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High entropy materials (HEM) have been attracting much attention as emerging catalysts for electrochemical water splitting. HEM catalysts have unique properties such as an interesting cocktail effect, broad design space, customizable electronic structure, and excellent entropy stabilization effect compared with single-digit catalysts. This paper provides a comprehensive overview of the use of HEM as a catalyst for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and water splitting. HEM design strategies including phase structure modulation, defect engineering, electrode configuration engineering, and computational aids are discussed to develop HEM catalysts with high performance and stability. In particular, the importance of density functional theory, high-throughput screening techniques, and machine learning for the discovery and design of HEM catalysts is emphasized. Finally, the challenges and imminent difficulties are prospected, and the corresponding strategies to deal with these challenges are put forward to promote the development of HEM catalysts in the field of electrochemical water splitting. [ABSTRACT FROM AUTHOR]

The development of efficient non-noble metal electrocatalysts for the oxygen evolution reaction (OER) under acidic conditions remains a critical challenge. Herein, we report a N-doped carbonaceous component-engineered Co3O4 (NCEC) catalyst synthesized via the sol-gel method. Dopamine hydrochloride (DA)-derived nitrogen-doped carbonaceous components were found to boost the OER performance of Co3O4. The optimized catalyst can reach an overpotential as low as 330 mV in 1 M H2SO4 at a current density of 10 mA cm-2 and maintains a good long-term stability of 60 hours. In particular, we found that the thermodynamic overpotential was inversely proportional to the content of oxidized N and pyridinic N, whereas it was directly proportional to the pyrrolic-N content. Our experiments and density functional theory (DFT) calculations confirm that the optimized catalyst exhibits enhanced charge transfer and the oxidized N species on Co3O4 is responsible for the high catalytic activity. Our study suggests that the performance of NCEC in acidic media can be further optimized by enhancing the content of oxidized N species. [ABSTRACT FROM AUTHOR]

The design of low-cost and high-performance bifunctional catalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is of great significance for overall water splitting. Herein, RuNi single atom alloy (SAA) decorated on reduced graphene oxide (RuNi@rGO) was synthesized by a facile strategy for use as a bifunctional HER/OER catalyst. The as-obtained RuNi@rGO catalyst exhibits outstanding electrocatalytic activities with an ultralow overpotential for the HER (15 mV) and the OER (240 mV) at a current density of 10 mA cm−2. Density functional theory (DFT) calculations demonstrate that the introduction of Ru single atoms can evidently change the electron distribution and coordination environment around Ni, and reduce the intermediate's adsorption free energy of RuNi@rGO, thus facilitating the HER/OER catalytic rate. Moreover, when used as the cathode and anode of a two-electrode system, the RuNi@rGO-based water splitting device exhibits a low potential of 1.52 V at a current density of 10 mA cm−2, as well as a high faradaic efficiency almost up to 100%, making RuNi@rGO bifunctional electrocatalysts attractive for energy storage and conversion. [ABSTRACT FROM AUTHOR]

CP@NC-CoFe 2 O 4 /C as catalysts for OER: we covered a polyaniline nanowire array on carbon paper by a electrochemical polymerization method, directly grown MOF-74-Co/Fe on its surface and pyrolyzed to form the CoFe 2 O 4 /C supported on nitrogen-doped carbon nanoarray meterial, which is prepared a highly active and stable OER catalyst. High specific surface area, high utilization of the catalyst, enhanced electron transport characteristics and retention characteristics of the original carbon paper characteristics ensure excellent OER activity. Our results show great promise for developing OER catalysts as precious metal substitutes for PANI and MOFs complexes through a low-cost, scalable method. [Display omitted] • Polyaniline nanowire array was covered on carbon paper, directly grown MOF-74-Co/Fe on its surface. • The presence of PANI nanowire arrays also retains the original properties of carbon paper. • The unique 3D nano-array structure enhance the OER catalytic efficiency. • DFT reveals the main surface adsorbent is OH*, and surface Co atoms are the main active sites. Here, we covered a polyaniline nanowire array (denoted as PANI) on carbon paper (denoted as CP) by a electrochemical polymerization method, directly grown MOF-74-Co/Fe on its surface and pyrolyzed to form the CoFe 2 O 4 /C supported on nitrogen-doped carbon nanoarray materials (denoted as NC-CoFe 2 O 4 /C@CP), which is prepared a highly active and stable OER catalyst. PANI can not only be used as a "binder", grow MOF on its surface and cover the carbon paper, but also improve the conductivity and stability of the material by forming nitrogen-doped carbon after pyrolysis. And its unique 3D nano-array structure not only greatly increases the surface area, but also provides more attachment sites for CoFe 2 O 4 , thereby accelerating electron transport and improving OER performance. High specific surface area, high utilization of the catalyst, enhanced electron transport characteristics and retention characteristics of the original carbon paper characteristics ensure excellent OER activity. The final sample exhibits outstanding activity for OER in alkaline solution, accompanied by a low onset potential about 1.52 V (vs reversible hydrogen electrode), and the small Tafel slope of 70 mV dec−1. In particular, after 21600s, the current drop is negligible, which is means that the NC-CoFe 2 O 4 /C@CP catalyst has the high stability. Density Functional Theory (DFT) calculation reveals the main surface adsorbent of CoFe 2 O 4 is OH*, and the surface Co atoms are the main active sites. [ABSTRACT FROM AUTHOR]

Electrocatalytic water splitting, which is driven by renewable energy input to produce oxygen, has been widely regarded as a promising strategy in the future energy portfolio. The two-dimensional structure based on CoOOH nanosheets is easy to handle in the preparation process, low in cost, and has a small overpotential during water decomposition. Therefore, CoOOH two-dimensional materials have been widely used as electrocatalysts for the oxygen evolution reaction (OER). In this paper, we summarize the application of two-dimensional CoOOH nanosheets in the field of oxygen production from electrocatalytic water splitting. First, the different preparation methods of two-dimensional CoOOH nanosheets are briefly introduced. The structure–activity relationship of the two-dimensional CoOOH catalyst was analyzed from different viewpoints, such as doping, defects, etc. Finally, different catalytic mechanisms of CoOOH-based catalysts are discussed, and studies at the density functional theory (DFT) level are also provided to support the above mechanisms. To improve the readability of this review, a concise overview at the end of each section is given to illustrate some of the characteristics and trends of the studies in the corresponding part. The opportunities and challenges of two-dimensional CoOOH as an electrocatalyst in the future are summarized in the Conclusion section. This work will provide new insights and perspectives to the readers to understand the role of CoOOH nanosheets in the OER process. [ABSTRACT FROM AUTHOR]

In this paper, the bifunctional Ir cluster-decorated carbon Composite (Ir/C-1) electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are synthesized through simple in-situ growth of bimetallic Zn-Ir-MOF, followed by Zn reduction and evaporation for creating pore structure and uniform particle distribution. The prepared catalyst of Ir/C-1 with Ir cluster (d = 3 ± 0.1 nm) highly dispersed and closely attached to pore carbon through Ir-O-C bonds shows both excellent OER and HER performance. At a current density of 10 mA cm-2, the catalyst shows overpotentials of only 50.4 mV for HER and 359 mV for OER in 0.5 M H2SO4, respectively, which are better than commercial Ir/C and Pt/C catalysts. Density functional theory (DFT) calculations further revealed that the exposure of Ir (110) in Ir/C-1 can facilitate the thermodynamic process of HER and OER. This paper also gives a detailed discussion about the enhancement mechanism. To validate the catalyst, a single electrolysis cell is assembled using the prepared Ir/C-1 catalyst as both the anode and cathode catalysts. The result shows that the cell only needs a cell voltage of 1.653 V to obtain a current density of 10 mA cm-2, which is better than commercial Ir/C and Pt/C catalysts. [ABSTRACT FROM AUTHOR]

Generation of molecular hydrogen by electrochemical water splitting is a promising approach, and its efficiency strictly depends on the electrocatalyst used. Therefore, it is an ongoing challenge to design materials having improved the electrocatalytic behaviour towards hydrogen evolution reaction. Here, using Co-MOF [Co4(BTC)3(BIm)6] as starting precursor, graphitic carbon encapsulated CoSe2 nanorods have been prepared through a single step selenization method. The carbon network in the CoSe2/C hybrid nanostructure forms channels, facilitating the accessibility of the electrolyte ions and maximizing the utilization of catalytic active centers. This makes the hybrid to show higher electrochemical accessible surface area, lower charge transfer resistance, and improved catalytic durability towards the electrocatalytic hydrogen evolution reaction with respect to the non-noble metal (graphite rod) counter electrode. Specifically, it needs only 253 mV of overpotential to reach the benchmarked current density (10 mA cm−2) with a lower Tafel slope. Further, the experimental findings have been supported by the theoretical analysis of the structure and electronic properties of CoSe2 and CoSe2/C hybrid by density functional theory (DFT) simulations. The interaction between CoSe2 and C is due to charge transfer from Co 3d orbital and Se 4p orbital of CoSe2 to the 2p orbital of carbon. Also, populated electronic states near Fermi level for C doped CoSe2 may infer towards increased conductivity of the material. Computed overpotentials for HER activities show a qualitative order of CoSe2/C < CoSe2, matching nicely with the experimental data. The synergic effect of increased conductivity, improved surface area, and superior electrocatalytic activity due to C doping is responsible for the superior HER catalytic performance. [ABSTRACT FROM AUTHOR]

The absence of efficient and durable catalysts for oxygen evolution reaction (OER) is the main obstacle to hydrogen production through water splitting in an acidic electrolyte. Here, we report a controllable synthesis method of surface IrO x with changing Au/Ir compositions by constructing a range of sub-10-nm-sized core-shell nanocatalysts composed of an Au core and Au x Ir1−x alloy shell. In particular, Au@Au0.43Ir0.57 exhibits 4.5 times higher intrinsic OER activity than that of the commercial Ir/C. Synchrotron X-ray-based spectroscopies, electron microscopy and density functional theory calculations revealed a balanced binding of reaction intermediates with enhanced activity. The water-splitting cell using a load of 0.02 mgIr/cm2 of Au@Au0.43Ir0.57 as both anode and cathode can reach 10 mA/cm2 at 1.52 V and maintain activity for at least 194 h, which is better than the cell using the commercial couple Ir/C‖Pt/C (1.63 V, 0.2 h). [ABSTRACT FROM AUTHOR]

The design and synthesis of hybrid core–shell catalysts is of great significance for obtaining an excellent performance of hydrogen evolution reaction (HER). However, it remains a challenge to explore the exact active sites and research the catalytic mechanism for HER. Here, a series of Ni3S2@MOOH/NF (M = Fe, Ni, Cu, Mn and Co) hybrid structures is firstly in-site grown on Ni foam by the typical hydrothermal and electrodeposition methods. The Ni3S2@NiOOH/NF catalyst with a core–shell structure exhibits a relatively low overpotential of 79 mV for HER at a current density of 10 mA cm−2, which is one of the best catalytic activities reported so far. Moreover, it also shows good stability in the long-term durability test. Various spectral analysis and density functional theory calculations demonstrate that NiOOH is favorable for the adsorption of water molecules, and the S atom at the interface between Ni3S2 and NiOOH is favorable for the adsorption of H intermediates, which strongly accelerates the HER process in alkaline solution. This work provides a general strategy for the synthesis of electrocatalytic materials, which can be used for efficient electrocatalytic water splitting reactions. [ABSTRACT FROM AUTHOR]

Antibiotic pollution in aqueous solutions seriously endangers the natural environment and public health. In this work, Mo-doped transition metal FeCo--Se metal aerogels (MAs) were investigated as bifunctional catalysts for the removal of sulfamethazine (SMT) in solution. The optimal Mo0.3Fe1Co3--Se catalyst can remove 97.7% of SMT within 60 min (SMT content: 10 mg/L, current intensity: 10 mA/cm²). The unique porous cross-linked structure of aerogel confered the catalyst sufficient active sites and efficient mass transfer channels. For the anode, Mo0.3Fe1Co3--Se MAs exhibits superior oxygen evolution reaction (OER) property, with an overpotential of only 235 mV (10 mA/cm²). Compared with Fe1Co3 MAs or Mo0.3Fe1Co3 MAs, density functional theory (DFT) demonstrated that the better catalytic capacity of Mo0.3Fe1Co3--Se MAs is attributed to the doping of Mo species and selenization lowers the energy barrier for the *OOH to O2 step in the OER process. Excellent OER performance ensures the self-oxygenation in this system, avoiding the addition of air or oxygen in the traditional electro-Fenton process. For the cathode, Mo doping can lead to the lattice contraction and metallic character of CoSe2, which is beneficial to accelerate electron transfer. The adjacent Co active sites effectively adsorb *OOH and inhibit the breakage of the O--O bond. Rotating ring disk electrode (RRDE) test indicated that Mo0.3Fe1Co3--Se MAs has an excellent 2e- ORR activity with H2O2 selectivity up to 88%, and the generated H2O2 is activated by the adjacent Fe site through heterogeneous Fenton process to generate ·OH. [ABSTRACT FROM AUTHOR]

Binary single‐atom catalysts (BSACs) have demonstrated fascinating activities compared to single atom catalysts (SACs) for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Notably, Fe SACs is one of the most promising ORR electrocatalysts, and further revealing the synergistic effects between Fe and other 3d transition metals (M) for FeM BSACs are very important to enhance bifunctional performance. Herein, density functional theory (DFT) calculations are first adapted to demonstrate the role of various transition metals on the bifunctional activity of Fe sites, and a notable volcano relationship is established through the generally accepted adsorption free energy that ΔG*OH for ORR, and ΔG*O−ΔG*OH for OER, respectively. Further, ten of the atomically dispersed FeM anchored on nitrogen‐carbon support (FeM‐NC) are successfully synthesized with typical atomic dispersion by a facile movable type printing method. The experimental data confirms the bifunctional activity diversity of FeM‐NC between the early‐ and late‐ transition metals, agrees very well with the DFT results. More importantly, the optimal FeCu‐NC shows the expected performance with high ORR and OER activity, thereby, the assembled rechargeable zinc–air battery delivers a high power density of 231 mW cm−2, and an impressive stability that can be stably operated over 300 h. [ABSTRACT FROM AUTHOR]

Surging interests exist in double‐atom catalysts (DACs), which not only inherit the advantages of single‐atom catalysts (SACs) (e.g., ultimate atomic utilization, high activity, and selectivity) but also overcome the drawbacks of SACs (e.g., low loading and isolated active site). The design of DACs, however, remains cost‐prohibitive for both experimental and computational studies, due to their huge design space. Herein, by means of density functional theory (DFT) and topological information‐based machine‐learning (ML) algorithms, we present a data‐driven high‐throughput design principle to evaluate the stability and activity of 16 767 DACs for oxygen evolution (OER) and oxygen reduction (ORR) reactions. The rational design reveals 511 types of DACs with OER activity superior to IrO2 (110), 855 types of DACs with ORR activity superior to Pt (111), and 248 bifunctional DACs with high catalytic performance for both OER and ORR. An intrinsic descriptor is revealed to correlate the catalytic activity of a DAC with the electronic structures of the DAC and its bonding carbon surface structure. This data‐driven high‐throughput approach not only yields remarkable prediction precision (>0.926 R‐squared) but also enables a notable 144 000‐fold reduction of screening time compared with pure DFT calculations, holding promise to drastically accelerate the design of high‐performance DACs. [ABSTRACT FROM AUTHOR]

Developing bifunctional electrocatalysts is the primary challenge to improve the reaction efficiency of zinc‐air batteries. Lattice‐strain engineering constructs high‐efficiency oxygen redox catalysts by tuning the physicochemical properties of nanomaterials. However, the randomness and complexity of lattice mismatch make it difficult to effectively identify the structure–activity relationship between the strain and catalyst. Herein, a strategy of Ru triggered partial coordination environment mutation of ZnIn2S4 (R0.1ZIS) to regulate the d‐band center of catalytic sites is provided, which dramatically activates intrinsic activity and accelerates electron transfer. Density functional theory calculations and system characterizations reveal that local lattice strain causes anti‐bonding orbital to occupy more electrons and narrower bandwidth, reduce the migration energy barrier of *OH deprotonation and optimize the adsorption/desorption process of oxygen‐containing intermediates, thus demonstrating extraordinary catalytic performance in oxygen reduction reaction and oxygen evolution reaction. Expectedly, the R0.1ZIS‐based cell delivers the open circuit potential of 1.587 V almost identical to the theoretical voltage, and an ultralow voltage gap of 0.71 V after undergoing 262 h operation. This work offers a promising avenue for building lattice–strain engineering to realize robust bifunctional electrocatalysts. [ABSTRACT FROM AUTHOR]

• The ORR and OER on bimetallic alloys encapsulated in fullerenes are studied by DFT. • C 50 and C 60 are the better carbon shell to encapsulate bimetallic alloys than C 40. • Co 1 Ni 3 @C 50 possesses the best ORR activity with the overpotential of 0.35 V. • Co 2 Ni 2 @C 60 has the most excellent OER activity with the overpotential of 0.36 V. [Display omitted] Revealing the structure-activity relationship of catalysts is conducive to design high-activity catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this paper, the ORR and OER catalytic activity of bimetallic alloys encapsulated in fullerenes M1 x M2 4− x @C n (M1 x M2 4− x represents Fe x Co 4− x , Fe x Ni 4− x , Co x Ni 4− x ; x = 1, 2, 3; n = 40, 50, 60) are investigated by density functional theory methods. The calculated encapsulation energy (E enc) indicates that except for the value on Fe 1 Ni 3 @C 60 , all the E enc values are positive on the studied M1 x M2 4− x @C n , suggesting that additional externally supplied energy will be needed to encapsulate bimetallic alloys in fullerenes. As the size of the C n cage decreases, the charge transfer between the alloy core and the carbon shell becomes greater, resulting in a roughly increase in the binding strength of the reaction intermediates on M1 x M2 4− x @C n. Compared with C 40 , C 50 and C 60 fullerenes are recognized as the more suitable shell for encapsulating bimetallic alloys toward ORR and OER. Based on the current study, Co 1 Ni 3 @C 50 is screened out with the best ORR activity (η ORR = 0.35 V) and Co 2 Ni 2 @C 60 shows the most excellent OER activity (η OER = 0.36 V) among all the M1 x M2 4− x @C n. [ABSTRACT FROM AUTHOR]

Developing efficient cathode catalysts can largely promote the application of Li‐O2 batteries (LOBs). In this work, the core‐shell MoS2−x@CNTs composite is synthesized via a hydrothermal method with annealing and NaBH4 reduction post‐processing, of which the defective MoS2 nanoflakes are homogeneously coated on the 3D carbon nanotube (CNT) webs. It is found that it delivers superior bifunctional catalytic activities toward both oxygen reduction and evolution reactions for LOBs. On the one hand, the charge re‐distribution on MoS2 nanoflakes with sulfur vacancies can be effectively constructed by the surface engineering strategy, remarkably boosting the kinetics of Li‐O2 catalysis. On the other hand, the conductive and high surface area CNT network can facilitate mass transfer and provide enough free space for composite cathodes, accommodating the volume changes caused by the reversible formation and decomposition of discharge products during cycling. More importantly, the unique core‐shell architecture can not only enable fully covering of defective MoS2 nanoflakes on CNT surfaces to avoid the contact between CNTs and electrolyte, distinctly suppressing side reactions, but also realize the exposure of more active sites to fulfill their catalytic properties. This work provides an insightful investigation on advanced catalysts and holds great potential for catalyst structural engineering in LOBs. [ABSTRACT FROM AUTHOR]

• Co 9 S 8 @NiCo 2 O 4 is prepared by hydrothermal and electrocatalytic deposited reaction. • Co 9 S 8 @NiCo 2 O 4 -10 cycles and Co 9 S 8 @NiCo 2 O 4 -70 cycles can serve as electrocatalytic water splitting catalysts. • Co 9 S 8 @NiCo 2 O 4 -10 cycles presents an excellent long-term electrochemical durability. Using Co 9 S 8 @NiCo 2 O 4 -10 cycles and Co 9 S 8 @NiCo 2 O 4 -70 cycles as a bifunctional water splitting catalyst, which overpotential of ~ 320 mV is obtained at a very low cell voltage of 1.55 V with a current density of 10 mA cm−2 in 1.0 M KOH. [Display omitted] The hydrogen and oxygen generation has been regarded as the most promising solution through electrochemical water splitting for the sake of alleviating the energy crisis and climate change. In this paper, we developed an in-situ deposition approach for depositing NiCo 2 O 4 on the surface of Co 9 S 8 , and then the loading amount of NiCo 2 O 4 was controlled by regulating the deposited number of cycles. In addition, the materials were used as catalysts for oxygen production and hydrogen production for the first time. When Co 9 S 8 @NiCo 2 O 4 -10 cycles, Co 9 S 8 @NiCo 2 O 4 -70 cycles and Co 9 S 8 is used as a bifunctional catalyst, Co 9 S 8 @NiCo 2 O 4 -70 cycles // Co 9 S 8 @NiCo 2 O 4 -10 cycles displays a smaller cell voltage (1.55 V@10 mA cm−2) than Co 9 S 8 (1.68 V@10 mA cm−2). Density functional theory calculation is used to calculate the water adsorption energy on the surface of the material to further reveal the reaction mechanism of water oxidation process. The work provides a new idea for the development of a relatively low toxicity and environmental friendly bifunctional electrocatalyst for industrial water electrolysis applications. [ABSTRACT FROM AUTHOR]

Single-atom catalysts (SACs) have been applied in many fields due to their superior catalytic performance. Because of the unique properties of the single-atom-site, using the single atoms as catalysts to synthesize SACs is promising. In this work, we have successfully achieved Co1 SAC using Pt1 atoms as catalysts. More importantly, this synthesis strategy can be extended to achieve Fe and Ni SACs as well. X-ray absorption spectroscopy (XAS) results demonstrate that the achieved Fe, Co, and Ni SACs are in a M1-pyrrolic N4 (M= Fe, Co, and Ni) structure. Density functional theory (DFT) studies show that the Co(Cp)2 dissociation is enhanced by Pt1 atoms, thus leading to the formation of Co1 atoms instead of nanoparticles. These SACs are also evaluated under hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and the nature of active sites under HER are unveiled by the operando XAS studies. These new findings extend the application fields of SACs to catalytic fabrication methodology, which is promising for the rational design of advanced SACs. Synthesizing single-atom catalysts through a general method presents a great challenge. Here the authors report that Fe, Co and Ni single-atom catalysts can be obtained using pre-located isolated Pt atoms as the catalyst and identify the role of Pt single atoms in the synthesis process. [ABSTRACT FROM AUTHOR]

Identifying real active sites and understanding the mechanism of oxygen evolution reaction (OER) are still a big challenge today for developing efficient electrochemical catalysts in renewable energy technologies. Here, using a combined in situ/operando experiments and theory, the catalytic mechanism of the ordered OER active Co and Ir ions in Sr2CoIrO6−δ is studied, which exhibits an unprecedented low overpotential 210 mV to achieve 10 mA cm–2, ranking the highest performance among perovskite‐based solid‐state catalysts. Operando X‐ray absorption spectroscopies as a function of applied voltage indicates that Ir4+ ion is gradually converted into extremely high‐valence Ir5+/6+, while the part of Co3+ ion is transferred into Co4+ under OER process. Density functional theory calculations explicitly reveal the order Co‐O‐Ir network as an origin of ultrahigh OER activity. The work opens a promising path to overcome the sluggish kinetics of OER bottleneck for water splitting via proper arrangements of the multi‐active sites in catalyst. [ABSTRACT FROM AUTHOR]

Recent years have witnessed an upsurge in the development of non-precious catalysts (NPCs) for alkaline water electrolysis (AWE), especially with the strides made in experimental and computational techniques. In this contribution, the most recent advances in NPCs for AWE were systematically reviewed, emphasizing the application of in situ/operando experimental methods and density functional theory (DFT) calculations in their understanding and development. First, we briefly introduced the fundamentals of the anode and cathode reaction for AWE, i.e., the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), respectively. Next, the most popular in situ/operando approaches for characterizing AWE catalysts, including hard and soft XAS, ambient-pressure XPS, liquid and identical location TEM, electrochemical mass spectrometry, and Raman spectroscopy were thoroughly summarized. Subsequently, we carefully discussed the principles, computational methods, applications, and combinations of DFT with machine learning for modeling NPCs and predicting the alkaline OER and HER. With the improved understanding of the structure–property–performance relationship of NPCs for AWE, we proceeded to overview their current development, summarising state-of-the-art design strategies to boost their activity. In addition, advances in various extensively investigated NPCs for AWE were evaluated. By conveying these methods, progress, insights, and perspectives, this review will contribute to a better understanding and rational development of non-precious AWE electrocatalysts for hydrogen production. [ABSTRACT FROM AUTHOR]

Catalysts are required for the oxygen evolution reaction, which are abundant, active, and stable in acid. MnO2 is a promising candidate material for this purpose. However, it dissolves at high overpotentials. Using first-principles calculations, a strategy to mitigate this problem by decorating undercoordinated surface sites of MnO2 with a stable oxide is developed here. TiO2 stands out as the most promising of the different oxides in the simulations. This prediction is experimentally verified by testing sputter-deposited thin films of MnO2 and Ti-MnO2. A combination of electrochemical measurements, quartz crystal microbalance, inductively coupled plasma mass spectrometry measurements, and X-ray photoelectron spectroscopy is performed. Small amounts of TiO2 incorporated into MnO2 lead to a moderate improvement in stability, with only a small decrease in activity. This study opens up the possibility of engineering surface properties of catalysts so that active and abundant nonprecious metal oxides can be used in acid electrolytes. [ABSTRACT FROM AUTHOR]