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  贵金?span style="font-family:;">Pt因其h合适的费米能而被用作常用的助催化剂，hzL高、稳定性好{优ѝ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Q但q种影响未得到深入研究。更为重要的是，了解Pt在光催化反应q程中的真实性质Q可以ؓ(f)构徏h高活性的光催化剂提供新的思\?/span> q期Q中国石油大学（北京Q王雅君副研I员Nl与清华大学朱永法教授在?/span>Chemical Engineering Journal?/span>期刊上发表了题ؓ(f)?/span>Boosting photocatalytic hydrogen evolution via regulating Pt chemical states”的文章Q?span style="font-family:;">DOIQ?/span>10.1016/j.cej.2022.136334Q。本论文提出了一U有效的{略Q通过调节Pt的化学状态来大幅度提?/span>Pt/g-C3N4光催化剂的氢性能。文中制备了不同Pt0含量?/span>Pt/g-C3N4催化剂，发现提高Pt0含量可以大幅提高光解水氢活性。原位红外光谱和DFT理论计算证明Q气?/span>处理使电(sh)子从g-C3N4?/span>N原子转移?/span>Pt2 ?/span>Q从而增加了Pt0物种的数量?/span>Pt0物种的大量生成有利于加速光生电(sh)L(fng)分离。此外，Pt0?/span>Pt2 h更低的氢气吸附能Q有利于氢气的溢出。因此，h高比?/span>Pt0的光催化剂具有更高的产氢zL?/span>


  本文采用了高温热聚合、超声湿渍Q?/span>1.0%-Pt/CNQ、光沉积Q?/span>1.0%-Pt/CN-PQ?/span>NaBH4液相q原Q?/span>1.0%-Pt/CN-BHQ和氢混合气热处理Q?/span>1.0%-Pt/CN-BH-HQ等Ҏ(gu)制备?/span>Pt/g-C3N4复合材料。通过XPS表征发现Pt主要?/span>Pt0物种的Ş式存在于1.0%-Pt/CN-BH-H样品中。相反，Pt主要?/span>Pt2 形式存在?/span>1.0%-Pt/CN-P?/span>1.0%-Pt/CN-BH样品中。经q氢氮؜合气氛处理后Q?/span>Pt的化学状态发生显著变化，1.0%-Pt/CN-BH-H?/span>Pt0的比例显著增加?/span>1.0%-Pt/CN-P, 1.0%-Pt/CN-BH?1.0%-Pt/CN-BH-H?/span>Pt0的比例分别ؓ(f)8.2%Q?/span>10.0%?/span>60.1%Q图1cQ。经q气氛处理后Q?/span>N元素向高l合能方向移动，Pt元素向低l合能方向移动，表明?sh)子?/span>N?/span>Pt0转移Q图1bQ?/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)L(fng)分离和{UR?/span>通过CO吔RU外光谱Q图1dQ得?/span>2115 cm-1处的吔R?/span>?/span>CO?/span>Pt2 物种上的吔R?/span>2055 cm-1处的吔R?/span>?/span>CO?/span>Pt0物种上的U性吸附?/span>l过气氛处理后，Pt0物种的比例显著增加。这一l论?/span>XPSl果保持一?/span>?/span>


?/span>1 Q?/span>aQ?/span>XPS全谱?/span>样品?/span>N 1sQ?/span>bQ和Pt 4fQ?/span>cQ元素谱?/span>Q?/span>dQ样品的CO吔RU外光谱?/span>

   在可见光条g下，1.0 %-Pt/CN-BH-H 样品Q?/span>Pt0的比例ؓ(f)60.1%Q?/span>h最高的光催化活?/span>Q?/span>2.316 mmol h-1 g-1Q?/span>Q约?/span>1.0 %-Pt/CN-P 样品Q?/span>0.605 mmol h-1 g-1 , Pt0的比例ؓ(f)8.2%Q?/span>?/span>1.0%-Pt/CN-BH样品Q?/span>0.644 mmol h-1 g-1 , Pt0的比例ؓ(f)10.0%Q?/span>?/span>4?/span>Q图2aQ?/span>。因此，催化zL与Pt物种的化学状态有兟?/span>我们可以认ؓ(f)Q?/span>1.0%-Pt/CN-BH-H?/span>Pt0的比?/span>高Q光催化性能好。通过多次循环实验表明1.0%-Pt/CN-BH-Hh优异的稳定?/span>Q图2bQ?/span>1.0%-Pt/CN-BH-H?/span>420 nm下的表观量子效率?/span>8.1%Q显著高?/span>1.0%-Pt/CN-PQ?/span>4.0%Q?/span>Q说明前者在可见光条件下h优越的活?/span>Q图2cQ?/span>?/span>


?/span>2 zL测试。（aQ样品在可见光（λ ?420 nmQ下的光催化产氢速率。（bQ?/span>1.0%-Pt/CN- BH-H的光催化产氢循环实验。（cQ?/span>1.0%-Pt/CN-P?/span>1.0%-Pt/CN-BH-H?/span>420?/span>450 nm处的单L长表观量子效率?/span>Q?/span>dQ不?/span>Pt/g-C3N4复合材料光催化氢速率的比较?/span>


  Z研究不同Pt物种Q?/span>Pt2 ?/span>Pt0Q?/span>?/span>g-C3N4之间的电(sh)荷分L率，我们量?/span>1.0%-Pt/CN-BH-H?/span>1.0%-Pt/CN-P在可见光条g下的原位U外光谱?/span>?/span>1.0%-Pt/CN-BH-H在黑暗条件下相对较低?/span>?/span>强相比，随着光照旉的增加，特征峰显著提?/span>Q?/span>?/span>3aQ?/span>?/span>822 cm-1处的峰归因于七嗪环的伸羃振动Q?/span>886 cm-1处的峰归因于N-H键的弯曲振动?/span>?/span>1489?/span>1710 cm-1附近的峰分别对应于杂环中?/span>-C=N?/span>N-C=NQ而在1338 cm-1附近的峰则来源于-CN的׾~。随着光照旉的增加，?/span>?/span>强度明显增大Q峰位置保持不变。这些结果表明，1.0%-Pt/CN-BH-H样品?/span>g-C3N4的结构和化学键在可见?/span>照射下由于强烈的?sh)子传递而发生明昑֏?/span>。ؓ(f)了比较，我们q研I了1.0%-Pt/CN-P样品Q?/span>?/span>3bQ?/span>?/span>1.0%-Pt/CN-P没有明显的峰?/span>?/span>?/span>Q这可能是由?/span>Pt2 ?/span>g-C3N4之间的电(sh)子{U能力较差所致。这些结果表明，?/span>Pt0比例有利于电(sh)L(fng)分离和氢活性的提高?/span>


  Z揭示1.0%-Pt/CN-BH-H?/span>Pt0的Ş成机理，采用原位U外光谱模拟?/span>1.0%-Pt/CN-BH的氢氮؜?/span>气氛处理q程。如?/span>3c?/span>3d所C，C-N杂环?/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Q?/span>1710 cm-1处的峰强度逐渐增强Q表?/span>C3N4l构?/span>N元素的电(sh)负性发生改?/span>Q?/span>?/span>3dQ?/span>。这些结果证实了在气?/span>处理q程中，当电(sh)子从N元素转移?/span>PtӞ大量?/span>Pt2 转变?/span>Pt0物种?/span>因此Q我们可以推?/span>1710 cm-1处峰?/span>的变化是׃C-N?/span>键能的变化，表明g-C3N4l构?/span>N元素?sh)负性的变化。这些结果证?/span>?/span>气氛焙烧q程中，大量?/span>Pt2 通过N元素的吸引电(sh)子{化ؓ(f)Pt0物种?/span>


?/span>3 原位U外表征?/span>Q?/span>aQ?/span>1.0%-Pt/CN-BH-H和（bQ?/span>1.0%-Pt/CN-P在可见光Q?/span>λ ?420 nmQ?/span>照射下的原位U外光谱?/span>Q?/span>cQ?/span>1.0%-Pt/CN-BH在气氛处?/span>和加?/span>q程中的原位U外光谱?/span>Q?/span>dQ?/span>局部放大图?/span>


  Zq一步研I?/span>Pt物种的媄响，我们建立?/span>Pt?/span>g-C3N4Q?/span>?/span> 4a?4dQ?/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 ?/span>Pt0物种。电(sh)荷密度差图显CZ?sh)子密度的大，如?/span>4b?/span>4e所C。根?/span>Bader?sh)荷分析Q在Pt2 物种存在下，?sh)子?/span>Pt?/span>g-C3N4转移Q{U量?/span>1.24。当存在Pt0物种Ӟ?sh)子?/span>g-C3N4转移?/span>PtQ{U量?/span>0.68。这些结果表明，Pt2 物种的存在不利于?sh)子的捕莗?/span>?/span>1.0%-Pt/CN-BH-H样品?/span>Q?/span>׃Pt0物种比例较高Q且Pt0?/span>?/span>成提高了?sh)荷分离效率Q?/span>g-C3N4上的?sh)子更高效地转移?/span>Pt上?/span>Pt在不同化学状态下Ҏ(gu)气的吔R能如?/span>4c?/span>4f所C?/span>通过计算得到Pt2 ?/span>Pt0的吸附能分别?/span>-0.105?/span>-0.098 eV?/span>Pt2 ?/span>Pt0的吸附距d别ؓ(f)2.63?/span>2.79 ?。由?/span>Pt0物种h较低的吸附能Q在含有Pt0物种的催化剂中，?/span>?/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l果也与上述原位U外光谱的结Z致。此外，q说明了Pt0物种在光催化制氢中的优越性?/span>


?/span>4 DFT理论计算。（aQ?/span>dQ?/span>优化l构Q?/span>Q?/span>bQ?/span>eQ?/span>?/span>?/span>?sh)荷密度?/span>Q?/span>cQ?/span>fQ?/span>Pt2 ?/span>Pt0物种Ҏ(gu)?/span>的吸附能?/span>


  本研I成功制备了?/span>Pt0比例Q?/span>60.1%Q?/span>的光催化剂?/span>它的光催化氢速率辑ֈ2.316 mmol h-1 g-1Q比可见光照?/span>Q?/span>λ ?420 nmQ?/span>?/span>Pt0比例较低Q?/span>8.2%Q?/span>?/span>1.0%-Pt/CN-PQ?/span>0.605 mmol h-1 g-1Q?/span>提高?/span>4倍?/span>1.0%-Pt/CN-BH-H的高光催化性能可归因于其中含有大量?/span>Pt0物种Q加速了光生?sh)荷的分?/span>?/span>另外Q?/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{略?/span>


论文W一作者ؓ(f)中国xa(b)大学Q北京）博士生武xQ论文通讯作者ؓ(f)中国xa(b)大学Q北京）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{资助支持?/span>


原文链接

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

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