Zhang Kan, Liu Jiali, Wang Luyang, Jin Bingjun, Yang Xiaofei, Zhang Shengli, Park Jong Hyeok
Institute of Optoelectronics & Nanomaterials, MIIT Key Laboratory of Advanced Display Material and Devices, College of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.
College of New Materials and New Energies, Shenzhen Technology University, Shenzhen, Guangdong 518118, P. R. China.
J Am Chem Soc. 2020 May 13;142(19):8641-8648. doi: 10.1021/jacs.9b13410. Epub 2020 Mar 19.
Solar energy-assisted water oxidative hydrogen peroxide (HO) production on an anode combined with H production on a cathode increases the value of solar water splitting, but the challenge of the dominant oxidative product, O, needs to be overcome. Here, we report a SnO overlayer coated BiVO photoanode, which demonstrates the great ability to near-completely suppress O evolution for photoelectrochemical (PEC) HO oxidative HO evolution. Based on the surface hole accumulation measured by surface photovoltage, downward quasi-hole Fermi energy at the photoanode/electrolyte interface and thermodynamic Gibbs free energy between 2-electron and 4-electron competitive reactions, we are able to consider the photoinduced holes of BiVO that migrate to the SnO overlayer kinetically favor HO evolution with great selectivity by reduced band bending. The formation of HO may be mediated by the formation of hydroxyl radicals (OH·), from 1-electron water oxidation reactions, as evidenced by spin-trapping electron paramagnetic resonance (EPR) studies conducted herein. In addition to the HO oxidative HO evolution from PEC water splitting, the SnO/BiVO photoanode can also inhibit HO decomposition into O under either electrocatalysis or photocatalysis conditions for continuous HO accumulation. Overall, the SnO/BiVO photoanode achieves a Faraday efficiency (FE) of over 86% for HO generation in a wide potential region (0.6-2.1 V vs reversible hydrogen electrode (RHE)) and an HO evolution rate averaging 0.825 μmol/min/cm at 1.23 V vs RHE under AM 1.5 illumination, corresponding to a solar to HO efficiency of ∼5.6%; this performance surpasses almost all previous solar energy-assisted HO evolution performances. Because of the simultaneous production of HO and H by solar water splitting in the PEC cells, our results highlight a potentially greener and more cost-effective approach for "solar-to-fuel" conversion.
阳极上太阳能辅助水氧化生成过氧化氢（HO）并与阴极上的氢气生成相结合，提高了太阳能水分解的价值，但需要克服主要氧化产物氧气（O）带来的挑战。在此，我们报道了一种涂覆有SnO覆盖层的BiVO光阳极，它具有近乎完全抑制光电化学（PEC）HO氧化生成HO过程中析氧的强大能力。基于通过表面光电压测量的表面空穴积累、光阳极/电解质界面处向下的准空穴费米能以及2电子和4电子竞争反应之间的热力学吉布斯自由能，我们能够认为迁移到SnO覆盖层的BiVO光生空穴通过降低的能带弯曲在动力学上有利于以高选择性生成HO。本文进行的自旋捕获电子顺磁共振（EPR）研究表明，HO的形成可能由1电子水氧化反应形成的羟基自由基（OH·）介导。除了PEC水分解产生的HO氧化生成HO外，SnO/BiVO光阳极在电催化或光催化条件下还能抑制HO分解为O，以实现HO的持续积累。总体而言，SnO/BiVO光阳极在宽电位范围（相对于可逆氢电极（RHE）为0.6 - 2.1 V）内实现了超过86%的HO生成法拉第效率（FE），在1.23 V vs RHE、AM 1.5光照下HO生成速率平均为0.825 μmol/min/cm²，对应太阳能到HO的效率约为5.6%；该性能超过了几乎所有先前的太阳能辅助HO生成性能。由于PEC电池中太阳能水分解同时产生HO和H，我们的结果突出了一种潜在更绿色、更具成本效益的“太阳能到燃料”转化方法。
