Towards designing efficient catalyst for hydrogen oxidation reaction
来源期刊：Rare Metals2020年第10期
论文作者：Rui-Jie Gao Ji-Jun Zou
文章页码：1107 - 1109
摘 要：<正>Anion exchange membrane fuel cells （AEMFCs） have attracted increasing research efforts in the past decade due to the advantageous nature of using Pt-free catalysts and cheap components that bring its cost closer to the target of US$30 kW-1[1].On the aspect of cathodic oxygen reduction reaction （ORR）,several Pt-free catalysts (such as
Towards designing efficient catalyst for hydrogen oxidation reaction
Rui-Jie Gao Ji-Jun Zou
Key Laboratory for Green Chemical Technology of the Ministry of Education,School of Chemical Engineering and Technology,Tianjin University
Collaborative Innovative Center of Chemical Science and Engineering(Tianjin)
作者简介：*Ji-Jun Zou,e-mail:jj_zou@tju.edu.cn;
Towards designing efficient catalyst for hydrogen oxidation reaction
Rui-Jie Gao Ji-Jun Zou
Key Laboratory for Green Chemical Technology of the Ministry of Education,School of Chemical Engineering and Technology,Tianjin University
Collaborative Innovative Center of Chemical Science and Engineering(Tianjin)
Anion exchange membrane fuel cells (AEMFCs) have attracted increasing research efforts in the past decade due to the advantageous nature of using Pt-free catalysts and cheap components that bring its cost closer to the target of US$30 kW-1
[
1]
.On the aspect of cathodic oxygen reduction reaction (ORR),several Pt-free catalysts (such as M-N-C
[
2]
and transition metal oxides
[
3,
4]
) are developed,and their performance can be comparable to that of Pt-based catalysts.Yet anodic hydrogen oxidation reaction(HOR) is still challenging,due to the main reliance on Ptbased catalysts and two-order slow kinetics in alkaline electrolyte.It has been proved that the HOR activity is in a positive correlation with the oxophilicity and hydrogen binding energy (HBE) of catalysts
[
5]
.In order to construct efficient HOR catalysts,regulating the d-band of metals can be potentially used to moderate the binding affinity towards O and H species.Tuning the adsorption of intermediate species is very effective to enhance the electrocatalysis
[
6]
.Particularly for HOR,nickel is a potential alternative to Pt-based catalysts,but its unfavourable d-band can cause the strong binding affinity towards H and O species,which block the active sites.By means of electron transfer effect,the d-band centre of Ni is downshifted by N-coupling,which weakens the binding energy of H and O species and thus results in remarkable HOR activity and stability
[
7,
8]
.However,the HOR activities ofNi-based catalysts are still far away from that of Pt,insufficient rendering them practically viable.Notably,the strong interaction between active sites and support (metal oxides) can also regulate the electronic structure
[
6,
9]
,which further optimizes the adsorption of intermediate species and ultimately enhances the catalytic performance.Recently,one paper published in Nature Catalysis reported an efficient Ru HOR catalyst whose activity approaches Pt
[
10]
.
Zhou et al.
[
10]
synthesized Ru clusters partially confined in the lattice of urchin-like TiO2 crystals (denoted Ru@TiO2) and demonstrated the formation of abundant Ru-Ti bond due to the atomic grow of Ru along the lattice of TiO2 (Fig.1a-f).In Ru@TiO2,efficient electron transfer from electron-rich TiO2 to Ru clusters was observed,and thus,4d bands of Ru were highly occupied,which could significantly decrease the adsorption of surface species (H,OH,and CO) on Ru.As a result,the weaken surface oxophilicity and HBE could contribute to the expose of more active Ru atoms and enhanced HOR kinetics,respectively.Ru@TiO2 efficiently catalysed the HOR up to a potential of 0.9 V (vs.RHE) with mass activities of 380and 282 A·g-1 for Au in acidic and alkaline media,respectively,which were～15%-30%higher than those of a PtRu catalyst (300 A·g-1 for precious metal in acid and 244 A·g-1 for precious metal in base,Fig.1g-i).This catalyst also exhibited an unexpected CO tolerance with undisturbed HOR activity in the presence of 1000×10-6CO and even at a CO content of 10 vol%(Fig.1j,k).Furthermore,it was quite stable with the current density decays of<3%and 10.6%tested on RDE and GDE,respectively.
This work proves the positive correlation between the binding affinity of surface species and d-band of metals andsuggests that electronic structure of metal nanoparticles can be regulated by oxides.Moreover,it provides a highly efficient Pt-free HOR catalyst,which has greatly potential applications in AEMFCs.However,the stability of Ru@TiO2 is insufficient due to the partial oxidation of Ru under the harsh conditions,which requires more work to further enhance the stability.
Fig.1 a HRTEM image of Ru@TiO2,b enlarged view of interface between Ru and TiO2;selected area FFT patterns of c Ru and e TiO2;inverse FFT patterns of d Ru and f TiO2;polarization curves of Ru@TiO2,PtRu/Ccom and Ru/C catalysts in H2-saturated g 0.1 mo1·L-1 KOH and h 0.1 mol·L-1 HClO4 solutions at a scan rate of 10 mV·s-1 and rotation speed of 1600 r·min-1;i precious metal mass activities at 20 mV;j polarization curves of Ru@TiO2 and PtRu/Ccom in H2/1000 r·min-1 CO-saturated 0.1 mol·L-1 KOH solution at a scan rate of 10 mV·s-1 and rotation speed of 1600 r·min-1;k polarization curves of Ru@TiO2,PtRu/Ccom (Ccom represents commercial carbon black) and Ru/C in0.1 mol·L-1 KOH solution (H2:CO volume ratio of 10:1) at a scan rate of 10 mV·s-1 and rotation speed of 1600 r·min-1 (reproduced from Ref.
[10]with permission from Springer Nature,Copyright 2020)
