A Low-Cost and High-Efficiency Integrated Device toward Solar-Driven Water Splitting

Rapid Formation of Epitaxial Oxygen Evolution Reaction Catalysts on Dendrites with High Catalytic Activity and Stability

Oxygen evolution reaction is an essential but kinetically sluggish step in many energy storage and conversion processes and therefore is in pursuit of highly efficient and stable catalysts. Although nanosized transition-metal-based oxides/hydroxides exhibit high catalytic activity toward the oxygen evolution reaction (OER), many of them suffer from low stability at an anode current density in industrial scale. Herein, by combining a rapid epitaxial formation method with dynamic bubble-templated electrodeposition, we successfully developed single crystalline NiFeCu oxide catalysts with a hierarchical porous structure. It was found that the structure can facilitate fast electron transportation for the catalysts and retard the diffusion of the O atoms to the inner metallic current collector. The hierarchical pores inherited from the hydrogen bubble templates built ideal channels for the massive and rapid release of oxygen bubbles. As a consequence, the NiFeCu oxides catalyzed the OER more efficiently and steadily than the commercial RuO2 catalyst at an anode current density in industrial scale (300 mA/cm2). This work, by resolving the durability concerns for nanosized oxides, offers a series of highly efficient and stable catalysts for OER and a structure building strategy to boost the catalytic activity and stability for nonconductive catalysts.

Efficient Solar-Driven Water Splitting Enabled by Perovskite Photovoltaics and a Halogen-Modulated Metal-Organic Framework Electrocatalyst

Solar-driven water splitting powered by photovoltaics enables efficient storage of solar energy in the form of hydrogen fuel. In this work, we demonstrate efficient solar-to-hydrogen conversion using perovskite (PVK) tandem photovoltaics and a halogen-modulated metal-organic framework (MOF) electrocatalyst. By substituting tetrafluoroterephthalate (TFBDC) for terephthalic (BDC) ligands in a nickel-based MOF, we achieve a 152 mV improvement in oxygen evolution reaction (OER) overpotential at 10 mA·cm2. Through X-ray photoelectron spectroscopy (XPS), X-ray adsorption structure (XAS) analysis, theoretical simulation, and electrochemical results, we demonstrated that the introduction of fluorine atoms enhanced the intrinsic activity of Ni sites as well as the transfer property and accessibility of the MOF. Using this electrocatalyst in a bias-free photovoltaic electrochemical (PV-EC) system with a PVK/organic tandem solar cell, we achieve 6.75% solar-to-hydrogen efficiency (ηSTH). We also paired the electrocatalyst with a PVK photovoltaic module to drive water splitting at 206.7 mA with ηSTH of 10.17%.

Perovskite-Solar-Cell-Powered Integrated Fuel Conversion and Energy-Storage Devices

Metal halide hybrid perovskite solar cells (PSCs) have received considerable attention over the past decade owing to their potential for low-cost, solution-processable, earth-abundant, and high-performance superiority, increasing power conversion efficiencies of up to 25.7%. Solar energy conversion into electricity is highly efficient and sustainable, but direct utilization, storage, and poor energy diversity are difficult to achieve, resulting in a potential waste of resources. Considering its convenience and feasibility, converting solar energy into chemical fuels is regarded as a promising pathway for boosting energy diversity and expanding its utilization. In addition, the energy conversion-storage integrated system can efficiently sequentially capture, convert, and store energy in electrochemical energy storage devices. However, a comprehensive overview focusing on PSC-self-driven integrated devices with a discussion of their development and limitations remains lacking. Here, focus is on the development of representative configurations of emerging PSC-based photo-electrochemical devices including self-charging power packs, unassisted solar water splitting/CO2 reduction. The advanced progresses in this field, including configuration design, key parameters, working principles, integration strategies, electrode materials, and their performance evaluations are also summarized. Finally, scientific challenges and future perspectives for ongoing research in this field are presented.

Integrated halide perovskite photoelectrochemical cells with solar-driven water-splitting efficiency of 20.8

Achieving high solar-to-hydrogen (STH) efficiency concomitant with long-term durability using low-cost, scalable photo-absorbers is a long-standing challenge. Here we report the design and fabrication of a conductive adhesive-barrier (CAB) that translates >99% of photoelectric power to chemical reactions. The CAB enables halide perovskite-based photoelectrochemical cells with two different architectures that exhibit record STH efficiencies. The first, a co-planar photocathode-photoanode architecture, achieved an STH efficiency of 13.4% and 16.3 h to t₆₀, solely limited by the hygroscopic hole transport layer in the n-i-p device. The second was formed using a monolithic stacked silicon-perovskite tandem, with a peak STH efficiency of 20.8% and 102 h of continuous operation before t₆₀ under AM 1.5G illumination. These advances will lead to efficient, durable, and low-cost solar-driven water-splitting technology with multifunctional barriers.

Simultaneous Photoluminescence and Photothermal Investigation of Individual CH3NH3PbBr3 Microcrystals

The photoluminescence (PL) of CH₃NH₃PbBr₃ (MAPbBr₃), from thin films to nanoparticles, has been widely studied, providing information about charge carrier dynamics. However, the other energy dissipative channel, nonradiative relaxation, has not been thoroughly investigated due to a lack of proper technology. In this work, we simultaneously investigated the PL and photothermal (PT) properties of single MAPbBr₃ microcrystals (MCs) by a home-built PL and PT microscope. In addition to the direct observation of the heterogeneity of the PL and PT images and kinetics of different MCs, we demonstrated the variation in the absorption of single MAPbBr₃ MCs, which was believed to be constant. We also proved that more absorbed energy dissipated from the nonradiative channel at higher heating power. These results show that PL and PT microscopy is an effective and convenient method to investigate the charge carrier behaviors of optoelectronic materials at the single particle level for a deep understanding of their photophysical processes.

Interface Engineering on Amorphous/Crystalline Hydroxides/Sulfides Heterostructure Nanoarrays for Enhanced Solar Water Splitting

Developing highly efficient and stable noble-metal-free electrocatalysts for water splitting is critical for producing clean and sustainable energy. Here, we design a hierarchical transition metal hydroxide/sulfide (NiFe(OH)_x-Ni₃S₂/NF) electrode with dual heterointerface coexistence using a cation exchange-induced surface reconfiguration strategy. The electrode exhibits superior electrocatalytic activities, achieving low overpotentials of 55 mV for hydrogen evolution and 182 mV for oxygen evolution at 10 mA cm^-2. Furthermore, the assembled two-electrode system requires voltages as low as 1.55 and 1.62 V to deliver industrially relevant current densities of 500 and 1000 mA cm^-2, respectively, with excellent durability for over 200 h, which is comparable to commercial electrolysis. Theoretical calculations reveal that the hierarchical heterostructure increases the electronic delocalization of the Fe and Ni catalytic centers, lowering the energy barrier of the rate-limiting step and promoting O₂ desorption. Finally, by implementing the catalysts in a solar-driven water electrolysis system, we demonstrate a record and durable solar-to-hydrogen (STH) conversion efficiency of up to 20.05%. This work provides a promising strategy for developing low-cost and high-efficiency bifunctional catalysts for a large-scale solar-to-hydrogen generation.

Super-Hydrophilic Leaflike Sn4P3 on the Porous Seamless Graphene-Carbon Nanotube Heterostructure as an Efficient Electrocatalyst for Solar-Driven Overall Water Splitting

Water splitting using renewable energy resources is an economic and green approach that is immensely enviable for the production of high-purity hydrogen fuel to resolve the currently alarming energy and environmental crisis. One of the effective routes to produce green fuel with the help of an integrated solar system is to develop a cost-effective, robust, and bifunctional electrocatalyst by complete water splitting. Herein, we report a superhydrophilic layered leaflike Sn₄P₃ on a graphene-carbon nanotube matrix which shows outstanding electrochemical performance in terms of low overpotential (hydrogen evolution reaction (HER), 62 mV@10 mA/cm², and oxygen evolution reaction (OER), 169 mV@20 mA/cm²). The outstanding stability of HER at least for 15 days at a high applied current density of 400 mA/cm² with a minimum loss of potential (1%) in acid medium infers its potential compatibility toward the industrial sector. Theoretical calculations indicate that the decoration of Sn₄P₃ on carbon nanotubes modulates the electronic structure by creating a higher density of state near Fermi energy. The catalyst also reveals an admirable overall water splitting performance by generating a low cell voltage of 1.482 V@10 mA/cm² with a stability of at least 65 h without obvious degradation of potential in 1 M KOH. It exhibited unassisted solar energy-driven water splitting when coupled with a silicon solar cell by extracting a high stable photocurrent density of 8.89 mA/cm² at least for 90 h with 100% retention that demonstrates a high solar-to-hydrogen conversion efficiency of ∼10.82%. The catalyst unveils a footprint for pure renewable fuel production toward carbon-free future green energy innovation.

Solar-to-Chemical Fuel Conversion via Metal Halide Perovskite Solar-Driven Electrocatalysis

Sunlight is an abundant and clean energy source, the harvesting of which could make a significant contribution to society's increasing energy demands. Metal halide perovskites (MHP) have recently received attention for solar fuel generation through photocatalysis and solar-driven electrocatalysis. However, MHP photocatalysis is limited by low solar energy conversion efficiency, poor stability, and impractical reaction conditions. Compared to photocatalysis, MHP solar-driven electrocatalysis not only exhibits higher solar conversion efficiency but also is more stable when operating under practical reaction conditions. In this Perspective, we outline three leading types of MHP solar-driven electrocatalysis device technologies now in the research spotlight, namely, (1) photovoltaic-electrochemical (PV-EC), (2) photovoltaic-photoelectrochemical (PV-PEC), and (3) photoelectrochemical (PEC) approaches for solar-to-fuel reactions, including water-splitting and the CO₂ reduction reaction. In addition, we compare each technology to show their relative technical advantages and limitations and highlight promising research directions for the rapidly emerging scientific field of MHP-based solar-driven electrocatalysis.

Noble-Metal-Free Multicomponent Nanointegration for Sustainable Energy Conversion

Global energy and environmental crises are among the most pressing challenges facing humankind. To overcome these challenges, recent years have seen an upsurge of interest in the development and production of renewable chemical fuels as alternatives to the nonrenewable and high-polluting fossil fuels. Photocatalysis, photoelectrocatalysis, and electrocatalysis provide promising avenues for sustainable energy conversion. Single- and dual-component catalytic systems based on nanomaterials have been intensively studied for decades, but their intrinsic weaknesses hamper their practical applications. Multicomponent nanomaterial-based systems, consisting of three or more components with at least one component in the nanoscale, have recently emerged. The multiple components are integrated together to create synergistic effects and hence overcome the limitation for outperformance. Such higher-efficiency systems based on nanomaterials will potentially bring an additional benefit in balance-of-system costs if they exclude the use of noble metals, considering the expense and sustainability. It is therefore timely to review the research in this field, providing guidance in the development of noble-metal-free multicomponent nanointegration for sustainable energy conversion. In this work, we first recall the fundamentals of catalysis by nanomaterials, multicomponent nanointegration, and reactor configuration for water splitting, CO₂ reduction, and N₂ reduction. We then systematically review and discuss recent advances in multicomponent-based photocatalytic, photoelectrochemical, and electrochemical systems based on nanomaterials. On the basis of these systems, we further laterally evaluate different multicomponent integration strategies and highlight their impacts on catalytic activity, performance stability, and product selectivity. Finally, we provide conclusions and future prospects for multicomponent nanointegration. This work offers comprehensive insights into the development of cost-competitive multicomponent nanomaterial-based systems for sustainable energy-conversion technologies and assists researchers working toward addressing the global challenges in energy and the environment.

NiMoV and NiO-based catalysts for efficient solar-driven water splitting using thermally integrated photovoltaics in a scalable approach

In this work, a trimetallic NiMoV catalyst is developed for the hydrogen evolution reaction and characterized with respect to structure, valence, and elemental distribution. The overpotential to drive a 10 mA cm⁻² current density is lowered from 94 to 78 mV versus reversible hydrogen electrode by introducing V into NiMo. A scalable stand-alone system for solar-driven water splitting was examined for a laboratory-scale device with 1.6 cm² photovoltaic (PV) module area to an up-scaled device with 100 cm² area. The NiMoV cathodic catalyst is combined with a NiO anode in alkaline electrolyzer unit thermally connected to synthesized (Ag,Cu) (In,Ga)Se₂ ((A)CIGS) PV modules. Performance of 3- and 4-cell interconnected PV modules, electrolyzer, and hydrogen production of the PV electrolyzer are examined between 25°C and 50°C. The PV-electrolysis device having a 4-cell (A)CIGS under 100 mW cm⁻² illumination and NiMoV-NiO electrolyzer shows 9.1% maximum and 8.5% averaged efficiency for 100 h operation.

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A new catalyst NiMoV is reported for the hydrogen evolution reaction

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A scalable thermally integrated PV-electrolyzer is designed for solar water splitting

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Interconnected PV-electrolyzer modules provide STH efficiency between 8 and 11%

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An upscaled CIGS-NiMoV-NiO device provides 8.5% STH for 100 h operation

The design of an inner-motile waste-energy-driven piezoelectric catalytic system

A kind of waste-energy-driven catalytic system was explored for the first time using magnetically actuated artificial cilia.