The development of advanced technology for producing high-purity and lowcost hydrogen is crucial for the upcoming hydrogen economy. One of the most promising technologies to achieve carbon peak and carbon neutrality is hydrogen production through water electrolysis coupled with renewable energy. However, the efficiency of water electrolysis is limited by the catalyst material employed, thereby the pursuit of highly efficient catalysts is of paramount scientific significance. In this review, we focus on the synthesis of electrocatalysts for the hydrogen/oxygen evolution reaction (HER/OER) through various strategies such as hydrogen spillover, heterostructure construction, element doping, monatomic construction, LDH structure modification, high entropy alloy, and other approaches. The article also provides a comprehensive overview of the challenges encountered in enhancing the activity, stability, and durability of transition metal heterogeneous catalysts for both HER and OER. Moreover, the mechanisms of HER and OER are illustrated. The electrocatalysts prepared by these strategies have exhibited promising results in terms of water splitting performance. However, there are still unresolved issues that need to be addressed, such as improving long-term stability and reducing overall cost. Future prospects include exploring new materials and optimizing the preparation methods to further enhance the electrocatalytic activity.
Efficient solar energy utilization technologies are expected to promote the development of a carbon-neutral and renewable energy society. Photovoltaic cells (PVs) have played an important role in the harvest and conversion of solar energy. Due to the intermittent instability of solar energy, however, PVs must be connected with energy storage systems (EESs). Newly developed photoelectrochemical energy storage devices (PESs) are proposed to directly convert solar energy into electrochemical energy. Initial PESs focused on the external and internal integration of PVs and EESs. However, the voltage mismatch between PVs and EESs leads to massive energy loss and unsatisfactory overall performances of PESs. PESs using dual-functional photoactive materials (PAMs), which have simplified device configuration, decreased costs, and external energy loss, have recently emerged for realization of solar-to-electrochemical-energy conversion and storage in a single device. The review summarizes the designing concepts, integrated configurations, and overall performances of different types of PESs, particularly PESs utilizing dual-functional PAMs. Based on the classifications, working principles, basic requirements, and design principles, this review discusses various types of PESs cathodes. Finally, some perspectives are provided for further developing excellent performances of PESs.
Aluminum metal batteries are considered to be promising secondary batteries due to their high theoretical specific capacity. However, metallic aluminum suffers from corrosion, pulverization, and crushing problems in nonaqueous electrolytes. Constructing a solid-electrolyte interphase layer on the anode electrode has been confirmed to be the key to improving the cycling performance of rechargeable batteries. Herein, we demonstrate an Al metal anode with a physical protective layer achieved by a simple blade coating method. This modified Al metal anode demonstrates ultra-low voltage hysteresis (∼25 mV at 0.1 mA cm−2 and ∼30 mV at 1mA cm−2), and superior stability (630 h at 0.1 mA cm−2 and 580 h at 1 mA cm−2). When coupling this anode with flake graphite cathode, the assembled full cells exhibit superior cycling stability (92 mAh g−1 maintained after 740 cycles at 0.1 A g−1). The current work presents a promising approach to stabilize Al metal anodes for next-generation rechargeable aluminum batteries.
The corrosion of mild steel in HCl solution remains a critical issue in various industrial applications. In the quest for effective corrosion inhibitors, 4-(2-Hydroxy-3-Methoxybenzylideneamino) antipyrine (HMBA) has emerged as a promising candidate. This study investigates the inhibitory properties of HMBA on mild steel corrosion in HCl solution through weight loss measurements, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) techniques. The experiments spanned over various time periods, including 1, 5, 10, 24, and 48 h. The results reveal that HMBA exhibits exceptional inhibition efficiency (IE), with an impressive 94.7% inhibition rate. This outstanding performance underscores its potential as a corrosion inhibitor for mild steel in aggressive HCl environments. To elucidate the adsorption behavior of HMBA on the mild steel surface, Langmuir isotherm modeling was employed, demonstrating a strong correlation between the experimental data and the Langmuir adsorption isotherm model. Furthermore, the study employs density functional theory (DFT) to gain insight into the mechanism of HMBA inhibition. DFT calculations suggest that both physisorption and chemisorption mechanisms are involved in the interaction between HMBA and the mild steel surface. The calculated Gibbs free energy of adsorption
As an intermediary between chemical and electric energy, rechargeable batteries with high conversion efficiency are indispensable to empower electric vehicles and stationary energy storage systems. Self-discharge with adverse effects on energy output and lifespan is a long-existing challenge and intensive endeavors have been devoted to alleviating it. Previous reports mainly focused on examining key factors influencing the rate of self-discharge, however, its origination has rarely been revealed from the viewpoint of fundamental electrochemistry. The Evans Diagram, which is a corrosion polarization diagram based on kinetics (corrosion current density) and thermodynamics (potential), is an informative method for analyzing the corrosion process of metals. In this perspective, after an introduction to electrochemical fundamentals, as well as the identical origination of battery self-discharging and metal corrosion, we first transferred the concept of the Evans Diagram to illustrate the origination and evolution of self-discharge in rechargeable batteries. The corresponding Evans Diagram has been proposed for different key factors, which were eventually used as guidance to exploit thermodynamical and kinetical solutions to alleviate the parasitic reactions induced by self-discharge. This contribution is believed to provide new insights towards understanding and regulating self-discharge problems, and promote the establishment of feasible protocols for battery storage in practice.
Over the past decades, there has been a growing interest in rechargeable aqueous Zn-ion batteries (AZIBs) as a viable substitute for lithium-ion batteries. This is primarily due to their low cost, lower redox potential, and high safety. Nevertheless, the progress of Zn metal anodes has been impeded by various challenges, including the growth of dendrites, corrosion, and hydrogen evolution reaction during repeated cycles that result in low Coulombic efficiency and a short lifetime. Therefore, we represent recent advances in Zn metal anode protection for constructing high-performance AZIBs. Besides, we show in-depth analyses and supposed hypotheses on the working mechanism of these issues associated with mildly acidic aqueous electrolytes. Meanwhile, design principles and feasible strategies are proposed to suppress dendrites’ formation of Zn batteries, including electrode design, electrolyte modification, and interface regulation, which are suitable for restraining corrosion and hydrogen evolution reaction. Finally, the current challenges and future trends are raised to pave the way for the commercialization of AZIBs. These design principles and potential strategies are applicable in other metal-ion batteries, such as Li and K metal batteries.
The conversion of CO2 into chemical fuels, which can be stored and utilized through photocatalysis, represents an effective, environmentally friendly, and sustainable means to address both environmental concerns and energy shortages. CO2, as a stable oxidation product, poses challenges for reduction through light energy alone, necessitating the use of catalysts. Thus, a crucial aspect of CO2 photocatalytic reduction technology lies in the development of effective photocatalysts. Based on the basic principle of PCRR (photocatalytic CO2 reduction reaction), the review provides a detailed introduction to the core issues in PCRR process, including the relationship between band gap and catalyst reduction performance, effective utilization of photogenerated carriers, product selectivity, and methods for product analysis. Then, the recent research progresses of various photocatalysts are reviewed in the form of research examples combined with the above basic principles. Finally, this review summarizes and provides insights into the effective techniques for enhancing the photocatalytic activity of CO2, while also offering future prospects in this field.