High-performance oxygen evolution electrocatalysis by boronized metal sheets with self-functionalized surfaces

885

551

The development of low-cost, high-efficiency, and robust electrocatalysts for the oxygen evolution reaction (OER) is urgently needed to address the energy crisis. In recent years, non-noble-metal-based OER electrocatalysts have attracted tremendous research attention. Beginning with the introduction of some evaluation criteria for the OER, the current OER electrocatalysts are reviewed, with the classification of metals/alloys, oxides, hydroxides, chalcogenides, phosphides, phosphates/borates, and other compounds, along with their advantages and shortcomings. The current knowledge of the reaction mechanisms and practical applications of the OER is also summarized for developing more efficient OER electrocatalysts. Finally, the current states, challenges, and some perspectives for non-noble-metal-based OER electrocatalysts are discussed.

Section: Classification Of the Non‐noble‐metal‐based Oer Electrocatalmentioning

confidence: 99%

Non‐Noble‐Metal‐Based Electrocatalysts toward the Oxygen Evolution Reaction

Zang

et al. 2020

885

551

“…In case of HER, this metric works well and gives a good comparison of the state‐of‐the‐art materials. However, being a multistep reaction, OER is often accompanied by oxidation of the catalytic species to produce intermediates, giving rise to a huge oxidation wave, spanning from a few µA cm −2 to tens of mA cm −2 . In such cases, the metric of 10 mA cm −2 is used precariously, leading to overestimated performances.…”

Section: Performance Evaluation and Related Discrepanciesmentioning

confidence: 99%

“…Liu et al used a solvothermal carbonization method to synthesize Co 2 B/Co/N–B–C/B 4 C hybrid catalyst which exhibited Co 2 B as well as Co metallic phases immobilized on graphitic carbon layers. Recently, a boronization strategy was developed to grow single phase metal boride layers on different metal substrates (Ni, Co, Fe, NiFe alloy, and SUS 304) . The synthesis method involved burying the metal substrate in boronizing agents (amorphous boron, potassium, fluoroborate), followed by thermal treatment in air at 800 °C.…”

Section: Synthesis Routes To Obtain Metal Boridesmentioning

confidence: 99%

Metal Boride‐Based Catalysts for Electrochemical Water‐Splitting: A Review

Gupta

Patel

Miotello

et al. 2019

314

243

Electrocatalytic water-splitting has gained a firm hold in the area of renewable hydrogen production owing to its integrative compatibility with intermittent energy sources. However, wide-scale implementation of this technology demands discovery of new electrode materials that strike a good balance between efficiency, stability, and cost. In the pool of inexpensive electrodes capable of catalyzing hydrogen and oxygen evolution reactions, metal borides/ borates have made a big splash in the last decade. However, the research in this family of electrocatalysts remains unorganized owing to the diversity of reports. This review summarizes the past and present research progress in metal borides/borates for electrocatalytic water-splitting. The fundamental reasons for electrochemical behavior in different metal borides/borates are highlighted here, also including some comments regarding erroneous practices in the performance evaluation of metal borides/borates. Various strategies used to enhance the electrocatalytic performance of metal borides/borates are discussed in detail. Different methods evolved over the years for the synthesis of metal borides/ borates are also discussed. Finally, an assessment of the commercial viability of metal borides/borates is made and future research directions are suggested. multimetal oxides, [18,19] layered double hydroxides, [20] oxyhydroxides, [21] and perovskites. [13,18] In addition to these, there has been the family of transition-metal borides/borates that have garnered enormous interest in the recent past. Though transition-metal borides (TMBs) have been used for water electrolysis since many decades, they were not really seen as potential candidates to replace noble metal catalysts, until recently. Indeed, in 2009, the group of Daniel Nocera reported in situ formed Co [22] and Ni [23] borates as analogous catalysts to Co phosphate, [24] for near-neutral water-splitting. Later, the groups of Hu [25] and Patel [26] reported development of Mo boride and Co boride, respectively, for electrocatalytic water splitting. Following these reports, transition-metal borides/ borates [27][28][29][30][31][32] were developed using various techniques and were used extensively for water-splitting reactions, in different pH solutions. Here, we would like to inform the readers that usually boron-based catalysts that are developed in situ using electrodeposition are referred to as "borates" (denoted as M-B i , M = metal) while those catalysts prepared by any other technique are referred to as "borides" (denoted as M-B). Over the past 5-6 years, a lot of studies have been carried out on borides/borates with remarkable results, presenting new possibilities in search for non-noble electrocatalysts. The electrochemical performance, stability and other important properties of all the metal borides reported so far are enlisted in Table 1 while that of metal borates are listed in Table 2. However, there are a lot of aspects that are not yet understood completely about borides/borates. For instance, the o...

“…During the OER process, the harsh basic condition at high anodic potential generally deteriorates the performance of catalysts due to the mechanical leaching of a sample from the conductive substrate, aggregation of the small cluster that lost the activity of active sites, chemical transformation into various inactive phases. [ 41 ] Controlled current electrolysis at 100 mA cm −2 was performed to evaluate the durability of the catalyst. As shown in Figure 5d the results show that the catalyst treated with NaBH 4 requires much lower potential to reach 100 mA cm −2 current density as compared to simple Gd‐CoB and CoB.…”

Section: Electrochemical Activitymentioning

confidence: 99%

Gold‐Supported Gadolinium Doped CoB Amorphous Sheet: A New Benchmark Electrocatalyst for Water Oxidation with High Turnover Frequency

Haq

Mansour

Munir

et al. 2020

Electrochemical water splitting has been considered a promising approach for green and sustainable hydrogen as a future energy carrier. However, the lack of high performance and inexpensive electrocatalysts for kinetically sluggish oxygen evolution reaction (OER) hinder the practical application. Here, the noteworthy enhancement of electrodeposited cobalt boride (CoB) nanosheets from the combined effect of using gadolinium as a dopant and thin film of gold as prudent support is demonstrated. The free-standing Gd-CoB@Au exhibits remarkable electrochemical performance, high intrinsic activity, and lower reaction resistance, which are confirmed by lower onset potential, small charge transfer resistance, lower Tafel slope value, and high turnover frequency. Furthermore, the post-OER characterization signpost, no observable change in the chemical structure or morphology of nanosheets during the long-lasting oxidation process. Because of the inexpensive, facile, and scalable one-step preparation processes, the catalyst is highly encouraging for large-scale practical applications.in pursuing toward viable electrochemical water splitting module. [1] The HER follows a relatively simple mechanism and various cost-effective and efficient metal/ alloy-based catalysts have been developed to produce hydrogen at fairly low overpotential. [2] A serious challenge, however, is the slow rate of multistep OER, which requires high activation energy and thus large overpotential to break OH bond, and to form an OO bond and transfer 04 electrons essentially required for oxygen evolution from two water molecules at the same time. [3] The slow rate of OER in turn adversely affects the overall rate of water splitting for hydrogen production. [4] It is, therefore, essentially required to develop stable, economical, and effective electrocatalysts for OER for the feasible production of H 2 by water splitting. Currently, IrO 2 and RuO 2 are the benchmark OER catalysts to significantly improve slow kinetics of oxygen evolution at the anode. These electrocatalysts are made up of expensive precious metals, and their supply is not sustainable and is, therefore, not much suitable for large-scale applications in water oxidation systems. [5] Besides precious metals, several costeffective nanoscale materials including layer double hydroxides, perovskite, amorphous/crystalline metal hydroxides have been extensively explored for OER. [6][7][8] Hence, it is well established, that nano-structuring is one of the widely adopted strategies to enhance the catalytic properties and selectivity, toward the OER for practical application. [9] However, low mass loading of catalyst, mechanical and chemical instability, less exposed surface area, reproducibility, potentially induced phase/electronic transformation during catalysis, surface leaching of the catalyst due to the low adhesion of catalyst are still serious concerns that need to be addressed. [10] Also, the use of powder nanomaterials traditionally needs various binders (Nafion/polymers) for the fabricati...