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The performance of electrochromic (EC) devices heavily relies on the properties of both anodic (NiO) and cathodic (WO3) materials, particularly in achieving superior opaqueness. While extensive research has focused on enhancing the cathodic component (WO3), the optimization of the anodic component (NiO) has been relatively neglected, resulting in moderate overall device performance at increased processing costs. Here, we address this concern by optimizing the thickness of the NiO anodic layer to an ultrathin 50 nm using an industrially compatible sputtering technique for superior EC performance. During optimization, the NiO thin film samples were deposited using various oxygen and argon ratios for optimizing their EC properties. Furthermore, the effect of thickness on the electrochromic properties of the optimized NiO was studied. Notably, these films exhibited more than 50% optical modulation at the wavelength of 550 nm with a coloration efficiency of 23.7 cm2 C−1. Structural, morphological, and optical properties were correlated with the electrochromic properties. Electrolytic studies employing different solutions, such as lithium perchlorate in propylene carbonate, aqueous KOH, and LiOH, revealed the superior electrochromic performance of NiO thin films in aqueous LiOH. Furthermore, the dual functionality of the NiO film is demonstrated by showing its charging and discharging capacity in an ITO/aqueous LiOH/NiO/ITO structure with a voltage of >1.8 V in the charged state. Integration of electrochromic capabilities with energy storage highlights the versatility of these films for advanced smart windows. This work may pave the way towards the commercialization of affordable electrochromic smart windows by enhancing the electrochromic contribution from a complementary anodic NiO film of only 50 nm. [ABSTRACT FROM AUTHOR]

Amidst the mounting energy crisis and the pressing need to combat global warming, efficient energy utilization within buildings has emerged as a critical imperative, with buildings currently contributing to 40% of global energy consumption. Electrochromic devices (ECDs), particularly smart windows, have garnered significant attention as a sustainable solution, offering user-controlled light transmission. This manuscript explores the development of a complementary electrochromic device (CECD) utilizing WO3 and NiO electrodes fabricated via pneumatic spray-pyrolysis. By optimizing deposition parameters, exceptional visibility modulation is achieved, surpassing previous reports related to CECD developed using spray pyrolysis. The WO3 cathode exhibits high optical modulations of 66% and 71.5% at 550 nm and 700 nm wavelengths, with rapid response and recovery times. Meanwhile, the NiO anode demonstrates complementary electrochromic properties with optical modulations of 51.5% and 44.5% at the same wavelengths. The resulting CECD, fabricated on a 5 × 5 cm2 scale, showcases optical modulations of 67% and 59% at 550 nm and 700 nm, with remarkable stability over 400 cycles of switching. Furthermore, the device exhibits a high areal capacitance of 2.2 mF cm−2 and coloration efficiencies of 81.59 cm2 C−1 and 102.7 cm2 C−1 at 550 nm and 700 nm, respectively. This study presents a facile and scalable fabrication approach for electrochromic electrodes, offering promising prospects for solution-based methods in electrochromic energy storage applications. [ABSTRACT FROM AUTHOR]

Recently, various single-atom (SA) catalyst-coupled TiO2 nanostructures have been designed for photocatalytic hydrogen evolution. However, TiO2 is a well-established photoanode capable of solar-driven oxygen evolution reaction (OER). Selection and design of suitable oxygen evolution catalysts (OECs) boost the photoelectrochemical (PEC) water oxidation performance of TiO2. Various single-atom catalysts (SACs) are designed mainly for the electrochemical OER, while atomically dispersed SAs on TiO2 photoanodes for the photoelectrochemical (PEC) OER are still to be explored. Here, we demonstrate a rational and effective design of stabilizing Ru SAs dispersed on the CeOx catalyst (Ru:CeOx) coupled with one-dimensional (1D) Sb-doped TiO2 nanorods (Sb–TiO2 NRs) for remarkably enhanced PEC water oxidation activity. The role of Ru SAs in the electronic structure, separation, and transfer of photogenerated charge carriers and water oxidation pathways of the CeOx catalyst coupled photoanode has been investigated. Along with improved visible light absorption, the Ru:CeOx catalyst serves as an efficient hole extraction layer, inducing large interfacial band bending, large photovoltage generation, and shrinkage of the depletion layer, eventually accelerating the photogenerated hole transportation. DFT simulation demonstrates that Ru SA incorporation increases the conductivity of the catalyst, improving photocarrier transfer. Reduced photocarrier recombination, along with enhanced photocarrier transfer and injection rate enhance the photocurrent yield of the photoanode. DFT studies further confirm that Ru SAs significantly reduce the water oxidation overpotential of the neighboring active Ce atom sites, promoting the photoelectrochemical water oxidation activity of the CeOx catalyst. The optimal photoanode delivers a photocurrent density of 1.96 mA cm−2 (at 1.23 V vs. the reversible hydrogen electrode (RHE)), extremely low on-set potential (0.05 VRHE), peak ABPE value of 0.54%, and charge separation efficiency of 61.5% at 1.23 VRHE. This work provides an effective strategy to promote the water oxidation activity of metal oxide-supported SA catalysts to boost the overall performance of photoanodes. [ABSTRACT FROM AUTHOR]

Excessive cost, insufficient optical modulation, and limited functionality are major drawbacks that presently exist in electrochromic smart windows (ECSWs) that are the backbone of zero‐energy buildings. Herein, a solution toward this niche is provided by optimizing various deposition conditions for WO3 sputtering on crackle lithographically fabricated, cost‐effective Al‐mesh overlayed with SnO2. Ultra‐high switching contrast of 90% is accomplished by a decisive choice of parameters i.e., deposition power (5 W cm−2), oxygen flowrate (46 sccm), pressure (2.7 × 10−2 mbar), and film thickness (530 nm) that are imperative for achieving enhanced oxygen deficiency and film porosity. The ECSW displays fast switching with response and recovery time of 11 and 5 s, respectively, which are nearly twice as fast as control ITO‐based device. Additionally, the film holds good cyclic stability with an excellent coloration efficiency of 47 cm2 C−1. As the state‐of‐the‐art, a large‐area smart window (10 × 10 cm2) operable at 2 V is devised engaging WO3 coated Al_SnO2 electrode. The dual‐functionality is demonstrated by employing four series‐connected (5 × 4 cm2, charging time ≈1.5 min) devices to operate a display for 70 min. A device with a quasi‐solid electrolyte is also fabricated, exhibiting improved cyclic stability beyond 2000 cycles. [ABSTRACT FROM AUTHOR]