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  贵金å±?span style="font-family:;">Ptå› å…¶å…ähœ‰åˆé€‚的费米能çñ”而被用作常用的助催化剂，å…ähœ‰‹zÀL€§é«˜ã€ç¨³å®šæ€§å¥½½{‰ä¼˜åŠÑ€‚作为助催化剂，Pt的化学状态对光催化剂的析氢活性有显著影响åQŒä½†˜q™ç§å½±å“ž®šæœªå¾—到深入研究。更为重要的是，了解Pt在光催化反应˜q‡ç¨‹ä¸­çš„真实性质åQŒå¯ä»¥äؓ构徏å…ähœ‰é«˜æ´»æ€§çš„光催化剂提供新的思èµ\ã€?/span> ˜q‘期åQŒä¸­å›½çŸ³æ²¹å¤§å­¦ï¼ˆåŒ—京åQ‰çŽ‹é›…君副研½I¶å‘˜è¯ùN¢˜¾l„与清华大学朱永法教授在ã€?/span>Chemical Engineering Journalã€?/span>期刊上发表了题äØ“â€?/span>Boosting photocatalytic hydrogen evolution via regulating Pt chemical states”的文章åQ?span style="font-family:;">DOIåQ?/span>10.1016/j.cej.2022.136334åQ‰ã€‚本论文提出了一¿Uæœ‰æ•ˆçš„½{–ç•¥åQŒé€šè¿‡è°ƒèŠ‚Pt的化学状态来大幅度提é«?/span>Pt/g-C3N4光催化剂的äñ”氢性能。文中制备了不同Pt0含量çš?/span>Pt/g-C3N4催化剂，发现提高Pt0含量可以大幅提高光解水äñ”氢活性。原位红外光谱和DFT理论计算证明åQŒæ°”æ°?/span>处理使电(sh¨´)子从g-C3N4çš?/span>N原子转移åˆ?/span>Pt2 ä¸?/span>åQŒä»Žè€Œå¢žåŠ äº†Pt0物种的数量ã€?/span>Pt0物种的大量生成有利于加速光生电(sh¨´)èïLš„分离。此外，Pt0æ¯?/span>Pt2 å…ähœ‰æ›´ä½Žçš„氢气吸附能åQŒæœ‰åˆ©äºŽæ°¢æ°”的溢出。因此，å…ähœ‰é«˜æ¯”ä¾?/span>Pt0的光催化剂具有更高的产氢‹zÀL€§ã€?/span>


  本文采用了高温热聚合、超声湿‹¹¸æ¸åQ?/span>1.0%-Pt/CNåQ‰ã€å…‰æ²‰ç§¯åQ?/span>1.0%-Pt/CN-PåQ‰ã€?/span>NaBH4液相˜q˜åŽŸåQ?/span>1.0%-Pt/CN-BHåQ‰å’Œæ°¢æÛ混合气热处理åQ?/span>1.0%-Pt/CN-BH-HåQ‰ç­‰æ–ÒŽ(gu¨©)³•åˆ¶å¤‡äº?/span>Pt/g-C3N4复合材料。通过XPS表征发现Pt主要ä»?/span>Pt0物种的åŞ式存在于1.0%-Pt/CN-BH-H样品中。相反，Pt主要ä»?/span>Pt2 形式存在äº?/span>1.0%-Pt/CN-På’?/span>1.0%-Pt/CN-BH样品中。经˜q‡æ°¢æ°®æ؜合气氛处理后åQ?/span>Pt的化学状态发生显著变化，1.0%-Pt/CN-BH-Hä¸?/span>Pt0的比例显著增加ã€?/span>1.0%-Pt/CN-P, 1.0%-Pt/CN-BHå’?1.0%-Pt/CN-BH-Hä¸?/span>Pt0的比例分别äØ“8.2%åQ?/span>10.0%å’?/span>60.1%åQˆå›¾1cåQ‰ã€‚经˜q‡æ°”氛处理后åQ?/span>N元素向高¾l“合能方向移动，Pt元素向低¾l“合能方向移动，表明ç”?sh¨´)子ä?/span>Nå?/span>Pt0转移åQˆå›¾1båQ?/span>。这些结果表明，1.0%-Pt/CN-BH-H中含有大量的Pt0物种有利于电(sh¨´)èïLš„分离和è{¿U…R€?/span>通过CO吔R™„¾U¢å¤–光谱åQˆå›¾1dåQ‰å¾—å‡?/span>2115 cm-1处的吔R™„å³?/span>ä¸?/span>COåœ?/span>Pt2 物种上的吔R™„ã€?/span>2055 cm-1处的吔R™„å³?/span>ä¸?/span>COåœ?/span>Pt0物种上的¾U¿æ€§å¸é™„ã€?/span>¾lè¿‡æ°”氛处理后，Pt0物种的比例显著增加。这一¾l“论ä¸?/span>XPS¾l“果保持一è‡?/span>ã€?/span>


å›?/span>1 åQ?/span>aåQ?/span>XPS全谱ã€?/span>样品çš?/span>N 1såQ?/span>båQ‰å’ŒPt 4fåQ?/span>cåQ‰å…ƒç´ è°±ã€?/span>åQ?/span>dåQ‰æ ·å“çš„CO吔R™„¾U¢å¤–光谱ã€?/span>

   在可见光条äšg下，1.0 %-Pt/CN-BH-H 样品åQ?/span>Pt0的比例äØ“60.1%åQ?/span>å…ähœ‰æœ€é«˜çš„光催化活æ€?/span>åQ?/span>2.316 mmol h-1 g-1åQ?/span>åQŒçº¦ä¸?/span>1.0 %-Pt/CN-P 样品åQ?/span>0.605 mmol h-1 g-1 , Pt0的比例äØ“8.2%åQ?/span>å’?/span>1.0%-Pt/CN-BH样品åQ?/span>0.644 mmol h-1 g-1 , Pt0的比例äØ“10.0%åQ?/span>çš?/span>4å€?/span>åQˆå›¾2aåQ?/span>。因此，催化‹zÀL€§ä¸ŽPt物种的化学状态有兟ë€?/span>我们可以认äØ“åQ?/span>1.0%-Pt/CN-BH-Hä¸?/span>Pt0的比ä¾?/span>­‘Šé«˜åQŒå…‰å‚¬åŒ–性能­‘Šå¥½ã€‚通过多次循环实验表明1.0%-Pt/CN-BH-Hå…ähœ‰ä¼˜å¼‚的稳定æ€?/span>åQˆå›¾2båQ‰ã€?/span>1.0%-Pt/CN-BH-Håœ?/span>420 nm下的表观量子效率ä¸?/span>8.1%åQŒæ˜¾è‘—高äº?/span>1.0%-Pt/CN-PåQ?/span>4.0%åQ?/span>åQŒè¯´æ˜Žå‰è€…在可见光条件下å…ähœ‰ä¼˜è¶Šçš„æ´»æ€?/span>åQˆå›¾2cåQ?/span>ã€?/span>


å›?/span>2 ‹zÀL€§æµ‹è¯•ã€‚（aåQ‰æ ·å“åœ¨å¯è§å…‰ï¼ˆÎ» â‰?420 nmåQ‰ä¸‹çš„光催化产氢速率。（båQ?/span>1.0%-Pt/CN- BH-H的光催化产氢循环实验。（cåQ?/span>1.0%-Pt/CN-På’?/span>1.0%-Pt/CN-BH-Håœ?/span>420å’?/span>450 nm处的单æ‡L长表观量子效率ã€?/span>åQ?/span>dåQ‰ä¸å?/span>Pt/g-C3N4复合材料光催化äñ”氢速率的比较ã€?/span>


  ä¸ÞZº†ç ”究不同Pt物种åQ?/span>Pt2 å’?/span>Pt0åQ?/span>ä¸?/span>g-C3N4之间的电(sh¨´)荷分¼›ÀL•ˆçŽ‡ï¼Œæˆ‘们‹¹‹é‡äº?/span>1.0%-Pt/CN-BH-Hå’?/span>1.0%-Pt/CN-P在可见光条äšg下的原位¾U¢å¤–光谱ã€?/span>ä¸?/span>1.0%-Pt/CN-BH-H在黑暗条件下相对较低çš?/span>å³?/span>强相比，随着光照旉™—´çš„增加，特征峰显著提é«?/span>åQ?/span>å›?/span>3aåQ?/span>ã€?/span>822 cm-1处的峰归因于七嗪环的伸羃振动åQ?/span>886 cm-1处的峰归因于N-H键的弯曲振动ã€?/span>åœ?/span>1489å’?/span>1710 cm-1附近的峰分别对应于杂环中çš?/span>-C=Nå’?/span>N-C=NåQŒè€Œåœ¨1338 cm-1附近的峰则来源于-CNçš„äŽ×¾~©ã€‚随着光照旉™—´çš„增加，å³?/span>çš?/span>强度明显增大åQŒå³°ä½ç½®ä¿æŒä¸å˜ã€‚这些结果表明，1.0%-Pt/CN-BH-H样品ä¸?/span>g-C3N4的结构和化学键在可见å…?/span>照射下由于强烈的ç”?sh¨´)子传递而发生明昑֏˜åŒ?/span>。äؓ了比较，我们˜q˜ç ”½I¶äº†1.0%-Pt/CN-P样品åQ?/span>å›?/span>3båQ?/span>ã€?/span>1.0%-Pt/CN-P没有明显的峰çš?/span>å?/span>åŒ?/span>åQŒè¿™å¯èƒ½æ˜¯ç”±äº?/span>Pt2 ä¸?/span>g-C3N4之间的电(sh¨´)子è{¿U»èƒ½åŠ›è¾ƒå·®æ‰€è‡´ã€‚这些结果表明，é«?/span>Pt0比例有利于电(sh¨´)èïLš„分离和äñ”氢活性的提高ã€?/span>


  ä¸ÞZº†æ­ç¤º1.0%-Pt/CN-BH-Hä¸?/span>Pt0çš„åŞ成机理，采用原位¾U¢å¤–光谱模拟äº?/span>1.0%-Pt/CN-BH的氢氮æØœå?/span>气氛处理˜q‡ç¨‹ã€‚如å›?/span>3cå’?/span>3d所½Cºï¼ŒC-N杂环ä¸?/span>C-N键的峰在1200-1750 cm-1范围内显著增加。随着焙烧温度的升高，C-N键的振动模式发生改变åQ?/span>1710 cm-1处的峰强度逐渐增强åQŒè¡¨æ˜?/span>C3N4¾l“æž„ä¸?/span>N元素的电(sh¨´)负性发生改å?/span>åQ?/span>å›?/span>3dåQ?/span>。这些结果证实了在气æ°?/span>处理˜q‡ç¨‹ä¸­ï¼Œå½“电(sh¨´)子从N元素转移åˆ?/span>Ptæ—Óž¼Œå¤§é‡çš?/span>Pt2 转变ä¸?/span>Pt0物种ã€?/span>å› æ­¤åQŒæˆ‘们可以推æ–?/span>1710 cm-1处峰å¼?/span>的变化是ç”׃ºŽC-Né”?/span>键能的变化，表明g-C3N4¾l“æž„ä¸?/span>N元素ç”?sh¨´)负性的变化。这些结果证å®?/span>åœ?/span>气氛焙烧˜q‡ç¨‹ä¸­ï¼Œå¤§é‡çš?/span>Pt2 通过N元素的吸引电(sh¨´)子è{化äØ“Pt0物种ã€?/span>


å›?/span>3 原位¾U¢å¤–表征ã€?/span>åQ?/span>aåQ?/span>1.0%-Pt/CN-BH-H和（båQ?/span>1.0%-Pt/CN-P在可见光åQ?/span>λ â‰?420 nmåQ?/span>照射下的原位¾U¢å¤–光谱ã€?/span>åQ?/span>cåQ?/span>1.0%-Pt/CN-BH在气氛处ç?/span>和加çƒ?/span>˜q‡ç¨‹ä¸­çš„原位¾U¢å¤–光谱å’?/span>åQ?/span>dåQ?/span>局部放大图ã€?/span>


  ä¸ÞZº†˜q›ä¸€æ­¥ç ”½I?/span>Pt物种的媄响，我们建立äº?/span>Ptä¸?/span>g-C3N4åQ?/span>å›?/span> 4aå’?4dåQ?/span>之间的优化结构模型。该模型代表了不同结构模型对应的Pt的不同配位模式和状态，包括Pt2 å’?/span>Pt0物种。电(sh¨´)荷密度差图显½CÞZº†ç”?sh¨´)子密度的大ž®ï¼Œå¦‚å›?/span>4bå’?/span>4e所½Cºã€‚æ ¹æ?/span>Baderç”?sh¨´)荷分析åQŒåœ¨Pt2 物种存在下，ç”?sh¨´)子ä?/span>Ptå?/span>g-C3N4转移åQŒè{¿U»é‡ä¸?/span>1.24。当存在Pt0物种æ—Óž¼Œç”?sh¨´)子ä?/span>g-C3N4转移åˆ?/span>PtåQŒè{¿U»é‡ä¸?/span>0.68。这些结果表明，Pt2 物种的存在不利于ç”?sh¨´)子的捕莗÷€?/span>åœ?/span>1.0%-Pt/CN-BH-H样品ä¸?/span>åQ?/span>ç”׃ºŽPt0物种比例较高åQŒä¸”Pt0çš?/span>ç”?/span>成提高了ç”?sh¨´)荷分离效率åQ?/span>g-C3N4上的ç”?sh¨´)子更高效地转移å?/span>Pt上ã€?/span>Pt在不同化学状态下å¯ÒŽ(gu¨©)°¢æ°”的吔R™„能如å›?/span>4cå’?/span>4f所½Cºã€?/span>通过计算得到Pt2 å’?/span>Pt0的吸附能分别ä¸?/span>-0.105å’?/span>-0.098 eVã€?/span>Pt2 å’?/span>Pt0的吸附距¼›Õdˆ†åˆ«äØ“2.63å’?/span>2.79 ?。由äº?/span>Pt0物种å…ähœ‰è¾ƒä½Žçš„吸附能åQŒåœ¨å«æœ‰Pt0物种的催化剂中，æ°?/span>æ°?/span>更容易溢出。因此，我们可以得出增加Pt0物种含量有利于析氢。这一¾l“果也与上述原位¾U¢å¤–光谱的结è®ÞZ¸€è‡´ã€‚此外，˜q˜è¯´æ˜Žäº†Pt0物种在光催化制氢中的优越性ã€?/span>


å›?/span>4 DFT理论计算。（aåQ?/span>dåQ?/span>优化¾l“æž„åQ?/span>åQ?/span>båQ?/span>eåQ?/span>å·?/span>åˆ?/span>ç”?sh¨´)荷密度å?/span>åQ?/span>cåQ?/span>fåQ?/span>Pt2 å’?/span>Pt0物种å¯ÒŽ(gu¨©)°¢æ°?/span>的吸附能ã€?/span>


  本研½I¶æˆåŠŸåˆ¶å¤‡äº†é«?/span>Pt0比例åQ?/span>60.1%åQ?/span>的光催化剂ã€?/span>它的光催化äñ”氢速率辑ֈ°2.316 mmol h-1 g-1åQŒæ¯”可见光照ž®?/span>åQ?/span>λ â‰?420 nmåQ?/span>ä¸?/span>Pt0比例较低åQ?/span>8.2%åQ?/span>çš?/span>1.0%-Pt/CN-PåQ?/span>0.605 mmol h-1 g-1åQ?/span>提高äº?/span>4倍ã€?/span>1.0%-Pt/CN-BH-H的高光催化性能可归因于其中含有大量çš?/span>Pt0物种åQŒåŠ é€Ÿäº†å…‰ç”Ÿç”?sh¨´)荷的分¼?/span>ã€?/span>另外åQ?/span>Pt0物种较低的吸附能有利于氢气的溢出。因此，调控化学状态可能是开发新型光催化剂的有效½{–ç•¥ã€?/span>


论文½W¬ä¸€ä½œè€…äؓ中国çŸÏxÑa大学åQˆåŒ—京）博士生武ä½Ïx˜ŸåQŒè®ºæ–‡é€šè®¯ä½œè€…äؓ中国çŸÏxÑa大学åQˆåŒ—京）王雅君副研究员和清华大学朱永法教授。此研究得到国家重点研发计划½{‰èµ„助支持ã€?/span>


原文链接

https://www.sciencedirect.com/science/article/pii/S1385894722018290

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