for a variety of renewable energy technologies. However, its practical application is heavily hindered due to lack of efficient hydrogenation methods and a deeper understanding of hydrogenation mechanisms. Here, a simple and straightforward hot wire annealing (HWA) method is presented to prepare black TiO₂ (H–TiO₂) nanorods with enhanced photo‐electrochemical (PEC) activity by means of atomic hydrogen [H]. Compared to conventional molecular hydrogen approaches, the HWA shows remarkable effectiveness without any detrimental side effects on the device structure, and simultaneously the photocurrent density of H–TiO₂ reaches 2.5 mA cm^?2 (at 1.23 V vs reversible hydrogen electrode (RHE)). Due to the controllable and reproducible [H] flux, the HWA can be developed as a standard hydrogenation method for black TiO₂. Meanwhile, the relationships between the wire temperatures, structural, optical, and photo‐electrochemical properties are systematically investigated to verify the improved PEC activity. Furthermore, the density functional theory (DFT) study provides a comprehensive insight not only into the highly efficient mechanism of the HWA approach but also its favorably low‐energy‐barrier hydrogenation pathway. The findings will have a profound impact on the broad energy applications of H–TiO₂ and contribute to the fundamental understanding of its hydrogenation.     

A Bottom‐Up Approach toward All‐Solution‐Processed High‐Efficiency Cu(In,Ga)S2 Photocathodes for Solar Water Splitting

The development of solution‐processable routes to prepare efficient photoelectrodes for water splitting is highly desirable to reduce manufacturing costs. Recently, sulfide chalcopyrites (Cu(In,Ga)S₂) have attracted attention as photocathodes for hydrogen evolution owing to their outstanding optoelectronic properties and their band gap—wider than their selenide counterparts—which can potentially increase the attainable photovoltage. A straightforward and all‐solution‐processable approach for the fabrication of highly efficient photocathodes based on Cu(In,Ga)S₂ is reported for the first time. It is demonstrated that semiconductor nanocrystals can be successfully employed as building blocks to prepare phase‐pure microcrystalline thin films by incorporating different additives (Sb, Bi, Mg) that promote the coalescence of the nanocrystals during annealing. Importantly, the grain size is directly correlated to improved charge transport for Sb and Bi additives, but it is shown that secondary effects can be detrimental to performance even with large grains (for Mg). For optimized electrodes, the sequential deposition of thin layers of n‐type CdS and TiO₂ by solution‐based methods, and platinum as an electrocatalyst, leads to stable photocurrents saturating at 8.0 mA cm^–2 and onsetting at ≈0.6 V versus RHE under AM 1.5G illumination for CuInS₂ films. Electrodes prepared by our method rival the state‐of‐the‐art performance for these materials.     

Ultrafine Pt Nanoparticle‐Decorated Pyrite‐Type CoS2 Nanosheet Arrays Coated on Carbon Cloth as a Bifunctional Electrode for Overall Water Splitting

To improve the utilization efficiency of precious metals, metal‐supported materials provide a direction for fabricating highly active and stable heterogeneous catalysts. Herein, carbon cloth (CC)‐supported Earth‐abundant CoS₂ nanosheet arrays (CoS₂/CC) are presented as ideal substrates for ultrafine Pt deposition (Pt‐CoS₂/CC) to achieve remarkable performance toward the hydrogen and oxygen evolution reactions (HER/OER) in alkaline solutions. Notably, the Pt‐CoS₂/CC hybrid delivers an overpotential of 24 mV at 10 mA cm^?2 and a mass activity of 3.89 A Pt_mg^?1, which is 4.7 times higher than that of commercial Pt/C, at an overpotential of 130 mV for catalyzing the HER. An alkali‐electrolyzer using Pt‐CoS₂/CC as a bifunctional electrode enables a water‐splitting current density of 10 mA cm^?2 at a low voltage of 1.55 V and can sustain for more than 20 h, which is superior to that of the state‐of‐the‐art Pt/C+RuO₂ catalyst. Further experimental and theoretical simulation studies demonstrate that strong electronic interaction between Pt and CoS₂ synergistically optimize hydrogen adsorption/desorption behaviors and facilitate the in situ generation of OER active species, enhancing the overall water‐splitting performance. This work highlights the regulation of interfacial and electronic synergy in pursuit of highly efficient and durable supported catalysts for hydrogen and oxygen electrocatalytic applications.     

Rational Design of Core@shell Structured CoSx@Cu2MoS4 Hybridized MoS2/N,S‐Codoped Graphene as Advanced Electrocatalyst for Water Splitting and Zn‐Air Battery

A novel hybrid of small core@shell structured CoS_x@Cu₂MoS₄ uniformly hybridizing with a molybdenum dichalcogenide/N,S‐codoped graphene hetero‐network (CoS_x@Cu₂MoS₄‐MoS₂/NSG) is prepared by a facile route. It shows excellent performance toward the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) in alkaline medium. The hybrid exhibits rapid kinetics for ORR with high electron transfer number of ≈3.97 and exciting durability superior to commercial Pt/C. It also demonstrates great potential with remarkable stability for HER and OER, requiring low overpotential of 118.1 and 351.4 mV, respectively, to reach a current density of 10 mA cm^?2. An electrolyzer based on CoS_x@Cu₂MoS₄‐MoS₂/NSG produces low cell voltage of 1.60 V and long‐term stability, surpassing a device of Pt/C + RuO₂/C. In addition, a Zn‐air battery using cathodic CoS_x@Cu₂MoS₄‐MoS₂/NSG catalyst delivers a high cell voltage of ≈1.44 V and a power density of 40 mW cm^?2 at 58 mA cm^?2, better than the state‐of‐the‐art Pt/C catalyst. These achievements are due to the rational combination of highly active core@shell CoS_x@Cu₂MoS₄ with large‐area and high‐porosity MoS₂/NSG to produce unique physicochemical properties with multi‐integrated active centers and synergistic effects. The outperformances of such catalyst suggest an advanced candidate for multielectrocatalysis applications in metal‐air batteries and hydrogen production.     

Ni Strongly Coupled with Mo2C Encapsulated in Nitrogen‐Doped Carbon Nanofibers as Robust Bifunctional Catalyst for Overall Water Splitting

It is urgently required to develop highly efficient and stable bifunctional non‐noble metal electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for water splitting. In this study, a facile electrospinning followed by a post‐carbonization treatment to synthesize nitrogen‐doped carbon nanofibers (NCNFs) integrated with Ni and Mo₂C nanoparticles (Ni/Mo₂C‐NCNFs) as water splitting electrocatalysts is developed. Owing to the strong hydrogen binding energy on Mo₂C and high electrical conductivity of Ni, synergetic effect between Ni and Mo₂C nanoparticles significantly promote both HER and OER activities. The optimized hybrid (Ni/Mo₂C(1:2)‐NCNFs) delivers low overpotentials of 143 mV for HER and 288 mV for OER at a current density of 10 mA cm^?2. An alkaline electrolyzer with Ni/Mo₂C(1:2)‐NCNFs as catalysts for both anode and cathode exhibits a current density of 10 mA cm^?2 at a voltage of 1.64 V, which is only 0.07 V larger than the benchmark of Pt/C‐RuO₂ electrodes. In addition, an outstanding long‐term durability during 100 h testing without obvious degradation is achieved, which is superior to most of the noble‐metal‐free electrocatalysts reported to date. This work provides a simple and effective approach for the preparation of low‐cost and high‐performance bifunctional electrocatalysts for efficient overall water splitting.     

Ultralow Ru Loading Transition Metal Phosphides as High‐Efficient Bifunctional Electrocatalyst for a Solar‐to‐Hydrogen Generation System

Water splitting is a promising technology for sustainable conversion of hydrogen energy. The rational design of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) bifunctional electrocatalysts with superior activity and stability in the same electrolyte is the key to promoting their large‐scale applications. Herein, an ultralow Ru (1.08 wt%) transition metal phosphide on nickel foam (Ru–MnFeP/NF) derived from Prussian blue analogue, that effectively drivies both the OER and the HER in 1 m KOH, is reported. To reach 20 mA cm^?2 for OER and 10 mA cm^?2 for HER, the Ru–MnFeP/NF electrode only requires overpotentials of 191 and 35 mV, respectively. Such high electrocatalytic activity exceeds most transition metal phosphides for the OER and the HER, and even reaches Pt‐like HER electrocatalytic levels. Accordingly, it significantly accelerates full water splitting at 10 mA cm^?2 with 1.470 V, which outperforms that of the integrated RuO₂ and Pt/C couple electrode (1.560 V). In addition, the extremely long operational stability (50 h) and the successful demonstration of a solar‐to‐hydrogen generation system through full water splitting provide more flexibility for large‐scale applications of Ru–MnFeP/NF catalysts.     

Poly(1,4‐di(2‐thienyl))benzene Facilitating Complete Light‐Driven Water Splitting under Visible Light at High pH

The recent discovery that metal‐free polyterthiophene (PTTh) prepared by iodine‐vapor‐assisted polymerization (IVP) can catalyze the hydrogen evolution reaction (HER) when illuminated, and this light‐enhanced electrolysis expresses a non‐Nernstian relation with pH, provides the foundation for further improvement of the photovoltage of the reaction by engineering the band structure of the light‐absorbing polymer. Deviating from an all‐thiophene backbone, using poly(1,4‐di(2‐thienyl))benzene (PDTB) lowers the highest occupied molecular orbital level by ≈0.3 eV compared with polythiophene, and PDTB simultaneously maintains the photoelectrocatalytic properties without an all‐thiophene backbone, resulting in very high conversion rate of 600 mmol(H₂) h^?1 g^?1 at 0 V versus the reversible hydrogen electrode (RHE) at pH 11. PDTB shows the same non‐Nernstian behavior as PTTh with increasing onset potential (versus RHE) at higher pH, and the open circuit potential on PDTB under visible light reaches 1.4 V versus RHE at pH 12. The PDTB photocathode thus produces a photovoltage above the theoretical potential for the complete water‐splitting (1.229 V) and is indeed able to produce hydrogen in a one‐photon‐per‐electron light‐driven water splitting setup with MnO_x as the anode at a rate of 6.4 mmol h^?1 g_PDTB^?1.     

A Cu‐Based Nanoparticulate Film as Super‐Active and Robust Catalyst Surpasses Pt for Electrochemical H2 Production from Neutral and Weak Acidic Aqueous Solutions

Electrocatalysts that are stable and highly active at low overpotential (η) under mild conditions as well as cost‐effective and scalable are eagerly desired for potential use in photo‐ and electro‐driven hydrogen evolution devices. Here the fabrication and characterization of a super‐active and robust Cu‐Cu_xO‐Pt nanoparticulate electrocatalyst is reported, which displays a small Tafel slope (44 mV dec^?1) and a large exchange current density (1.601 mA cm^?2) in neutral buffer solution. The catalytic current density of this catalyst film reaches 500 mA cm^?2 at η = ?390 ± 12 mV and 20 mA cm^?2 at η = ?45 ± 3 mV, which are significantly higher than the values displayed by Pt foil and Pt/C electrodes in neutral buffer solution and even comparable with the activity of Pt electrode in 0.5 m H₂SO₄ solution.     

The “Midas Touch” Transformation of TiO2 Nanowire Arrays during Visible Light Photoelectrochemical Performance by Carbon/Nitrogen Coimplantation

Titanium dioxide is a promising photoanode material for water oxidation, but it is substantially limited by its poor efficiency in the visible light range. Herein, an innovative carbon/nitrogen coimplantation method is utilized to realize the “Midas touch” transformation of TiO₂ nanowire (NW) arrays for photoelectrochemical (PEC) water splitting in visible light. These modified golden–yellow rutile TiO₂ NW arrays (C/N‐TiO₂) exhibit remarkably enhanced absorption in visible light regions and more efficient charge separation and transfer. As a result, the photocurrent density of carbon/nitrogen co‐implanted TiO₂ under visible light (>420 nm) can reach 0.76 mA cm^?2, which far exceeds the value of 3 µA cm^?2 seen for pristine TiO₂ nanowire arrays at 0.8 V versus Ag/AgCl. An incident photon to electron conversion efficiency of ≈14.8% is achieved at 450 nm on C/N‐TiO₂ without any other cocatalysts. The ion implantation doping approach, combined with codoping strategies, is proved to be an effective strategy for enhancing the photoelectrochemical conversion and can enable further improvement of the PEC water‐splitting performance of many other semiconductor photoelectrodes.     

(040)‐Crystal Facet Engineering of BiVO4 Plate Photoanodes for Solar Fuel Production

A (040)‐crystal facet engineered BiVO₄ ((040)‐BVO) photoanode is investigated for solar fuel production. The (040)‐BVO photoanode is favorable for improved charge carrier mobility and high photocatalytic active sites for solar light energy conversion. This crystal facet design of the (040)‐BVO photoanode leads to an increase in the energy conversion efficiency for solar fuel production and an enhancement of the oxygen evolution rate. The photocurrent density of the (040)‐BVO photoanode is determined to be 0.94 mA cm^?2 under AM 1.5 G illumination and produces 42.1% of the absorbed photon‐to‐current conversion efficiency at 1.23 V (vs RHE, reversible hydrogen electrode). The enhanced charge separation efficiency and improved charge injection efficiency driven by (040) facet can produce hydrogen with 0.02 mmol h^?1 at 1.23 V. The correlation between the (040)‐BVO photoanode and the solar fuel production is investigated. The results provide a promising approach for the development of solar fuel production using a BiVO₄ photoanode.     

Earth‐Abundant Iron Diboride (FeB2) Nanoparticles as Highly Active Bifunctional Electrocatalysts for Overall Water Splitting

Developing efficient, durable, and earth‐abundant electrocatalysts for both hydrogen and oxygen evolution reactions is important for realizing large‐scale water splitting. The authors report that FeB₂ nanoparticles, prepared by a facile chemical reduction of Fe²⁺ using LiBH₄ in an organic solvent, are a superb bifunctional electrocatalyst for overall water splitting. The FeB₂ electrode delivers a current density of 10 mA cm^?2 at overpotentials of 61 mV for hydrogen evolution reaction (HER) and 296 mV for oxygen evolution reaction (OER) in alkaline electrolyte with Tafel slopes of 87.5 and 52.4 mV dec^?1, respectively. The electrode can sustain the HER at an overpotential of 100 mV for 24 h and OER for 1000 cyclic voltammetry cycles with negligible degradation. Density function theory calculations demonstrate that the boron‐rich surface possesses appropriate binding energy for chemisorption and desorption of hydrogen‐containing intermediates, thus favoring the HER process. The excellent OER activity of FeB₂ is ascribed to the formation of a FeOOH/FeB₂ heterojunction during water oxidation. An alkaline electrolyzer is constructed using two identical FeB₂‐NF electrodes as both anode and cathode, which can achieve a current density of 10 mA cm^?2 at 1.57 V for overall water splitting with a faradaic efficiency of nearly 100%, rivalling the integrated state‐of‐the‐art Pt/C and RuO₂/C.     

High‐Performance Trifunctional Electrocatalysts Based on FeCo/Co2P Hybrid Nanoparticles for Zinc–Air Battery and Self‐Powered Overall Water Splitting

Currently, it is still a significant challenge to simultaneously boost various reactions by one electrocatalyst with high activity, excellent durability, as well as low cost. Herein, hybrid trifunctional electrocatalysts are explored via a facile one‐pot strategy toward an efficient oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The catalysts are rationally designed to be composed by FeCo nanoparticles encapsuled in graphitic carbon films, Co₂P nanoparticles, and N,P‐codoped carbon nanofiber networks. The FeCo nanoparticles and the synergistic effect from Co₂P and FeCo nanoparticles make the dominant contributions to the ORR, OER, and HER activities, respectively. Their bifunctional activity parameter (?E) for ORR and OER is low to 0.77 V, which is much smaller than those of most nonprecious metal catalysts ever reported, and comparable with state‐of‐the‐art Pt/C and RuO₂ (0.78 V). Accordingly, the as‐assembled Zn–air battery exhibits a high power density of 154 mW cm^?2 with a low charge–discharge voltage gap of 0.83 V (at 10 mA cm^?2) and excellent stability. The as‐constructed overall water‐splitting cell achieves a current density of 10 mA cm^?2 (at 1.68 V), which is comparable to the best reported trifunctional catalysts.     

Superb Alkaline Hydrogen Evolution and Simultaneous Electricity Generation by Pt‐Decorated Ni3N Nanosheets

The development of efficient hydrogen evolution reaction electrocatalysts is critical to the realization of clean hydrogen fuel production, while the sluggish kinetics of the Volmer‐step substantially restricts the catalyst performances in alkali electrolyzers, even for noble metal catalysts such as Pt. Here, a Pt‐decorated Ni₃N nanosheet electrocatalyst is developed to achieve a top performance of hydrogen evolution in alkaline conditions. Possessing a high metallic conductivity and an atomic‐thin semiconducting hydroxide surface, the Ni₃N nanosheets serve as not only an efficient electron pathway without the hindrance of Schottky barriers, but also provide abundant active sites for water dissociation and generation of hydrogen intermediates, which are further adsorbed on the Pt surface to recombine to H₂. The Pt‐decorated Ni₃N nanosheet catalyst exhibits a hydrogen evolution current density of 200 mA cm^?2 at an overpotential of 160 mV versus reversible hydrogen electrode, a Tafel slope of ≈36.5 mV dec^?1, and excellent stability of 82.5% current retention after 24 h of operation. Moreover, a hybrid cell consisting of a Pt‐decorated Ni₃N nanosheet cathode and a Li‐metal anode is assembled to achieve simultaneous hydrogen evolution and electricity generation, exhibiting >60 h long‐term hydrogen evolution reaction stability and an output voltage ranging from 1.3 to 2.2 V.     

Geogrid‐Inspired Nanostructure to Reinforce a CuxZnySnzS Nanowall Electrode for High‐Stability Electrochemical Energy Conversion Devices

Inspired by geogrids commonly applied in construction engineering to reinforce side slopes and retaining walls, the use of a “nano‐geogrid” to reinforce a Cu_x Zn_y Sn_z S (CZTS) nanowall electrode for application in electrochemical reactions is demonstrated. The CZTS nanowall electrode reinforced by the nano‐geogrid (denoted as NWD) shows not only remarkable mechanical and electrochemical stability but also considerable electrochemical performances. The NWD demonstrated as a counter electrode in a dye‐sensitized solar cell shows a power conversion efficiency of 7.44 ± 0.04%, comparable with the device using Pt as electrode, and also significantly improves device stability as compared with that afforded by an electrode comprising a CZTS nanowall without the nano‐geogrid (denoted as NOD). In addition, applying the NWD electrode as a cathode in photo‐electrochemical hydrogen evolution reactions (HERs) yields a photocurrent density of ?10 mA cm^?2 at ?0.162 V (vs RHE) under AM 1.5 illumination. Moreover, when HERs are conducted under extreme conditions, the NWD electrode remains intact, whereas the NOD electrode is completely peeled off after 10 min of reaction. Therefore, the concept of using a mimetic rational nanostructure could pave the way for the possibility of improving the performance and stability of various devices.     

Hydrothermal Synthesis of Monolithic Co3Se4 Nanowire Electrodes for Oxygen Evolution and Overall Water Splitting with High Efficiency and Extraordinary Catalytic Stability

Cobalt selenide has been proposed to be an effective low‐cost electrocatalyst toward the oxygen evolution reaction (OER) due to its well‐suited electronic configuration. However, pure cobalt selenide has by far still exhibited catalytic activity far below what is expected. Herein, this paper for the first time reports the synthesis of new monoclinic Co₃Se₄ thin nanowires on cobalt foam (CF) via a facile one‐pot hydrothermal process using selenourea. When used to catalyze the OER in basic solution, the conditioned monolithic self‐supported Co₃Se₄/CF electrode shows an exceptionally high catalytic current of 397 mA cm^?2 at a low overpotential (η) of 320 mV, a small Tafel slope of 44 mV dec^?1, a turnover frequency of 6.44 × 10^?2 s^?1 at η = 320 mV, and excellent electrocatalytic stability at various current densities. Furthermore, an electrolyzer is assembled using two symmetrical Co₃Se₄/CF electrodes as anode and cathode, which can deliver 10 and 20 mA cm^?2 at low cell voltages of 1.59 and 1.63 V, respectively. More significantly, the electrolyzer can operate at 10 mA cm^?2 over 3500 h and at 100 mA cm^?2 for at least 2000 h without noticeable degradation, showing extraordinary operational stability.