Cite this: J. Mater. Chem. A, 2024, 12, 6438
引用此文：J. Mater.Chem.A, 2024, 12, 6438

Received 6th November 2023
2023 年 11 月 6 日收到
Accepted 1st February 2024
2024 年 2 月 1 日接受
DOI:

10.1039 / d 3 ta 06794 g

Hollow structural materials derived from a MOFs/ polymer loaded CoRu alloy for significantly boosting electrochemical overall water splitting $†$
由 MOFs/聚合物负载 CoRu 合金衍生的中空结构材料可显著提高电化学整体水分离 $†$

Yin Hu, (D) Congcong Wang, Ying Liu, Hongyan Lin and Kai Zhang (1)*
Yin Hu、(D) Congcong Wang、Ying Liu、Hongyan Lin 和 Kai Zhang (1)*

Abstract 摘要

The development of efficient and stable bifunctional electrocatalysts for overall water splitting is essential to solve the energy crisis and environmental problems. Herein, the paper reports a CoRu@N-doped carbon hollow nanostructure (CoRu@NCHNS) material by using MOFs as precursors and adding dopamine (DA) to introduce Ru and N atoms and fabricate hollow structures in one step. Thanks to the synergistic effect of the CoRu alloy, unique hollow structure and $N$ atoms, the material achieves a current density of 10 $mA cm^{- 2}$ in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with very low overpotentials of 13 mV and 238 mV , respectively. In addition, an overall water splitting device was also assembled using CoRu@NCHNSs-8 h and CoRu@NCHNSs-9 h as the anode and cathode under alkaline conditions, and a current density of $10 mA cm^{- 2}$ was obtained at a cell voltage of 1.56 V . This work explores the applications of a hollow structure loaded CoRu alloy in overall water splitting and provides a new idea for the preparation of efficient electrocatalytic overall water splitting materials.
为解决能源危机和环境问题，开发高效稳定的整体水分离双功能电催化剂至关重要。本文报道了一种CoRu@N掺杂碳中空纳米结构（CoRu@NCHNS）材料，该材料以MOFs为前驱体，加入多巴胺（DA）引入Ru和N原子，一步制备出中空结构。由于 CoRu 合金、独特的中空结构和 $N$ 原子的协同作用，该材料在氢进化反应（HER）和氧进化反应（OER）中实现了 10 $mA cm^{- 2}$ 的电流密度，过电位分别为 13 mV 和 238 mV。此外，还利用 CoRu@NCHNSs-8 h 和 CoRu@NCHNSs-9 h 作为阳极和阴极，在碱性条件下组装了一个整体水分离装置，并在电池电压为 1.56 V 时获得了 $10 mA cm^{- 2}$ 的电流密度。这项工作探索了中空结构负载 CoRu 合金在整体水分离中的应用，为制备高效电催化整体水分离材料提供了新思路。

Introduction 导言

The rapid consumption of fossil energy will lead to a series of energy crises and environmental problems, and hydrogen energy has received a lot of attention from scientists as an efficient and clean energy source that is expected to replace traditional fossil energy sources.

^{1 - 3}

Electrolysis of water, consisting of two half-reactions, the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), is considered to be one of the most promising and sustainable methods for hydrogen production.

^{4 - 7}

Currently, the most efficient HER and OER electrocatalysts are Pt-based and Ir-based materials, but they are scarce and expensive, which has prompted a search for elements with similar properties to Pt but more abundant as catalysts.

^{8 - 10}

化石能源的快速消耗将导致一系列能源危机和环境问题，而氢能作为一种高效清洁的能源，有望取代传统的化石能源，因此受到科学家们的广泛关注。

^{1 - 3}

水的电解由氧进化反应（OER）和氢进化反应（HER）两个半反应组成，被认为是最有前途和最可持续的制氢方法之一。

^{4 - 7}

目前，最有效的 HER 和 OER 电催化剂是铂基和铱基材料，但它们稀缺且昂贵，这促使人们寻找与铂特性相似但更丰富的元素作为催化剂。

^{8 - 10}

In fact, various electrocatalysts based on transition metals and their derivatives (such as metal sulfide compounds,

^{11, 12}

metal phosphides,

^{13 - 15}

metal selenides,

^{16}

metal oxides,

^{17}

metal hydroxides,

^{18 - 20}

layered double hydroxides

^{21, 22}

and so on) have been investigated as bifunctional electrocatalysts for overall water splitting, and significant progress has been made. In our previous work, CoP@NCHNCs were prepared and showed good OER and HER activities at

10 mA cm^{- 2}

requiring only low overpotentials of 304 mV and 93 mV . CoP@NCHNCs can be
事实上，各种基于过渡金属及其衍生物（如金属硫化物、

^{11, 12}

金属磷化物、

^{13 - 15}

金属硒化物、

^{16}

金属氧化物、

^{17}

金属氢氧化物、

^{18 - 20}

层状双氢氧化物

^{21, 22}

等）的电催化剂已作为整体水分离的双功能电催化剂进行了研究，并取得了重大进展。在我们之前的工作中，制备了 CoP@NCHNCs 并在

10 mA cm^{- 2}

条件下显示出良好的 OER 和 HER 活性，只需要 304 mV 和 93 mV 的低过电位。CoP@NCHNCs 可以

used as the anode and cathode up to

10 mA cm^{- 2}

1.62 V .^{23}

However, due to the complexity of the preparation process and the generation of toxic substances, further optimization is still required. D. Jason Riley and colleagues synthesized a

Ni -

Co@Fe-Co PBA material that exhibited significant electrocatalytic HER performance in alkaline freshwater and simulated seawater with overpotentials of 43 and 183 mV , respectively.

^{24}

However, due to single function and poor activity, this catalyst still cannot meet the needs of practical applications. Therefore, it is still challenging to develop efficient electrocatalytic materials for overall water splitting.

10 mA cm^{- 2}

时用作阳极和阴极，但由于制备过程复杂且会产生有毒物质，因此仍需进一步优化。D. Jason Riley 及其同事合成了一种

Ni -

Co@Fe-Co PBA 材料，该材料在碱性淡水和模拟海水中表现出显著的电催化 HER 性能，过电位分别为 43 mV 和 183 mV。

^{24}

然而，由于功能单一、活性差，这种催化剂仍不能满足实际应用的需要。因此，开发用于整体水分离的高效电催化材料仍具有挑战性。

Ruthenium, a platinum-based metal, has similar properties to Pt but is about

1 / 30

of the price. Many studies have demonstrated that Ru has excellent adsorption capacity for both OER and HER intermediates.

^{25, 26}

By the synergistic effect of transition metals and ruthenium, it is possible to achieve both a lower cost and a significant increase in catalytic activity, and is expected to be a bifunctional catalyst.

^{27, 28}

For example, Chen and colleagues have designed a cobalt single atom incorporated in a ruthenium oxide sphere material, using a Co single atom to modify the electronic structures of the surrounding Ru atoms and thereby remarkably elevate the electrocatalytic activities. The catalyst requires ultralow overpotentials, 45 mV for the HER and 200 mV for the OER, to deliver a current density of 10 mA

{cm}^{- 2}

^{29}

钌是一种铂基金属，具有与铂相似的特性，但价格仅为铂的

1 / 30

左右。许多研究表明，Ru 对 OER 和 HER 中间体都具有出色的吸附能力。

^{25, 26}

通过过渡金属和钌的协同作用，既可以降低成本，又可以显著提高催化活性，有望成为一种双功能催化剂。

^{27, 28}

例如，Chen 及其同事设计了一种在氧化钌球材料中加入钴单原子的催化剂，利用钴单原子改变周围 Ru 原子的电子结构，从而显著提高电催化活性。该催化剂需要超低的过电位（HER 为 45 mV，OER 为 200 mV），以提供 10 mA

{cm}^{- 2}

的电流密度。

^{29}

Usually, the introduction of Ru into transition metal MOF materials was performed by ion exchange. The MOFs are immersed in a solution of

{Ru}^{3 +}

, and subsequently the MOFs are etched to allow the

{Ru}^{3 +}

to be exchanged with the transition metal.

^{30, 31}

For example, Qi et al. synthesized heterostructured
通常，通过离子交换将 Ru 引入过渡金属 MOF 材料中。将 MOFs 浸入

{Ru}^{3 +}

溶液中，然后对 MOFs 进行蚀刻，使

{Ru}^{3 +}

与过渡金属发生交换。

^{30, 31}

例如，Qi 等人合成了异质结构的
inter-doped ruthenium-cobalt oxide

[(Ru - Co) O_{x}]

hollow nanosheet arrays by this method.

^{32}

Electrodeposition was also an effective method to introduce Ru.

^{33}

For example, Zhao et al. synthesized

{Ru}^{- {Pt}_{rich} Co}

nanowires by electrodeposition.

^{34}

In addition to this, in situ growth and template methods were also some common approaches.

^{35, 36}

However, these methods were either atomically underutilized or difficult to carry out. There is an urgent need to find a new and efficient method. It is well known that dopamine (DA) has a strong coordination effect on metals, and the use of dopamine to introduce Ru can greatly improve atomic utilization.

^{37, 38}

At the same time, dopamine is rich in N , and at high temperatures, it can generate pyrrole N and pyridine N to improve the electrical conductivity and modulate the electronic structure of materials.

^{23, 39, 40}

Therefore, it is widely used as a ligand for electrocatalysts.

[(Ru - Co) O_{x}]

空心纳米片阵列。

^{32}

电沉积也是引入 Ru 的有效方法。

^{33}

例如，Zhao 等人通过电沉积合成了

{Ru}^{- {Pt}_{rich} Co}

纳米线。

^{34}

除此之外，原位生长法和模板法也是一些常用的方法。

^{35, 36}

然而，这些方法要么原子利用率低，要么难以实施。因此迫切需要找到一种新的高效方法。众所周知，多巴胺（DA）对金属有很强的配位作用，利用多巴胺引入 Ru 可以大大提高原子利用率。

^{37, 38}

同时，多巴胺富含N，在高温下可生成吡咯N和吡啶N，从而提高材料的导电性和调控材料的电子结构。

^{23, 39, 40}

因此，它被广泛用作电催化剂的配体。

In summary, this manuscript describes the synthesis of an N-doped carbon hollow nanostructure material (CoRu@NCHNSs) based on a composite of MOFs and PDA. The material possesses a hollow structure and is loaded with the CoRu alloy. ZIF-67 provided the template and the transition metal. DA was polymerized while disassembling ZIF-67 to form a hollow structure, while introducing N atoms and utilizing strong coordination to enhance the Ru payload in one step. The hollow structure exposes more metal active sites; the introduction of N atoms improves the electrical conductivity; the introduction of small amounts of Ru induces the formation of the CoRu alloy, which greatly improves the electrocatalytic performance of the material and provides a new idea for the preparation of efficient electrocatalytic overall water splitting materials.
综上所述，本手稿介绍了一种基于 MOFs 和 PDA 复合材料的掺 N 碳中空纳米结构材料（CoRu@NCHNSs）的合成。该材料具有中空结构，并负载有 CoRu 合金。ZIF-67 提供了模板和过渡金属。在分解 ZIF-67 形成中空结构的同时，对 DA 进行了聚合，同时引入了 N 原子，并利用强配位一步到位地提高了 Ru 的有效载荷。中空结构暴露了更多的金属活性位点；N原子的引入提高了导电性；少量Ru的引入诱导形成了CoRu合金，大大提高了材料的电催化性能，为制备高效电催化整体分水材料提供了新思路。

Experimental 实验性

It has been provided in the ESI.

†

它已在 ESI 中提供。

†

Results $&$ discussion
结果 $&$ 讨论

Synthesis and characterization
合成与表征

A typical synthetic route of CoRu@NCHNSs is illustrated in Fig. 1a (for details see the ESI

†

). Taking CoRu@NCHNSs-9 h as an example, first, purple ZIF-67 solid powder was synthesized by leaving

Co {({NO}_{3})}_{2} \cdot 6 H_{2} O

and 2-methylimidazole in methanol solution for 12 hours. Transmission electron microscopy (TEM) showed that ZIF-67 had a regular dodecahedral morphology with a size of 300-500 nm (Fig. 1b), which could also be seen by scanning electron microscopy (Fig. S1a

†

). Subsequently, ZIF-67 was dispersed in methanol, and dopamine (DA) and

{RuCl}_{3}^{-}

\cdot x H_{2} O

were added and refluxed at

60^{\circ} C

for 9 h to produce

CoRu / PDA

HNSs- 9 h . The strong coordination between monomer DA and cobalt ions disassembled the structure of ZIF-67 and released alkaline 2 -methylimidazole, and the alkaline conditions triggered the polymerization of DA on the surface of ZIF-67 to form a polydopamine (PDA) shell.

^{41, 42}

Moreover,

{Ru}^{3 +}

was also introduced into the PDA shell due to the strong coordination between DA and Ru ions. Finally, hollow CoRu/PDA HNS materials loaded with Co and Ru ions were generated. CoRu/PDA HNSs-9 h was pyrolyzed at

750^{\circ} C

under an Ar
CoRu@NCHNSs 的典型合成路线如图 1a 所示（详见 ESI

†

）。以 CoRu@NCHNSs-9 h 为例，首先将

Co {({NO}_{3})}_{2} \cdot 6 H_{2} O

和 2-甲基咪唑在甲醇溶液中放置 12 小时，合成紫色 ZIF-67 固体粉末。透射电子显微镜（TEM）显示，ZIF-67具有规则的十二面体形态，大小为300-500 nm（图1b），扫描电子显微镜也可以看到这种形态（图S1a

†

）。随后，将 ZIF-67 分散在甲醇中，加入多巴胺（DA）和

{RuCl}_{3}^{-}

\cdot x H_{2} O

并在

60^{\circ} C

下回流 9 小时，制得

CoRu / PDA

HNSs- 9 小时。单体DA与钴离子之间的强配位分解了ZIF-67的结构，释放出碱性的2-甲基咪唑，碱性条件引发了DA在ZIF-67表面的聚合，形成多巴胺（PDA）外壳。

^{41, 42}

此外，由于DA和Ru离子之间的强配位，

{Ru}^{3 +}

也被引入到PDA外壳中。最后，负载有 Co 和 Ru 离子的中空 CoRu/PDA HNS 材料诞生了。CoRu/PDA HNSs-9 h 在

750^{\circ} C

Ar
atmosphere to obtain CoRu@NCHNSs-9 h powder. The TEM image (Fig. 1c) and the breakage of the samples in the SEM image (Fig. S1b

†

) indicated that CoRu/PDA HNSs-9 h mostly maintained the original ZIF-67 morphology and had an obvious hollow structure. However, the surface of CoRu/PDA HNSs-9 h was rough, which was caused by the generation of small PDA particles. After pyrolysis, CoRu@NCHNSs-9 h still retained a hollow structure (Fig. 1d and S1c

†

), which could expose more active sites. A large number of nanoparticles was generated, which was due to the ability of the organic ligand to act as a reducing agent at high temperatures, reducing metal ions to metal monomers and nanoparticles to improve the electrical conductivity.

^{43 - 46} 0.21

and 0.23 nm lattice spacings could be observed in HR-TEM images (Fig. 1e), which was attributed to hexagonal CoRu (002) and CoRu (100) facets,

^{28, 47 - 49}

and indicated that MOFs and a PDA shell could act as a growth template for CoRu alloy NPs. In addition, EDS elemental mapping further confirmed the uniform distribution of

Ru, Co

and N atoms in the material (Fig.

S 2 †

), and illustrated the successful introduction of Ru and N .
气氛下获得 CoRu@NCHNSs-9 h 粉末。TEM 图像（图 1c）和 SEM 图像（图 S1b

†

）中样品的破损情况表明，CoRu/PDA HNSs-9 h 大部分保持了原始的 ZIF-67 形貌，具有明显的中空结构。但是，CoRu/PDA HNSs-9 h 的表面比较粗糙，这是由于产生了小的 PDA 颗粒。热解后，CoRu@NCHNSs-9 h 仍保持中空结构（图 1d 和 S1c

†

），这可能暴露了更多的活性位点。由于有机配体能够在高温下充当还原剂，将金属离子还原成金属单体和纳米粒子，从而提高导电性，因此产生了大量纳米粒子。在 HR-TEM 图像（图 1e）中可以观察到

^{43 - 46} 0.21

和 0.23 nm 的晶格间距，这归因于六方 CoRu (002) 和 CoRu (100) 面，

^{28, 47 - 49}

并表明 MOFs 和 PDA 外壳可以作为 CoRu 合金 NPs 的生长模板。此外，EDS 元素图谱进一步证实了

Ru, Co

和 N 原子在材料中的均匀分布（图

S 2 †

），并说明了 Ru 和 N 的成功引入。

Subsequently, a series of products at different reaction times were synthesized, CoRu@NCHNSs-7 h, CoRu@NCHNSs-8 h and CoRu@NCHNSs-10 h. It could be seen that all the CoRu/PDA HNSs were able to maintain a similar hollow structure, although the PDA shell became thicker as the reaction proceeded from 7 h to 9 h (Fig. S3a-d

†

). However, when the reaction proceeded to 10 h , the hollow structure was no longer independent, and the shells aggregated together. This also led to the collapse of the hollow CoRu@NCHNSs-10 h after pyrolysis (Fig. S3e and

f^{†}

). As a comparison, using a similar preparation approach, Co@NCHNSs-9 h without

{RuCl}_{3} \cdot x H_{2} O

and ZnRu@NCHNSs-9 h with a similar size ZIF-8 as the template were also prepared. In short, they both had similar hollow structures (Fig. S4 and S5

†

).
随后，合成了一系列不同反应时间的产物，分别为CoRu@NCHNSs-7 h、CoRu@NCHNSs-8 h和CoRu@NCHNSs-10 h。可以看出，所有的CoRu/PDA HNS都能够保持相似的中空结构，尽管随着反应从7 h进行到9 h，PDA外壳变得更厚（图S3a-d

†

）。然而，当反应进行到 10 小时时，中空结构不再独立，外壳聚集在一起。这也导致了热解 10 h 后中空 CoRu@NCHNSs 的坍塌（图 S3e 和

f^{†}

）。作为对比，使用类似的制备方法，还制备了不含

{RuCl}_{3} \cdot x H_{2} O

的 Co@NCHNSs-9 h 和以类似尺寸的 ZIF-8 为模板的 ZnRu@NCHNSs-9 h。总之，它们都具有相似的中空结构（图 S4 和 S5

†

）。

X-ray photoelectron spectroscopy (XPS) measurements of CoRu@NCHNSs-9 h, Co@NCHNSs-9 h and ZnRu@NCHNSs-9 h were conducted to investigate the element composition and altered surface electronic structures. The XPS survey spectrum of CoRu@NCHNSs-9 h revealed the presence of Co, Ru, O, N and C elements (Fig. 2a). Similarly, the presence of C, N, O, Zn and Ru could also be observed in ZnRu@NCHNSs-9 h (Fig. S6

†

) and the presence of C, N, O and Co, in Co@NCHNSs-9 h (Fig.

S 7 †

). As shown in Fig. 2b, the N1s spectra of CoRu@NCHNSs-9 h had 4 characteristic peaks at 399.17 eV ,

400.47 eV, 401.05 eV

, and 401.74 eV , corresponding to pyridine N , pyrrole N , graphitized N and

N - H

bonds, respectively.

^{28, 30, 49}

The interaction of Co and Ru was investigated by comparing the high-resolution XPS spectra of CoRu@NCHNSs-9 h, ZnRu@NCHNSs-9 h and Co@NCHNSs-9 h. First, the Co

2 p_{3 / 2}

characteristic peaks in the high-resolution Co 2p XPS spectrum of CoRu@NCHNSs-9 h were at 779.16 eV and 780.70 eV , which were attributed to

{Co}^{0}

and

{Co}^{2 +}

species (Fig. 2b),

^{49 - 51}

respectively. It was shifted to a higher binding energy than the

{Co}^{2 +}

peak ( 780.39 eV ) in Co@NCHNSs-9 h (Fig. S8b

†

), which was mainly due to the electron transfer from Co to Ru in the CoRu alloy. And the high-resolution XPS spectrum of Ru 3p in CoRu@NCHNSs-9 h showed that Ru3p

p_{3 / 2}

shifted toward a lower
对 CoRu@NCHNSs-9 h、Co@NCHNSs-9 h 和 ZnRu@NCHNSs-9 h 进行了 X 射线光电子能谱（XPS）测量，以研究元素组成和改变的表面电子结构。CoRu@NCHNSs-9 h 的 XPS 勘测光谱显示了 Co、Ru、O、N 和 C 元素的存在（图 2a）。同样，在 ZnRu@NCHNSs-9 h 中也可以观察到 C、N、O、Zn 和 Ru 元素的存在（图 S6

†

），在 Co@NCHNSs-9 h 中也可以观察到 C、N、O 和 Co 元素的存在（图

S 7 †

）。如图 2b 所示，CoRu@NCHNSs-9 h 的 N1s 光谱在 399.17 eV、

400.47 eV, 401.05 eV

和 401.74 eV 处有 4 个特征峰，分别对应于吡啶 N、吡咯 N、石墨化 N 和

N - H

键。

^{28, 30, 49}

通过比较 CoRu@NCHNSs-9 h、ZnRu@NCHNSs-9 h 和 Co@NCHNSs-9 h 的高分辨率 XPS 光谱，研究了 Co 和 Ru 的相互作用。首先，CoRu@NCHNSs-9 h 的高分辨率 Co 2p XPS 光谱中的 Co

2 p_{3 / 2}

特征峰分别位于 779.16 eV 和 780.70 eV，分别归因于

{Co}^{0}

和

{Co}^{2 +}

物种（图 2b），

^{49 - 51}

。在 Co@NCHNSs-9 h 中，它比

{Co}^{2 +}

峰 ( 780.39 eV ) 移动到了更高的结合能（图 S8b

†

），这主要是由于 CoRu 合金中电子从 Co 转移到了 Ru。而 CoRu@NCHNSs-9 h 中 Ru 3p 的高分辨率 XPS 光谱显示，Ru3p

p_{3 / 2}

向更低的位置移动。

Fig. 1 (a) Schematic illustration of the synthesis of the CoRu@NCHNSs, (b-d) TEM images of ZIF-67, CoRu/PDA HNSs-9 h and CoRu@NCHNSs9 h , and (e) HR-TEM image of CoRu@NCHNSs-9 h.
图 1 (a) CoRu@NCHNSs 的合成示意图；(b-d) ZIF-67、CoRu/PDA HNSs-9 h 和 CoRu@NCHNSs-9 h 的 TEM 图像；(e) CoRu@NCHNSs-9 h 的 HR-TEM 图像。
binding energy than ZnRu@NCHNSs-9 h (Fig. S8a

†

^{52, 53}

This indicated that the electronic interaction between Co and Ru was stronger than that between Zn and Ru .
图 S8a

†

）。

^{52, 53}

这表明 Co 和 Ru 之间的电子相互作用强于 Zn 和 Ru 之间的相互作用。

Furthermore, XRD was subsequently performed to investigate the composition and crystalline structure of the catalysts (Fig. 3). It could be found that CoRu/PDA HNSs-9 h did not maintain the crystalline structure of the original ZIF-67, and a diffuse scattering peak could be clearly observed at

\sim 20^{\circ}

, which was attributed to the amorphous polymer PDA.

^{23}

After pyrolysis at

750^{\circ} C

, the signal peak of Co@NCHNSs- 9 h at

{44.2}^{\circ}

corresponds well to the cubic Co (PDF# 15-0806) (111) facet, while CoRu/PDA HNSs-9 h exhibited another peak at

{45.8}^{\circ}

corresponding to the (101) facet of hexagonal CoRu (PDF# 658976), indicating that CoRu/PDA HNSs-9 h had not only cubic Co but also hexagonal CoRu , and the introduction of ruthenium could change cubic Co crystallinity to hexagonal CoRu. There were no obvious signal peaks of crystalline Ru which indicated that Ru mostly formed a CoRu alloy. The XRD signal peaks of
此外，为了研究催化剂的组成和结晶结构，还进行了 XRD 分析（图 3）。可以发现，CoRu/PDA HNSs-9 h 并未保持原始 ZIF-67 的结晶结构，在

\sim 20^{\circ}

处可以清晰地观察到漫散射峰，该峰归因于无定形聚合物 PDA。

^{23}

在

750^{\circ} C

处热解后，Co@NCHNSs- 9 h 在

{44.2}^{\circ}

处的信号峰与立方 Co（PDF# 15-0806）（111）面很好地对应，而 CoRu/PDA HNSs-9 h 在

{45.8}^{\circ}

处显示出另一个峰，与六方 CoRu（PDF# 658976）的（101）面对应、这表明 CoRu/PDA HNSs-9 h 不仅含有立方 Co，还含有六方 CoRu，而钌的引入可将立方 Co 的结晶性改变为六方 CoRu。结晶 Ru 没有明显的信号峰，这表明 Ru 大部分形成了 CoRu 合金。钌的 XRD 信号峰

ZnRu@NCHNSs-9 h correspond well to hexagonal Ru (PDF# 894903), which indicated that

{Ru}^{3 +}

was mostly transformed into Ru nanoparticles in the ZnRu@NCHNSs-9 h catalyst (Fig. S9†).
ZnRu@NCHNSs-9 h 与六方 Ru（PDF# 894903）对应良好，这表明

{Ru}^{3 +}

在 ZnRu@NCHNSs-9 h 催化剂中大部分转化为 Ru 纳米颗粒（图 S9†）。

Hydrogen evolution reaction
氢进化反应

The HER catalytic activity of different catalysts was measured in 1 M KOH solution at room temperature using a typical threeelectrode system without iR-correction. The linear sweep voltammetry (LSV) curves of all samples are illustrated in Fig. 4a. CoRu@NCHNSs-9 h showed the best HER catalytic activity in a basic electrolyte; it could reach a current density of 10 mA

{cm}^{- 2} (η 10)

at an overpotential of 13 mV , which was lower than that of ZnRu@NCHNSs-9 h of 18 mV and much lower than that of Co@NCHNSs-9 h of 118 mV . This indicated that the introduction of Ru can greatly improve the HER catalytic activity, the Ru site was the intrinsic active site of the HER and the synergistic effect of the CoRu alloy was better than that of the ZnRu alloy. The performance comparison of the materials at different
室温下，在 1 M KOH 溶液中使用典型的三电极系统测量了不同催化剂的 HER 催化活性，没有 iR 校正。图 4a 展示了所有样品的线性扫频伏安法（LSV）曲线。在碱性电解质中，CoRu@NCHNSs-9 h 的 HER 催化活性最好；在 13 mV 的过电位下，其电流密度可达 10 mA

{cm}^{- 2} (η 10)

，低于 ZnRu@NCHNSs-9 h 的 18 mV，也远低于 Co@NCHNSs-9 h 的 118 mV。这表明 Ru 的引入可以大大提高 HER 的催化活性，Ru 位点是 HER 的固有活性位点，CoRu 合金的协同效应优于 ZnRu 合金。材料在不同条件下的性能比较

Fig. 2 (a) Survey scan of CoRu@NCHNSs-9

h

and (

b - d

) high-resolution XPS spectra of Co

2 p

, Ru

3 p

, and

N

1s.
图 2 (a) CoRu@NCHNSs-9

h

和 (

b - d

) Co

2 p

、Ru

3 p

和

N

1s 的高分辨率 XPS 光谱的勘测扫描。
reaction times showed that CoRu@NCHNSs-8 h , CoRu@NCHNSs-9 h and CoRu@NCHNSs-10 h showed a volcano-type trend, with a large degree of decay at 10 h , mainly due to the destruction of the hollow structure. This further showed that the hollow structure played an important role in
反应时间表明，CoRu@NCHNSs-8 h、CoRu@NCHNSs-9 h和CoRu@NCHNSs-10 h呈现火山型趋势，10 h时衰减程度较大，主要原因是中空结构被破坏。这进一步表明，中空结构在
the catalytic performance of materials. It was noteworthy that the HER activity of CoRu@NCHNSs-9 h in alkaline media was particularly excellent among those of already reported highly efficient HER electrocatalysts (Table S1

†

).
材料的催化性能。值得注意的是，在已报道的高效 HER 电催化剂中，CoRu@NCHNSs-9 h 在碱性介质中的 HER 活性尤其出色（表 S1

†

）。

Fig. 3 (a) XRD patterns of ZIF-67, CoRu/PDA HNSs-9 h and CoRu@NCHNSs-9 h and (b) XRD patterns of CoRu@NCHNSs-7 h, CoRu@NCHNSs-8 h, CoRu@NCHNSs-10 h and Co@NCHNSs-9 h.
图 3 (a) ZIF-67、CoRu/PDA HNSs-9 h 和 CoRu@NCHNSs-9 h 的 XRD 图样；(b) CoRu@NCHNSs-7 h、CoRu@NCHNSs-8 h、CoRu@NCHNSs-10 h 和 Co@NCHNSs-9 h 的 XRD 图样。

Fig. 4 (a) LSV curves of different samples for the HER in 1 M KOH , (b) corresponding Tafel curves, © capacitive currents against the scan rate and corresponding

C_{d l}

value, and (d) HER stability test of CoRu@NCHNSs-9 h.
图 4 (a) 不同样品在 1 M KOH 中的 HER LSV 曲线；(b) 相应的 Tafel 曲线、© 电容电流与扫描速率的关系以及相应的

C_{d l}

值；(d) CoRu@NCHNSs-9 h 的 HER 稳定性测试。

In addition, the CoRu@NCHNSs-9 h catalyst exhibited the smallest Tafel slope of only

69.4 mV dec^{- 1}

, which indicated optimal HER kinetics (Fig. 4b).

^{54}

The electrode kinetics of the catalyst during the HER was investigated by electrochemical impedance spectroscopy (EIS),

^{55, 56}

and the semicircle in the mid-frequency range reflected the charge transfer resistance (

R_{ct}

) (Fig. S10

†

). The smallest

R_{ct}

Hollow structural materials derived from a MOFs/ polymer loaded CoRu alloy for significantly boosting electrochemical overall water splitting † † †\dagger由 MOFs/聚合物负载 CoRu 合金衍生的中空结构材料可显著提高电化学整体水分离 † † †\dagger